Unit 2Atoms & Elements

What is matter?

MATTER• Mass • Volume

MASS• How much matter

is in an object • G, kg, mg

Volume• How much space

something takes up • L, mL

States of Matter

Changes in StateMelting: Solid ! Liquid

Freezing: Liquid ! Solid

Note: Melting Point = Freezing Point

Evaporation: Liquid ! Gas

Condensation: Gas ! Liquid

Sublimation: Solid ! Gas

Deposition: Gas ! Solid

The Particle Theory of Matter• Created to describe the structure

and behaviour of matter

5 Points of The Particle Theory of Matter

1. All matter is made up of tiny particles

5 Points of The Particle Theory of Matter

2. All particles have spaces between them

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

5 Points of The Particle Theory of Matter4. The particles are always moving. The more energy

the particles have, the faster they move. 5. There are attractive forces between the particles.

The forces are stronger when the particles are closer together

The Particle Theory of Matter& Changes in State

• As energy is added to the particles, they move around more.

• Bonds between particles weaken

• When the particles can slide past each other, the substance is now a liquid

• When the particles are no longer bonded to each other and are flying around randomly, the substance is now a gas

The Particle Theory of Matter& Changes in State

THE HISTORY OF MATTER

Ancient Greek Philosophers• Did almost no

experimentation • Empedocles proposed

matter was composed of 4 elements

• Democritus suggested matter was made up of “atomos”, which means indivisible

• Socrates and Aristotle rejected Democritus’ ideas.

Alchemists• First to perform experiments • 3 main goals:

1. To change base metals into valuable ones (ex. Gold) 2. To find the substance that would give them eternal

life 3. To produce a universal solvent that would dissolve

all substances

Modern Chemists• Used scientific method & focused

on determining the properties and composition of pure substances

• Sir Francis Bacon one of the first to develop new knowledge from experimentation

• Boyle aimed to improve 4-element theory

• Lavoisier defined “element” and identified 23 different elements through measurement and observations

What is an atom?

What is an atom?• The smallest particle of any

type of matter

• Shape: Spherical

• Size: 10-10 m

• Consists of: subatomic particles called nucleus, protons, neutrons, electrons

Skydome in Toronto = Atom Baseball = Nucleus Marbles inside baseball = Protons Mosquitoes buzzing around baseball = Electrons

Subatomic Particle

Symbol and Charge Mass Location

Proton p+ 1 amu nucleus

Neutron n 1 amu nucleus

Electron e- 1/1837 amu electron shell

Who discovered the atom?

• Democritus: “Atomos” • Dalton: All elements are

composed of atoms

What are the other models of atoms?

Models of Atomic Structure

Dalton’s Model (1800’s)

• “Billiard ball” model • Atom is a solid, indivisible, indestructible sphere with no

subatomic particles • Each element is composed of 1 type of atom and is

characterized by the mass of its atoms • Joining of atoms of 2 or more elements = a compound • Atoms are not created or destroyed in a chemical change

Thomson’s Model (1904)• “Plum pudding” model • Discovered electrons & protons • Proposed atoms are spherical • Proposed electrons are embedded in sphere

Rutherford’s Model (1911)• Discovered existence of

the nucleus • Proposed nucleus is tiny,

dense and positive core of the atom

• Proposed protons are contained in nucleus

• Proposed nucleus is surrounded by empty space

• “Electron cloud”

