Unit 2 Chemistry. Models of Matter: The Particle Theory 2000 years ago a philosopher named Democritus suggested that matter was made up of tiny particles

Unit 2Unit 2

ChemistryChemistry

Models of Matter: The Particle Models of Matter: The Particle TheoryTheory

2000 years ago a philosopher named 2000 years ago a philosopher named Democritus suggested that matter was Democritus suggested that matter was made up of tiny particles too small to be made up of tiny particles too small to be seenseen

If you keep cutting a substance into If you keep cutting a substance into smaller pieces, you will eventually come to smaller pieces, you will eventually come to the smallest possible particles – the the smallest possible particles – the building of blocks of matter. Think of Lego building of blocks of matter. Think of Lego piecespieces

The 4 Principles of the Particle The 4 Principles of the Particle Theory of MatterTheory of Matter

All matter is made up of tiny particles.All matter is made up of tiny particles.

All particles of one substance are the same. All particles of one substance are the same. Different substances are made of different Different substances are made of different particles.particles.

The particles are always moving. The more The particles are always moving. The more energy the particles have, the faster they move. energy the particles have, the faster they move.

There are attractive forces between the particles. There are attractive forces between the particles.

These forces are stronger when the particles are These forces are stronger when the particles are closer together.closer together.

Pure Substances and MixturesPure Substances and Mixtures

There are two categories of There are two categories of substances:substances:– Pure substancesPure substances– MixturesMixtures

Pure SubstancesPure Substances

Contain only one kind of particle.Contain only one kind of particle. Examples:Examples:

– Aluminum foil only contains aluminum Aluminum foil only contains aluminum particlesparticles

– Sugar contains only sugar particlesSugar contains only sugar particles

MixtureMixture

Contains at least two different pure Contains at least two different pure substances.substances.

Examples:Examples:– Hot chocolateHot chocolate– Oreo cookieOreo cookie

Classify the FollowingClassify the Following

Salt and waterSalt and water– SolutionSolution

PizzaPizza– Heterogeneous mixtureHeterogeneous mixture

GarbageGarbage– Heterogeneous mixtureHeterogeneous mixture

AirAir– SolutionSolution

How to Classify MixturesHow to Classify Mixtures

When two pure substances are mixed When two pure substances are mixed together, they may mix smoothly or together, they may mix smoothly or unevenly.unevenly.

If the substances mix well with one If the substances mix well with one another, the mixture is called a solution.another, the mixture is called a solution.

If the particles don’t mix well together If the particles don’t mix well together then we have a heterogeneous mixture.then we have a heterogeneous mixture.

Elements and CompoundsElements and Compounds

Elements are pure substances that cannot Elements are pure substances that cannot be broken down into simpler substances.be broken down into simpler substances.

Elements are the building blocks of Elements are the building blocks of matter!!!matter!!!

Compounds are pure substances that Compounds are pure substances that contain two or more different elements in contain two or more different elements in a fixed proportion. Example: water is Ha fixed proportion. Example: water is H220.0.

Atoms and ElementsAtoms and Elements

Scientists now call the particles in the Scientists now call the particles in the particle theory atoms.particle theory atoms.

Each element is made of only one kind of Each element is made of only one kind of atom.atom.

How many kinds of atoms are there?How many kinds of atoms are there?– Since there are over 100 kinds of elements in Since there are over 100 kinds of elements in

the periodic table, there are over 100 kinds of the periodic table, there are over 100 kinds of atoms.atoms.

MoleculesMolecules Atoms join together in combinations.Atoms join together in combinations.

When two or more atoms join together, a When two or more atoms join together, a molecule is formedmolecule is formed

Molecules can contain two atoms or Molecules can contain two atoms or thousands of atomsthousands of atoms– Water molecules have 2 hydrogen atoms and 1 Water molecules have 2 hydrogen atoms and 1

oxygen atomoxygen atom– Methane gas molecules have one carbon atom Methane gas molecules have one carbon atom

and 4 hydrogen atoms and 4 hydrogen atoms – Acetic acid (vinegar) has 2 C, 2 O, and 4 HAcetic acid (vinegar) has 2 C, 2 O, and 4 H

Guess the MoleculeGuess the Molecule

I have 2 hydrogen atomsI have 2 hydrogen atoms I have 1 oxygen atomI have 1 oxygen atom

