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SNC1D EXAM STUDY

SHEETS

Sustainably, electrostatics and chemistry (part A)

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Table of contents

Sustainability .................................................................................................................................................

Introduction to ecosystems .................................................................................................................... 3

The biotic components of ecosystem .................................................................................................... 4

Recycling of matter ............................................................................................................................... 5

The abiotic components of an ecosystem ............................................................................................. 6

The nitrogen cycle ................................................................................................................................ 7

Habitat, niche and competition ............................................................................................................. 9

Population ecology ............................................................................................................................... 9

Electrostatics .................................................................................................................................................

Introduction to electrostatics ............................................................................................................... 10

Transferring electric charge ................................................................................................................ 12

Insulator/conductor ............................................................................................................................. 14

Definitions and terms .......................................................................................................................... 15

Chemistry.......................................................................................................................................................

Matter and the particle theory ............................................................................................................. 17

Pure substances and elements ............................................................................................................. 17

Structure of the atom, isotopes ,Bohr diagram and ions ..................................................................... 18

The Rutherford-Bohr diagram atom and chemical families ............................................................... 19

Compounds ......................................................................................................................................... 19

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SUSTAINABILTY

INTRODUCTION TO ECOSYSTEMS

The earth is a big ball of rock with a molten core. On the surface of this rock, we find water, air and

soil. And in, on and around this water, air and soil, we find life. Animal life, plant life, and

microscopic life.

Life: The condition that distinguishes organisms from inorganic and dead organisms, being

manifested by the growth through metabolism, reproduction, and the power of adaptation to

environment through changes originating internally.

This thin layer of lie on the surface of the Earth is called the biosphere (“bio” means living).

Lithosphere: the solid parts of the Earth including rocks, soil and even ice.

Hydrosphere: the liquid parts of the Earth including lakes, oceans, rivers, etc.

Atmosphere: the gas and vapour surrounding the Earth.

The interaction of all the organisms in the biosphere with each other and with their environment is

called ecology.

The study of all the interactions in the biosphere is so impossibly big and complex, biologists and

ecologists have separated the surface of the Earth into various regions called biomes.

A biome is defined as a region of the Earth with a particular climate which has a controlling effect on

the types of plants and animals found there. The largest Canadian biomes include the tundra, the

boreal forest (taiga), the temperate deciduous forest, the grasslands, and the mountain biome.

An ecosystem is defined as a grouping of plants, animals, and other organisms interacting with each

other and their environment. Example: meadows, ponds, cities, etc.

An ecosystem involves both living factors and non-living factors. The living factors are called biotic

factors and the non-living factors are called abiotic factors.

The biotic factors are often very dependent on the abiotic factors. The abiotic factors can greatly

affect an organism’s ability to survive in an area. This is sometimes referred to as the range of

tolerance for an organism.

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THE BIOTIC COMPONENTS OF ECOSYSTEMS

All these factors (biotic and abiotic) play important roles in the survival and sustainability of the

ecosystem.

Plants, called producers, are able to produce their own food from the abiotic environment (water,

CO2 (carbon dioxide) and sunlight).

Since they can “feed themselves, they are referred to as autotrophs.

This process of making their own food is called photosynthesis.

Photosynthesis takes place in a series of chemical reactions that take place inside the plant cells.

REACTANTS PRODUCTS

Carbon dioxide + water + light Glucose (sugar) + oxygen

CO2 + H20 + light C6H12O6 + O2

The plants then store this food (sugar) in the form of starch, resulting in growth of the plant, or use it

themselves as a source of energy for their own cells.

The process of breaking apart glucose to release energy for cells is called cellular respiration. Again,

this involves a long series of chemical reactions but can be summarized into the following equation:

REACTANTS PRODUCTS

Glucose (sugar) + oxygen Carbon dioxide + water + energy

C6H12O6 + O2 CO2 + H20 + energy

Both animals and plants use cellular respiration to supply usable energy for their cells.

The animals and microbes, called consumers, rely on plants and other animals for their food energy.

Because consumers require other organisms as their food source, they are referred to as heterotrophs

(eat others).