Bohr’s Model (1913)• “Planetary” model • Placed electrons in

specific orbits around nucleus

• Electrons move around nucleus in circular paths called orbits

• Electrons more stable when at lower energy levels, closer to the nucleus

Quantum Model• The “wave” model • Explained more complex

atoms • Proposed it is impossible

to determine the exact location of an electron

• Shows how electrons move randomly in orbitals with varying energy levels

• Location of an electron is based on its energy

H Li Be Na

Mg Ca N F Cu

Ne He Al Fe S Cl K U I

H Hydrogen

Li Lithium

Be Beryllium

Na Sodium

Mg Magnesium

N Nitrogen

F Fluorine

Ca Calcium

Cu Copper

Ne Neon

He Helium

Al Aluminum

Fe Iron

S Sulfur

Cl Chlorine

K Potassium

U Uranium

I Iodine

ELEMENTS

What is an element?•A pure substance that

cannot be broken down into simpler substances

•Made up of identical atoms

Naming Elements• Chemical symbol: Abbreviation of

the name of the element

• A single letter symbol is always capitalized. Ex. Carbon = C

• The first letter of a 2-letter symbol is always capitalized, while the second letter is lower case. Ex. Aluminum = Al

Where do the names come from?

• In Latin… • Gold = Aurum • Silver = Argentum • Lead = Plumbum

• Einsteinium = Es

ATOMIC MASS & ATOMIC NUMBER

What information does the Period Table give us?

• Element... • Name • Symbol • Atomic mass • Atomic number

What information does the Period Table give us?

• Atomic mass = • The average mass of

an atom of the element

• The sum of the number of protons and neutrons in the nucleus of an atom

What information does the Period Table give us?

• Atomic number = • The number of

protons in the nucleus of an atom.

What information does the Periodic Table give us?

• # Electrons = Atomic #

• # Protons = Atomic # • # Neutrons = Atomic Mass – Atomic #

Atomic Mass – proton # *Note:

If number of protons are known, you can identify the element since

atomic # = # of protons.

Atomic Notation

• Atomic mass in upper left, superscript

• Chemical Symbol • Atomic number in

lower left, subscript

Ti47.87

22

What is a Bohr model?

& No.. It is not a “Bohring” model!

Remember this diagram?

Bohr Models

• The center contains the number of protons and neutrons

• The outer “shells” consist of electrons

• Exact position of electrons in shells is not important.

• Electrons should be spaced equally

Bohr Models

•1st shell: • Closest to nucleus

• Holds a maximum of 2 electrons

• Must be filled before electrons are placed in 2nd shell

Bohr Models

•2nd shell: • Can hold a maximum of 8 electrons

• Must be filled before electrons are placed in additional shell

Bohr Models

•3rd shell: • Can hold a maximum of 8 electrons

• Must be filled before electrons are placed in additional shell

REACTIVITY• The tendency of a substance to

undergo chemical changes in a system.

REACTIVITY• Number of electrons indicates

REACTIVITY

• All atoms WANT to be stable

• Losing, sharing or gaining electrons is a way to become stable

REACTIVITY• WHEN OUTER SHELL IS FILLED,

ELEMENTS ARE STABLE. • “Outer shell” refers to

outermost shell in Bohr diagram that contains electrons.

Reactive Families

• Alkali metals • Halogens • Alkaline earth metals • Chalcogens

Unreactive

• Noble gases

What is the Periodic Table?

Periodic Table

• Organizes elements in a particular way and can give a great deal of information about an element

• Understanding the organization and plan of the periodic table can help you obtain basic information about the elements

Dmirtri Mendeleev

• 64 elements arranged by atomic mass, and similar physical and chemical properties

• Predicted properties of missing elements

• Left spaces for “undiscovered elements”

Modern Periodic Table• Revised by Moseley’s work with X-

rays

• 109 elements arranged by atomic number

• Incorporated noble gases and elements that didn’t fit their position in terms of properties

Period

• Horizontal rows • 1-7 • Representing electron shell in

the Bohr model and an energy level in the quantum model

Family

• Vertical columns

• 1-18 left to right OR

• I-VIII followed by A or B

• Elements with similar physical and chemical properties

• Same number of electrons in their outermost shell (valence electrons)

Families Periods• Columns

• Similar properties

• Same number of valence electrons

• Horizontal rows

• Elements not alike

• First element in a period is always active solid and last is always inactive gas

*Note Roman Numeral Number

= Number of Valence Electrons

Number of electrons in last shell of Bohr Diagram

= # of Valence Electrons

Periodic Law

Elements arranged according to atomic number resulting in a reoccurring pattern of similar

properties in different elements.