I am waterI am water

Guess the MoleculeGuess the Molecule I have 10 hydrogen atomsI have 10 hydrogen atoms I have 2 oxygen atomsI have 2 oxygen atoms I have 7 carbon atomsI have 7 carbon atoms I have 4 nitrogen atomsI have 4 nitrogen atoms I am desired in the morning but avoid me in the I am desired in the morning but avoid me in the

eveningevening Coke and Pepsi have me in commonCoke and Pepsi have me in common I am what makes coffee specialI am what makes coffee special

I am CaffeineI am Caffeine

Guess the MoleculeGuess the Molecule

I have 6 hydrogen atomsI have 6 hydrogen atoms I have 6 oxygen atomsI have 6 oxygen atoms I have 6 carbon atomsI have 6 carbon atoms Everybody needs meEverybody needs me I will keep colds awayI will keep colds away You can get me by eating orangesYou can get me by eating oranges

I am vitamin CI am vitamin C

Guess the MoleculeGuess the Molecule I have 8 hydrogen atomsI have 8 hydrogen atoms I have 4 oxygen atomsI have 4 oxygen atoms I have 9 carbon atomsI have 9 carbon atoms I am used quite often by teachers, usually in pairsI am used quite often by teachers, usually in pairs I am white in colorI am white in color You need water when you use meYou need water when you use me I will make you feel betterI will make you feel better

I am aspirinI am aspirin

Chemical Symbols and FormulasChemical Symbols and Formulas

All elements on the periodic table have All elements on the periodic table have symbols that are recognized world wide.symbols that are recognized world wide.

It does not matter which country or It does not matter which country or language, the element Iron is always language, the element Iron is always identified by “Fe” and Oxygen is “O”.identified by “Fe” and Oxygen is “O”.

The names are not always the same but The names are not always the same but the symbols are. Fe is iron in Canada, fer the symbols are. Fe is iron in Canada, fer in France and Fier in Romania.in France and Fier in Romania.

1. I am used to make wedding rings.1. I am used to make wedding rings. I am number 21.I am number 21. I am what you breath in.I am what you breath in. I have a weight of 22.99I have a weight of 22.99


Alchemists in the middle ages were among Alchemists in the middle ages were among the first to recognize that it would be the first to recognize that it would be convenient to represent chemical convenient to represent chemical substances using symbols.substances using symbols.

In 1808, the English chemist, John Dalton, In 1808, the English chemist, John Dalton, developed a system of symbols to developed a system of symbols to represent many elements and compounds.represent many elements and compounds.– Scientists found Dalton’s system to difficult to Scientists found Dalton’s system to difficult to

use.use.


Today a common set of symbols for elements is accepted Today a common set of symbols for elements is accepted around the world.around the world.

A chemical symbol is an abbreviation of the name of an A chemical symbol is an abbreviation of the name of an element.element.

The names and symbols for elements come from many The names and symbols for elements come from many sources.sources.

– Hydrogen comes from the Greek word for “water-former.”Hydrogen comes from the Greek word for “water-former.”

– Mercury was named after a Roman God but the symbol, Hg, Mercury was named after a Roman God but the symbol, Hg, comes from the Latin word Hydrargyrum for “liquid silver.”comes from the Latin word Hydrargyrum for “liquid silver.”

Chemical Formulas - examplesChemical Formulas - examples

Calcium Carbonate (chalk) – CaCOCalcium Carbonate (chalk) – CaCO33

Sodium Chloride (salt) – NaClSodium Chloride (salt) – NaCl Acetylsalicylic acid (aspirin) – CAcetylsalicylic acid (aspirin) – C99HH88OO44

Acetic acid (vinegar) – CAcetic acid (vinegar) – C22HH44OO22

Special notes:Special notes:– Each symbol in a formula represents an element.Each symbol in a formula represents an element.

– If only one atom of an element is present in the If only one atom of an element is present in the compound, no subscript is used.compound, no subscript is used.

– If more than one atom of an element is used, then the If more than one atom of an element is used, then the symbol is followed by an number indicating how many symbol is followed by an number indicating how many atoms are used. This is called a subscript.atoms are used. This is called a subscript.


Single symbols are used to represent Single symbols are used to represent elements.elements.

Combinations of symbols are used to Combinations of symbols are used to represent compounds. These represent compounds. These combinations are called chemical combinations are called chemical formulas.formulas.

The chemical formula indicates which The chemical formula indicates which elements are present and in what ratio.elements are present and in what ratio.