Herbivores: heterotrophs that eat only plants

Carnivores: consumers that eat only other consumers

Omnivores: those that eat both plants and animals

Decomposers: consumers responsible for breaking down dead material and waste products.

All consumers ultimately rely on plants; plants are an essential part of all ecosystems. Plants could

not survive without animals and microbes... (Supplying minerals in the form of waste products, seed

dispersion, CO2, etc) and of course the abiotic factors (soil, water, sunlight, etc).

All components work together to maintain and sustain a healthy ecosystem. Almost all ecosystems

have a diverse variety of plants, animals and microbes interacting with each other and their

environment.

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The greater the number of plants, animals, and microbes, the greater the biodiversity. If biodiversity

is reduced, this may impact and damage the ecosystem. Ex. Cutting and burning the rainforests, over

fishing, hunting, etc.

Biodiversity: Existence of a wide variety of plant and animal species in their natural environments.

RECYCLING OF MATTER

When the biotic and abiotic components depend on each other, it results in a constant flow of material

from component to component: a sort of natural recycling.

This is necessary because Earth is a closed system. This means that although we have many different

types of atoms (H, O, C, N, etc), we only have a limited quantity of each and we are not getting

anymore.

There is a finite (limited) amount of all matter on Earth so this natural recycling is necessary or we

would run out of some form of matters, resulting in problems.

This constant recycling of atoms and molecules is necessary for all living things. All the atoms have

been in countless other organisms before. Although we are all unique, we are completely recycled

material.

All the atoms in us have been in countless other organisms before. We are completely recycled

material.

THE ABIOTIC COMPONENTS OF AN ECOSYSTEM

The abiotic components in an ecosystem are often the controlling factors, determining the types of

plants, and animals that can survive in that particular ecosystem.

For example, in a desert ecosystem, the amount of sunlight, temperature range (day-night), rainfall (or

lack of), and soil conditions are some of the controlling abiotic factors. These will all play major roles

in determining what species of plants can survive, and thus affects all the other biotic components as

well.

Most plants & animals have a certain range of conditions in which they can survive (called range of

tolerance). If the conditions change beyond their range of tolerance, the organism will not be able to

survive for any extended period of time.

For example, if you don’t supply a house plant with enough water, what will happen to it? What

about if you over-water it? All living things have specific ranges of tolerance for difference abiotic

factors.

Often you will find certain species (plants or animals) within a particular ecosystem but not others.

The reason for this is that the organism probably confronts one or more abiotic factors which are

limiting to its survival.

Soil is usually considered to be an abiotic factor affecting the different plants and animals in the

ecosystem. Soil, itself, can be an ecosystem with abiotic factors (minerals, water, air, etc) and biotic

factors (bacteria, fungi, insects, plants, etc).

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Rich topsoil contains a complex combination of mineral particles, organic matter from dead

vegetation and animal wastes in various stages of decomposition. As well, decomposers (bacteria and

fungi), earthworms, snails, and insects can be found, helping to break down the larger particles, and

helping with the recycling process.

Rich topsoil contains a complex combination of mineral

particles, organic matter from dead vegetation and animal wastes in various stages of decomposition.

As well, decomposers (bacteria and fungi), earthworms, snails, and insects can be found, helping to

break down the larger particles, and helping with the recycling process.

In nature, bedrock breaks apart forming parent material (also called regolith), and this breaks down

further to form the subsoil. Plants require mineral nutrients such as nitrates (NO3), phosphate (PO4),

potassium (K), and calcium (Ca) to be able to grow properly.

Some of these nutrients come from broken down rocks and some come from decomposing matter in

the humus layer. Excess water can result in these minerals being washed down into the eluviation

layer, a process called leaching.

Farmers often add fertilizer to the soil to replace the nutrients that the plants have used up. This can

be in the form of animal wastes (manure) or chemical fertilizer.

If too much fertilizer is applied to the fields, the excess can run off into nearby bodies of water. This

excess fertilizer can result in rapid growth of algae (an aquatic plant) which can quickly damage the

ecosystem. This result is called an algal bloom.