ELEMENTS vs COMPOUNDS

What is a pure substance?• Substance that contains only 1 kind of

particle. A mixture is defined as a substance that contains 2 or more pure substances.

What is a pure substance?• A material that has consistent properties

and constant composition.

• Examples:

• Water • Tin • Sulfur

• Table salt • Sugar • Baking soda

A MOLECULE IS…• Composed of a cluster of atoms and can be

broken down into those atoms during a chemical change.

AN ELEMENT IS…

• A pure substance whose molecules are made up of identical atoms.

A COMPOUND IS…

• A pure substance whose molecules are made of different kinds of atoms. Compounds can be broken down into simpler substances called elements.

Are there elements that are also compounds?

Are there atoms that are also molecules?

PROPERTIES OF SUBSTANCES Why are certain substances used in the

world we live in today?

METALS

• >75% of the elements • Left & centre of periodic

table (mostly) • Physical properties • Shiny, malleable, ductile, solid at

room temperature (except mercury), conduct heat & electricity

NONMETALS

• 15% of the elements • Far-right side of the

periodic table • Physical properties • No lustre • Brittle • Nonconductors or insulators

of heat and electricity • Solid or gas at room

temperature

METALLOIDS• 6% of the elements • Located on the “staircase” of

the periodic table • Properties of metals AND

nonmetals • Physical Properties:

• Solid at room temperature • Some have lustre • Behave like nonmetals (except

conductivity) • Semiconductors

PROPERTIES OF SUBSTANCES• Stability

• Usefulness

• Durability

• Safety

• Accessibility

• Conductivity

PROPERTIES & POLLUTION• The presence in or introduction

into the environment of a substance or thing that has harmful or poisonous effects.

What are some sources of pollution?

Think about air, soil, land, water pollution

What is mother nature to you?

Why do people need nature?

How can you evolve to benefit mother nature?

CHEMICAL & PHYSICAL CHANGES

Physical Changes• The substance remains the same even though it

may change state or form (shape).

• Can be reversible

• Examples: Cutting, tearing, shattering, mixing, blending, changes in state (melting, freezing, boiling, etc)

Chemical Changes• The original substance is changed into one or

more different substances that have different properties.

• Atoms stay the same but molecules are transformed, so the products are different substances than the reactants.

• Examples: Changes in colour or temperature, production of a gas, rotting, burning, cooking, rusting, forming a precipitate

Physical Properties• Colour • Texture • Odour • Lustre • Clarity

• Taste • Hardness • Malleability • Ductility • Solubility

Chemical Properties• Combustibility

• Flammability

• Reaction with acid

• Types of bonds that it will form

• Chemical stability/reactivity

• Oxidation states

Definitions• Reactants: The “ingredients” of a reaction

• Products: The end results

• Combustion: Substance reacts with oxygen and gives off heat.

• Oxidation: Interaction between oxygen and different substances it may contact.

• Pure substance: A sample of matter with definite and constant composition with distinct chemical properties. Ex. Water, table salt, gold.

Definitions• Mixture: A system made up of 2 or more different substances which

are mixed, but not combined chemically. Ex. Mixing salt with pepper.

• Homogenous mixture: A mixture where the components that make up the mixture are uniformly distributed throughout. Composition is the same throughout. You cannot pick out components of homogenous mixtures. Ex. Air, Vinegar

• Heterogenous mixture: A mixture where the components are not uniform or have regions with different properties. Different samples of mixture are not identical to one another. Ex. cereal in milk, pizza, blood, vegetable soup

Definitions• Precipitate: An insoluble solid that emerges from a liquid solution.

• Heat: The form of energy that flows between 2 samples of matter due to their difference in temperature.

• Ductility: A solid material’s ability to deform under stress. Ex: Ability to be stretched into wire.

• Malleability: The ability of a metal to be hammered into thin sheets. Ex. Gold and silver are highly malleable.