HomeworkHomework

Answer questions 1 – 5 on page 59.Answer questions 1 – 5 on page 59.

andand

Questions 1,2, and 4 on page 61Questions 1,2, and 4 on page 61

Atoms, Molecules, and the Atoms, Molecules, and the AtmosphereAtmosphere

Every person on the planet earth needs air Every person on the planet earth needs air to breathe. But, have you ever wondered to breathe. But, have you ever wondered what air is made up of?what air is made up of?

Take a minute and write down what you Take a minute and write down what you think makes up air.think makes up air.

Now, write down the corresponding Now, write down the corresponding percentages for each compound of air.percentages for each compound of air.

Atoms, Molecules, and the Atoms, Molecules, and the AtmosphereAtmosphere

Here are the actual components of Here are the actual components of air:air:– OxygenOxygen– NitrogenNitrogen– Argon (Ar)Argon (Ar)

– Carbon dioxide (COCarbon dioxide (CO22))

OxygenOxygen Atoms of oxygen can combine to form two Atoms of oxygen can combine to form two

different molecules:different molecules:

OO2 2 is oxygen gas. It makes up 21% of air.is oxygen gas. It makes up 21% of air.

And OAnd O33 is ozone. It is formed naturally in the upper is ozone. It is formed naturally in the upper layers of the atmosphere.layers of the atmosphere.

Ozone is important since it absorbs most of the Ozone is important since it absorbs most of the ultraviolet radiation from the Sun.ultraviolet radiation from the Sun.

The ozone layer is being destroyed by CFCs or The ozone layer is being destroyed by CFCs or chlorofluorocarbons.chlorofluorocarbons.

NitrogenNitrogen

Nitrogen makes up 78.02% of the Nitrogen makes up 78.02% of the atmosphere.atmosphere.

It is not very reactive, which means It is not very reactive, which means we can inhale it without causing we can inhale it without causing chemical changes in our lungschemical changes in our lungs

We do not want to inhale nitrogen We do not want to inhale nitrogen dioxide since it is a very toxic gas.dioxide since it is a very toxic gas.

ArgonArgon

Argon gas is completely harmless.Argon gas is completely harmless.

Almost all of the argon in the atmosphere Almost all of the argon in the atmosphere has leaked out from inside the Earth.has leaked out from inside the Earth.

Argon is used for filling electric light bulbs Argon is used for filling electric light bulbs and fluorescent tubes.and fluorescent tubes.

Argon and other gases make up 0.94% of Argon and other gases make up 0.94% of the atmosphere.the atmosphere.

Carbon Dioxide (COCarbon Dioxide (CO22))

When fossil fuels burn, the two main When fossil fuels burn, the two main products are carbon dioxide and products are carbon dioxide and water.water.

Carbon dioxide is used by plants.Carbon dioxide is used by plants.

Carbon dioxide makes up 0.03% of Carbon dioxide makes up 0.03% of the atmosphere.the atmosphere.

Carbon Monoxide (CO)Carbon Monoxide (CO) Produced during combustion when there is Produced during combustion when there is

a lack of oxygen. For example, if you use a lack of oxygen. For example, if you use a propane barbecue indoors, or if you run a propane barbecue indoors, or if you run an automobile inside a closed garage.an automobile inside a closed garage.

The CO molecule is similar to the oxygen The CO molecule is similar to the oxygen molecule in that when carbon monoxide molecule in that when carbon monoxide enters the lungs, the body’s red blood enters the lungs, the body’s red blood cells treats it the same as oxygen and cells treats it the same as oxygen and carries it throughout the body. The cells carries it throughout the body. The cells of the body are then starved of the oxygen of the body are then starved of the oxygen they need and you could die.they need and you could die.

Answering Questions about Answering Questions about Various MoleculesVarious Molecules

By looking at the chemical formula of a molecule By looking at the chemical formula of a molecule we can answer a variety of questions such as:we can answer a variety of questions such as:

– Which elements are required to construct the molecule?Which elements are required to construct the molecule?

– How many atoms, of each element are required to How many atoms, of each element are required to construct the molecule? construct the molecule?

– How many atoms, in total, are required to construct the How many atoms, in total, are required to construct the molecule?molecule?

– What is the ratio of each type of atom in the molecule?What is the ratio of each type of atom in the molecule?

– What is the mass of each molecule?What is the mass of each molecule?

An ExampleAn Example CC99HH88OO44 or Aspirin or Aspirin

– Which elements are required to construct the Which elements are required to construct the molecule?molecule?

C = Carbon H = Hydrogen O = OxygenC = Carbon H = Hydrogen O = Oxygen

– How many atoms, in total, are required to How many atoms, in total, are required to construct the molecule?construct the molecule?