Other activities that can influence an aquatic ecosystem include use of pesticides and herbicides,

industrial pollution, and urban development.

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BIOACCUMULATION

Other activities that can influence an aquatic ecosystem include use of pesticides and herbicides,

industrial pollution, and urban development.

Food chains and food webs are methods to follow the feeding sequence in an ecosystem. They

illustrate the flow of energy and materials from one organism to the next through the ecosystem. A

food chain can also be used to show how some ecological problems occur.

For example: Dan buys a herbicide (weed killer) that has been thoroughly tested and proven safe at

the concentration it is to be used at. He sprays his crop and all seems fine. Each blade of grass absorbs

1 molecule of this chemical…perfectly safe! A grasshopper eats 100 blades of this grass so it now has

100 molecules of this chemical in it’s’ body. Let’s say this is still safe. A frog eats 100 grasshoppers.

It would now have 10 000 molecules of this chemical in its body. A fish eats 100 frogs, and so on…

Notice as we go further along the food chain, the concentration of the chemical is increasing to a

point where it could easily become toxic. And remember, humans are at the end of many food

chains!! This process is known as bioaccumulation and can severely damage a food chain and

ecosystem.

THE NITROGEN CYCLE

One example of the cycling of matter can be seen in the Nitrogen Cycle. Nitrogen is necessary in the

construction of proteins, DNA (genetic material), and other molecules necessary for life.

Nitrogen gas (N2) makes up approximately 79% of the atmosphere. Unfortunately, it is a very stable

and not readily useable.

Converting nitrogen gas into a more useable form (called nitrate NO3-) is known as nitrogen

fixation. There are two ways for nitrogen fixation to occur: lightning or bacteria in the soil.

The large amount of energy released by lightning can cause nitrogen to react with the oxygen in the

air, forming small amounts of nitrates. These nitrates then dissolve with rain or surface water and

move into plants by their roots (entering the biotic components of the ecosystem).

The plants can then use these nitrates to make DNA and/or proteins that can be taken into consumers

when the plants are eaten. Some bacteria in the soil are capable of fixing nitrogen, the main way of

supplying nitrates to ecosystems.

Some of these nitrogen-fixing bacteria can be found in small lumps (called nodules) on the roots of

certain plants (called legumes). Ex. clover, soybeans, peas and alfalfa.

The bacteria create more nitrates than the plants can use, so some remains in the soil for other plants.

Often, when farmers are growing crops, they will plant a field for a season with a legume, to increase

the amount of nitrates in the soil for the next year’s crops.

Nitrogen, once in the biotic environment, will eventually return to the abiotic environment, usually in

the form of waste products or dead organisms. Bacteria in the soil break down the nitrogen-containing

chemicals into simpler chemicals called ammonia (NH3).

Other bacteria convert ammonia into nitrites, and still other bacteria convert nitrites into nitrates,

which can again be used by plants. When farmers fertilize their fields, or we fertilize our lawns, we

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are adding manure or other chemicals which contain ammonia, which again gets converted into

nitrates for the plants.

There are also denitrifying bacteria that can convert nitrates into nitrites and back into nitrogen gas

which is released into the atmosphere. This process is called denitrification, and is carried out by

bacteria that do not require oxygen.

When homeowners aerate their lawns, they are allowing oxygen into the soil, limiting the effect of

these denitrifying bacteria, allowing the nitrates to remain in the lawn for better grass.

These denitrifying bacteria help to maintain the balance between nitrates, nitrates and N2 gas in the

atmosphere, and help to create the cycling of nitrogen.

Some plants, like the venus-fly trap, pitcher plant, and the sundew live in areas (swamps and bogs)

where there is very little nitrate in the soil. They have adapted to this type of environment by getting

their nitrogen from a different source...they use the proteins and DNA from insects that they catch.

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HABITAT, NICHE AND COMPETITION

All species require a habitat and a niche. An organism’s habitat is where it lives. Ex. A deer’s habitat

is the forest.

An organism’s niche is how the organism fits into its ecosystem, all the ways it interacts with both the

biotic and abiotic environment.

Ex. A deer’s niche would be to: eat grass and leaves, take in O2, produce CO2, fertilize the soil,

provide blood for mosquitoes, provide food for wolves, etc.

When two different species share the same habitat and the same niche, competition occurs. They are

competing for the same food source and territory. This can be a good thing because it keeps both

species’ populations under control. This allows for a more diverse food web and ecosystem.

Sometimes, a new species will get into an ecosystem from a completely different ecosystem. This is

referred to as an invasive species. Because this new species has no natural predators in the

ecosystem, the invasive species can out-compete the native species, and can lead to changes in the

ecosystem.

POPULATION ECOLOGY

Ecosystems are composed of communities which are made up of populations of species.

Species: a group of similar individuals who can mate and produce viable (living), fertile (able to

reproduce) offspring.

Population: a group of similar individual (same species) who live in a limited geographic area.

Community: the relationship between groups of different species in an area.

The carrying capacity of an ecosystem is defined as the maximum number of individuals that can be

supported by an ecosystem without damaging that ecosystem. If carrying capacity is exceeded, the

ecosystem may be damaged beyond repair.

There are a number of factors that can affect the size and rate of growth of a population. Ex. available

food, available space, water, reproductive rate, predators, natural disasters, human influence, etc.

Given normal conditions, and no drastic outside factors, a population will tend to reach an

equilibrium and remain fairly constant. This equilibrium allows most ecosystems to become stable

and self-sustaining.

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Even looking at the interactions between predator and prey, we can see a relationship between the

population sizes.

An open population is one in which organisms may enter (immigrate) or leave (emigrate). A closed

population is one in which they cannot. Ex. an island.

Four factors that affect the rate of growth of a population:

Immigration, Emigration, Birth, Death.

ELECTROSTATICS

LESSON: INTRODUCTION TO ELECTROSATICS

- All matter is made up of atoms which are in turn made of particles which have electric charges.

- If an object has no electric charge, it is said to be neutral.

- Two electrically uncharged objects will have no affect on each other.

- An electrically charged object exerts a force on a neutral object, even if they are not touching.

- Electric charges can be either positive or negative.

- Like (the same) charges repel and unlike (different) charges attract.

- This is known as the Law of Electric Charges.

- According to the Rutherford-Bohr Model of the atom, the nucleus of an atom contains positively

charged protons and neutral neutrons.

- Around the nucleus at different energy levels are found the negatively charged electrons.

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- Because the electrons are found at various energy levels (sometimes called shells or orbitals), they

can often be removed easily from an atom whereas the protons and neutrons are trapped in the

nucleus.

- Any transfer of electric charge involves the movement of electrons from one object to another.

- Because the electric charge on an object will often remain for long periods of time, the electricity is

called static electricity (stationary).

- The science of studying static electricity is called electrostatics.

- To determine whether or not charge has been transferred, a device called an electroscope can be used.

This will respond to charged objects but not to uncharged objects.

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LESSON: TRANSFERRING ELECTRIC CHARGE

- There are 3 methods by which objects can gain an electric charge (become charged):

1. friction

2. contact

3. induction

1. Charging By Friction

- Some substances have a strong hold on their electrons and others have a weak hold.

- As a result, when two substances are rubbed together, the substance which has a weak hold on its

electrons will lose some its electrons (and become positively charged).

- The substance which has a stronger hold on its electrons will gain some electrons (it will become

negatively charged).

- When charging by friction, both objects start out neutral and one becomes positive and the other

becomes negative.

- A table was set up called the Electrostatic Series (see the list)

- It is a list of substances showing which ones have a strong hold on their electrons (and will steal

electrons from other substances) and become negatively charged and which have a weak hold on their

electrons (and will lose electrons) and become positively charged.

2. Charging by Contact

- When a charged object comes in contact with a neutral object, there is a transfer of electrons from the

object with the most electrons to the other object.

- This often creates a spark (a shock) as the electrons jump to the other object.

- The other object always receives the same charge as the object that touched it.

- When charging by contact, both objects end up with the same charge as the charging object.