9 + 8 + 4 = 21 total atoms in one molecule of Aspirin9 + 8 + 4 = 21 total atoms in one molecule of Aspirin

– How many atoms, of each element, are required How many atoms, of each element, are required to construct the molecule?to construct the molecule?

9 Carbon, 8 Hydrogen, and 4 Oxygen atoms are required 9 Carbon, 8 Hydrogen, and 4 Oxygen atoms are required to construct one molecule of Aspirinto construct one molecule of Aspirin

– What is the ratio of each type of atom in the What is the ratio of each type of atom in the molecule?molecule?

9/21 is Carbon 8/21 is Hydrogen 4/21 is Oxygen9/21 is Carbon 8/21 is Hydrogen 4/21 is Oxygen

– What is the mass of each molecule?What is the mass of each molecule?Mass of one molecule of aspirin is calculated as follows:Mass of one molecule of aspirin is calculated as follows:(atomic mass C) x 9 (12) x 9(atomic mass C) x 9 (12) x 9 108 108(atomic mass H) x 8(atomic mass H) x 8 (1) x 8(1) x 8 8 8(atomic mass O) x 4 (atomic mass O) x 4 (16) x 4(16) x 4 64 64

180180

The atomic mass of one molecule of Aspirin is 180.The atomic mass of one molecule of Aspirin is 180.

An Example – You do it!An Example – You do it!

Theobromine (Chocolate) – CTheobromine (Chocolate) – C77HH88NN44OO22

– Which elements are required to construct the molecule?Which elements are required to construct the molecule?

– How many atoms, in total, are required to construct the How many atoms, in total, are required to construct the molecule?molecule?

– How many atoms, of each element, are required to How many atoms, of each element, are required to construct the molecule?construct the molecule?

– What is the ratio of each type of atom in the molecule?What is the ratio of each type of atom in the molecule?

– What is the mass of each molecule?What is the mass of each molecule?

ANSWERANSWER Theobromine (Chocolate) – CTheobromine (Chocolate) – C77HH88NN44OO22

– Which elements are required to construct the Which elements are required to construct the molecule?molecule?

C = Carbon H = Hydrogen N = Nitrogen O = OxygenC = Carbon H = Hydrogen N = Nitrogen O = Oxygen

– How many atoms, in total, are required to How many atoms, in total, are required to construct the molecule?construct the molecule?

7 + 8 + 4 + 2 = 21 total atoms in one molecule of 7 + 8 + 4 + 2 = 21 total atoms in one molecule of ChocolateChocolate

– How many atoms, of each element, are required How many atoms, of each element, are required to construct the molecule?to construct the molecule?

7 Carbon, 8 Hydrogen, 4 Nitrogen, and 2 Oxygen atoms 7 Carbon, 8 Hydrogen, 4 Nitrogen, and 2 Oxygen atoms are required to construct one molecule of Chocolate.are required to construct one molecule of Chocolate.

– What is the ratio of each type of atom in the What is the ratio of each type of atom in the molecule?molecule?

7/21 is Carbon7/21 is Carbon 8/21 is Hydrogen 4/21 is Nitrogen and 8/21 is Hydrogen 4/21 is Nitrogen and 2/21 is Oxygen2/21 is Oxygen

– What is the mass of each molecule?What is the mass of each molecule?Mass of one molecule of chocolate is calculated as follows:Mass of one molecule of chocolate is calculated as follows:(atomic mass C) x 7(atomic mass C) x 7 (12) x 7(12) x 7 8484(atomic mass H) x 8(atomic mass H) x 8 (1) x 8(1) x 8 8 8(atomic mass N) x 4(atomic mass N) x 4 (14) x 4(14) x 4 5656(atomic mass O) x 2(atomic mass O) x 2 (16) x 2(16) x 2 3232

180180

The atomic mass of one molecule of chocolate is 180.The atomic mass of one molecule of chocolate is 180.

HomeworkHomework

Questions 1, 2, 4 on page 61Questions 1, 2, 4 on page 61

Combining CapacityCombining Capacity

The ability of one element to The ability of one element to combine with another elements is combine with another elements is called the called the combining capacity.combining capacity.

Combining capacity is similar to the Combining capacity is similar to the number of connections that an atom number of connections that an atom can make.can make.

Combining Capacity (cont.)Combining Capacity (cont.)

Each metal and nonmetal has been Each metal and nonmetal has been given a numerical value to indicate given a numerical value to indicate it’s combining capacity.it’s combining capacity.

Consider the following combining Consider the following combining capacities:capacities:– Sodium = 1Sodium = 1– Chlorine = 1Chlorine = 1– Calcium = 2Calcium = 2

How do you think sodium will How do you think sodium will combine with chlorine? combine with chlorine?


Example 1:Example 1:– Since sodium and chlorine both have Since sodium and chlorine both have

combining capacities of 1 they combine combining capacities of 1 they combine as NaCl.as NaCl.

– The compound is called sodium chloride The compound is called sodium chloride (salt).(salt).

Na Cl

How would calcium combine with How would calcium combine with chlorine?chlorine?


Example 2:Example 2:– Since calcium has a combining capacity Since calcium has a combining capacity

of 2 it wants to use both of it’s bonds of 2 it wants to use both of it’s bonds and seeks out 2 chlorine atoms. and seeks out 2 chlorine atoms. Therefore, the final molecule will be Therefore, the final molecule will be CaClCaCl22

– This molecule is named calcium chloride This molecule is named calcium chloride (a type of salt that is put on icy roads)(a type of salt that is put on icy roads)..

Cl ClCa


Example 3:Example 3:– Consider the combining capacities of Consider the combining capacities of

calcium (Ca) = 2 and oxygen (O) = 2.calcium (Ca) = 2 and oxygen (O) = 2.

– How will Ca and O combine to form their How will Ca and O combine to form their molecule, calcium oxide (lime)?molecule, calcium oxide (lime)?

Combining capacity (cont.)Combining capacity (cont.)

Example 3:Example 3:– Since calcium and oxygen both have Since calcium and oxygen both have

combining capacities of 2, they combine combining capacities of 2, they combine as CaO. The two bonds of each element as CaO. The two bonds of each element are attached to each other, therefore are attached to each other, therefore only one atom of each is required.only one atom of each is required.

CaO



aluminum (Al) = 3 and bromine (Br) = 1.aluminum (Al) = 3 and bromine (Br) = 1.

– How will Al and Br combine to form their How will Al and Br combine to form their molecule, aluminum bromide?molecule, aluminum bromide?

AlBrAlBr33

Al

Br

Br Br



aluminum (Al) = 3 and oxygen (O) = 2.aluminum (Al) = 3 and oxygen (O) = 2.

– How will Al and O combine to form their How will Al and O combine to form their molecule, aluminum oxide?molecule, aluminum oxide?

AlAl22OO33

Commonly used in medicationsCommonly used in medications

Al

O

O

O

Al

How Elements Combine SummaryHow Elements Combine Summary

Rule 1: Metals combine with nonmetals in many Rule 1: Metals combine with nonmetals in many compounds.compounds.

Rule 2: Write the name of the metal and the nonmetal Rule 2: Write the name of the metal and the nonmetal second.second.

Rule 3: Change the ending of the nonmetal to “ide”.Rule 3: Change the ending of the nonmetal to “ide”.

Rule 4: Each atom has its own combining capacity.Rule 4: Each atom has its own combining capacity.

Rule 5: Atoms combine so that each can fill its combining Rule 5: Atoms combine so that each can fill its combining capacity.capacity.

HomeworkHomework

Combine the following elementsCombine the following elementsMagnesium and ChlorineMagnesium and Chlorine (Found in sea water)(Found in sea water)

Cesium and OxygenCesium and OxygenLithium and NitrogenLithium and NitrogenPotassium and BrominePotassium and Bromine (Used in Veterinary (Used in Veterinary

Medicine)Medicine)

Questions 1 – 4 on page 65.Questions 1 – 4 on page 65.

Models of MatterModels of Matter

450 BC – A Greek scholar named 450 BC – A Greek scholar named Empedocles proposed the four Empedocles proposed the four “elements” model.“elements” model.

The four elements included:The four elements included:– EarthEarth– AirAir– FireFire– WaterWater


400 BC – Another Greek scholar named 400 BC – Another Greek scholar named Democritus proposed the “atomic” model. Democritus proposed the “atomic” model.

Democritus suggested that matter was Democritus suggested that matter was made of tiny particles that could not be made of tiny particles that could not be broken down further.broken down further.

He called these particles “atoms”, after He called these particles “atoms”, after the Greek word the Greek word atomos,atomos, which means which means “indivisible”“indivisible”

Models of MatterModels of Matter 1808 – English chemist John Dalton suggested a 1808 – English chemist John Dalton suggested a

revised atomic model.revised atomic model.

– All matter is made of atoms which are particles too small All matter is made of atoms which are particles too small to see.to see.

– Each element has its own kind of atom, with its own Each element has its own kind of atom, with its own particular mass.particular mass.

– Compounds are created when atoms of different Compounds are created when atoms of different elements link to form molecules.elements link to form molecules.

– Atoms cannot be created, destroyed, or subdivided in Atoms cannot be created, destroyed, or subdivided in chemical changes.chemical changes.

Models of MatterModels of Matter 1904 – J.J. Thomson suggested another revised 1904 – J.J. Thomson suggested another revised

atomic model called the “raisin-bun” model.atomic model called the “raisin-bun” model.

– Atoms contain particles called electrons.Atoms contain particles called electrons.

– Electrons have a small mass and a negative charge.Electrons have a small mass and a negative charge.

– The rest of the atom is a sphere of positive charge.The rest of the atom is a sphere of positive charge.

– The electrons are embedded in this sphere so that the The electrons are embedded in this sphere so that the resulting atoms are neutral.resulting atoms are neutral.


1911 – Ernest Rutherford, working in 1911 – Ernest Rutherford, working in Montreal developed another revised Montreal developed another revised model, the nuclear model:model, the nuclear model:

– Atoms have a tiny, dense positive core called a Atoms have a tiny, dense positive core called a nucleusnucleus

– The nucleus is surrounded mostly by empty The nucleus is surrounded mostly by empty space, containing rapidly moving negative space, containing rapidly moving negative electrons.electrons.


A Danish physicist, Niels Bohr, proposed a “planetary” A Danish physicist, Niels Bohr, proposed a “planetary” model of the atom.model of the atom.

– Electrons move around the nucleus in a circular path called Electrons move around the nucleus in a circular path called orbits.orbits.

– The farther away the electron is from the nucleus, the greater The farther away the electron is from the nucleus, the greater its energy.its energy.

– Electrons cannot exist between these orbits, but can move Electrons cannot exist between these orbits, but can move from one orbit to another.from one orbit to another.

– The order of filling of electrons in the first three orbits is 2, 8, The order of filling of electrons in the first three orbits is 2, 8, and 8.and 8.

– DID NOT SHOW PROTONS OR NEUTRONSDID NOT SHOW PROTONS OR NEUTRONS

Sample Bohr ModelsSample Bohr Models

H

Nucleus of a Hydrogen Atom (not showing any protons or neutrons

Bohr – Rutherford DiagramsBohr – Rutherford Diagrams

We can combine Rutherford’s nuclear We can combine Rutherford’s nuclear model with Bohr’s planetary model in model with Bohr’s planetary model in diagrams that summarize the diagrams that summarize the numbers and positions of all three numbers and positions of all three subatomic particles in an atom.subatomic particles in an atom.

Bohr – Rutherford DiagramsBohr – Rutherford Diagrams

Tin AtomTin Atom

Sample Bohr – Rutherford Sample Bohr – Rutherford DiagramsDiagrams

Create a diagram Create a diagram for Nitrogenfor Nitrogen

1. Determine the number of 1. Determine the number of electrons (7)electrons (7)

2. Draw the first orbit with the 2. Draw the first orbit with the maximum number of maximum number of electrons allowed (2)electrons allowed (2)

3. Draw the second orbit with 3. Draw the second orbit with the remaining electrons (5)the remaining electrons (5)

4. Draw the nucleus with the 4. Draw the nucleus with the protons and neutronsprotons and neutrons

7p

7n

You Try It (1)You Try It (1)

Create a diagram for MagnesiumCreate a diagram for Magnesium

AnswerAnswer Determine the number of electrons, 12Determine the number of electrons, 12 Draw the first orbit (2)Draw the first orbit (2) Draw the second orbit (8)Draw the second orbit (8) Draw the third orbit (2)Draw the third orbit (2) Draw the nucleus Draw the nucleus

with the protons and with the protons and

neutronsneutrons 12p

12n


Create a diagram for SodiumCreate a diagram for Sodium

AnswerAnswer

Determine the number Determine the number of electrons (11)of electrons (11)

Draw the first orbital Draw the first orbital (2)(2)

Draw the second Draw the second orbital (8)orbital (8)

Draw the third orbital Draw the third orbital (1)(1)

Draw the nucleus with Draw the nucleus with the protons and the protons and neutrons.neutrons.


Create a diagram for NeonCreate a diagram for Neon

AnswerAnswer

Determine the number of Determine the number of electrons (10)electrons (10)

Draw the first orbit (2)Draw the first orbit (2)

Draw the second orbit (8)Draw the second orbit (8)

Draw the nucleus with the Draw the nucleus with the protons and neutrons.protons and neutrons.

10p

10n

Inside the AtomInside the Atom

We have spent a great deal of time We have spent a great deal of time discussing atoms but what do they look discussing atoms but what do they look like?like?

Atoms are particles that are comprised of Atoms are particles that are comprised of smaller particles called subatomic smaller particles called subatomic particlesparticles

Electrons, protons, and neutrons are Electrons, protons, and neutrons are subatomic particles.subatomic particles.

Inside the Atom - ProtonsInside the Atom - Protons Protons are positively charged particles.Protons are positively charged particles.

Protons have a relative mass of 1Protons have a relative mass of 1

Protons are located in the nucleus of the atom.Protons are located in the nucleus of the atom.

Protons are significant because the number of Protons are significant because the number of protons in an atom determines what an atom is.protons in an atom determines what an atom is.– For example, any atom with one proton is a hydrogen For example, any atom with one proton is a hydrogen

atom. Any atom with 29 protons is a copper atom.atom. Any atom with 29 protons is a copper atom.

The atomic number of an element indicates the The atomic number of an element indicates the number of protons in one atom of that element.number of protons in one atom of that element.

Inside the Atom - ProtonsInside the Atom - Protons

Identify the element:Identify the element:– 37 protons37 protons

RubidiumRubidium

– 48 protons48 protonsCadmiumCadmium

– 105 protons105 protonsDubniumDubnium

Inside the Atom - ElectronsInside the Atom - Electrons

Electrons are negatively charged Electrons are negatively charged particles.particles.

Electrons have a relative mass of Electrons have a relative mass of 1/2000 of a proton.1/2000 of a proton.

Electrons travel in regions of space Electrons travel in regions of space around the nucleus of the atom.around the nucleus of the atom.

Inside the Atom - NeutronsInside the Atom - Neutrons Neutrons are neutral particlesNeutrons are neutral particles

Neutrons are neither positively or negatively Neutrons are neither positively or negatively charged.charged.

Like protons, neutrons have a relative mass of 1.Like protons, neutrons have a relative mass of 1.

Like protons, neutrons are found in the nucleus of Like protons, neutrons are found in the nucleus of the atom.the atom.

Experiments conducted by James Chadwick, in Experiments conducted by James Chadwick, in 1932, led to the discovery of the neutron.1932, led to the discovery of the neutron.

Atomic NumberAtomic Number The atomic number tells us the number of The atomic number tells us the number of

protons in one atom to the element.protons in one atom to the element.

The atomic number also tells us the number of The atomic number also tells us the number of electrons in one atom of an element.electrons in one atom of an element.

The number of electrons is equal to the number The number of electrons is equal to the number of protons.of protons.

Example: the atomic number of calcium is 20 Example: the atomic number of calcium is 20 therefore the number of protons is 20 and the therefore the number of protons is 20 and the number of electrons is also 20.number of electrons is also 20.

The Atomic MassThe Atomic Mass The atomic mass tells us the total number of protons and The atomic mass tells us the total number of protons and

neutrons in one atom of the element. neutrons in one atom of the element.

Therefore, if we know the atomic number and the atomic Therefore, if we know the atomic number and the atomic mass we can determine the number of neutrons.mass we can determine the number of neutrons.

Number of neutrons = atomic mass – atomic numberNumber of neutrons = atomic mass – atomic number

Example: the atomic number of calcium is 20 and the atomic Example: the atomic number of calcium is 20 and the atomic mass is 40. Therefore, the number of neutrons is 40 – 20.mass is 40. Therefore, the number of neutrons is 40 – 20.

Sample QuestionsSample Questions For each of the following elements, state the For each of the following elements, state the

number of protons, electrons, and neutrons in number of protons, electrons, and neutrons in one atom.one atom.

SodiumSodium

SeleniumSelenium

FluorineFluorine

HeliumHelium

Sample QuestionsSample Questions

Element Protons Electrons NeutronsElement Protons Electrons Neutrons

SodiumSodium 1111 1111 1212

SeleniumSelenium 3434 3434 4545

FluorineFluorine 9 9 9 9 1010

HeliumHelium 2 2 2 2 2 2

Standard Atomic NotationStandard Atomic Notation Scientists use a special system to communicate information Scientists use a special system to communicate information

about any atom.about any atom.

This system is known as the standard atomic notationThis system is known as the standard atomic notation

This system represents the numbers of subatomic particles.This system represents the numbers of subatomic particles.

Examples:Examples:3535CLCL 2323NaNa1717 1111

The top number is the atomic mass and the bottom number The top number is the atomic mass and the bottom number is the atomic number.is the atomic number.

Standard Atomic NotationStandard Atomic Notation

3535CLCL1717

35 is the atomic mass, 17 is the 35 is the atomic mass, 17 is the atomic number. The number of atomic number. The number of protons is 17, the number of protons is 17, the number of electrons is 17, and the number of electrons is 17, and the number of neutrons is 18.neutrons is 18.

Standard Atomic NotationStandard Atomic Notation

2323NaNa 1717

23 is the atomic mass, 17 is the 23 is the atomic mass, 17 is the atomic number. The number of atomic number. The number of protons is 17, the number of protons is 17, the number of electrons is 17 and the number of electrons is 17 and the number of neutrons is 6.neutrons is 6.

HomeworkHomework

Questions 2 and 3 on page 89.Questions 2 and 3 on page 89.

Organizing the ElementsOrganizing the Elements People often organize things to make them more People often organize things to make them more

useful.useful.– CupboardsCupboards– ClosetsClosets– Study notes for testsStudy notes for tests

Up to the mid-1800’s, scientists were busy Up to the mid-1800’s, scientists were busy discovering new elements.discovering new elements.

Then they tried to organize the elements Then they tried to organize the elements alphabetically. But every time a new element alphabetically. But every time a new element was discovered, the whole list had to be changed.was discovered, the whole list had to be changed.

Organizing the ElementsOrganizing the Elements Other methods of organization were considered but later Other methods of organization were considered but later

discarded.discarded.– State (gas, solid, liquid)State (gas, solid, liquid)– ColorColor– TasteTaste

John Dalton then found a quantity that could be measured John Dalton then found a quantity that could be measured for an element - its atomic massfor an element - its atomic mass

Several scientists then tried to arrange the known elements Several scientists then tried to arrange the known elements by their atomic masses.by their atomic masses.

The best arrangement was produced by a Russian scientist, The best arrangement was produced by a Russian scientist, Dmitri Mendeleev.Dmitri Mendeleev.

Organizing the ElementsOrganizing the Elements Mendeleev began arranging the elements in order Mendeleev began arranging the elements in order

of increasing atomic mass and noticed that many of increasing atomic mass and noticed that many elements shared common properties. These elements shared common properties. These elements typically belonged to the same vertical elements typically belonged to the same vertical column of his table.column of his table.

Mendeleev’s arrangement showed a regular Mendeleev’s arrangement showed a regular pattern. Mendeleev’s periodic law states: If the pattern. Mendeleev’s periodic law states: If the elements are arranged according to their atomic elements are arranged according to their atomic mass, a pattern can be seen in which similar mass, a pattern can be seen in which similar properties occur regularly.properties occur regularly.

Organizing the ElementsOrganizing the Elements Mendeleev’s periodic table was a major breakthrough in the Mendeleev’s periodic table was a major breakthrough in the

understanding of the elements. However, it was discovered understanding of the elements. However, it was discovered later on that using the atomic mass was not the proper way later on that using the atomic mass was not the proper way to organize the elements.to organize the elements.

The key was to use the atomic number or the number of The key was to use the atomic number or the number of protons.protons.

Therefore a new law was born.Therefore a new law was born.

The modern periodic law states: If the elements are The modern periodic law states: If the elements are arranged according to their atomic number, a pattern can arranged according to their atomic number, a pattern can be seen in which similar properties occur regularly.be seen in which similar properties occur regularly.

HomeworkHomework

Questions 1 – 5 on page 108.Questions 1 – 5 on page 108.

Questions 1 – 4 on right side of page Questions 1 – 4 on right side of page 109.109.

Groups of ElementsGroups of Elements

The periodic table is useful since it The periodic table is useful since it organizes the elements according to organizes the elements according to similar properties.similar properties.

The set of elements in the same The set of elements in the same column in the table is called a column in the table is called a chemical group and they share chemical group and they share similar physical and chemical similar physical and chemical properties.properties.

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Unit 2 Chemistry. Models of Matter: The Particle Theory 2000 years ago a philosopher named Democritus suggested that matter was made up of tiny particles