3. Charging By Induction

- If a negatively charged rod is brought near a neutral object, the electrons in the neutral object will be

repelled and the side of the neutral object near the negatively charged rod will become positively

charged and will be attracted.

- If the neutral pith ball is touched on its negative side using another neutral object or wire (called a

ground), the electrons will move over to the new object, leaving the pith ball positively charged.

Notice that the negative rod never touched the pith ball!

Notice that we have given a pith ball a positive charge using a negatively charged rod.

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CHARING BY INDUCTION

CHARING BY CONTACT

NEGATIVE

POSTIVE

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LESSON: INSULATOR/CONDUCTOR

- An insulator is a substance in which electrons cannot move easily from atom to atom.

- If the atoms do gain extra electrons, the electrons remain with the atom until they are removed.

- A conductor is a substance in which electrons can move easily from one atom to another.

- If a conductor gains extra electrons, they move freely along the surface.

- To discharge or neutralize the charge on an object, the object is connected to a conductor which

conducts the excess electric charge away from the object.

- This is often done by connecting the object to the Earth (called grounding), which is a good conductor

and removes the excess electrons.

ELECTROSERIES (TRIBOELECTRIC)

Human hands (usually too moist, though) Very positive

Rabbit Fur

Glass

Human hair

Nylon

Wool

Fur

Lead

Silk

Aluminum

Paper

Cotton

Steel Neutral

Wood

Amber

Hard rubber (ebonite)

Nickel, Copper

Brass, Silver

Gold, Platinum

Polyester

Styrene (Styrofoam)

Saran Wrap

Polyurethane

Polyethylene (like Scotch Tape)

Polypropylene

Vinyl (PVC)

Silicon

Teflon Very negative

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DEFENITONS AND TERMS

Neutral: when an object has no electric charge.

No affect: What two electrically uncharged objects will have on each other.

Law of Electric Charges: When like charges repel and unlike charges attract.

Like: same

Unlike: different

Rutherford-Bohr Model: A model of an atom.

Neutrons: particles inside of the nucleus; neutral. The Rutherford-Bohr Model

Protons: positively charged particles, found in the nucleus (see P.D.M)

Electrons: negatively charged particles, found around the nucleus.

Energy levels/shells/orbitals: the level of energy of an electron, also the distance between the electron to

the nucleus ( not 100% sure on that).

P.D.M: PROTONS DON’T MOVE!!!!! BIGGGIEEEE!

Static electricity: when the electric charge on an object remains for long periods of time; stationary.

Electrostatics: The science of studying static electricity.

Electroscope: a device to determine whether or not charge has been transferred; will respond to charged

objects but not to uncharged objects.

Charging by Friction: When you start out with two neutral objects, and you rub them together. One

becomes positively charged, while the other becomes positively charged, because one is losing while the

other is gaining electrons.

Positively charged: When the substance loses some electrons.

Negatively charged: When the substance gains electrons.

Electrostatic series: a list of substances showing which ones have a strong hold on their electrons, and

which have a weak hold on their electrons.

Spark: a shock.

Ground: another neutral object or wire that connects somehow to the ground, either sending in or sending

out electrons.

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Charging by Contact: When a charged object comes in contact with a neutral object, creating a transfer

of electrons from the object with the most electrons to the other object (often creating a spark).

Charging by Induction: When a neutral object is brought near a charged object, then grounded, and the

ground is removed, without the charged object touching the neutral object.

Grounding: when you connect the charged object to the Earth.

Discharge/neutralize: when you connect the object to a conductor which conducts the excess electric

charge away from the object, or conduct electrons in.

Conductor: a substance in which electrons can move easily from one atom to another.

Insulator: a substance in which electrons cannot move easily from atom to atom.

Lightning rod: a metal rod or wire attached to a building to prevent lightning damage by conduction the

electrons to the ground.

Electrostatic precipitator: a device to control air pollution using stationary electric charges.

Thunder: The sound made by lightning.

Lightning: in the sky, a flash of bright light caused by the discharge of electricity between clouds, or

between clouds and the ground.

Static cling: the tendency for objects to stick/cling to other objects, when the two objects are oppositely

charged.

Electrostatic spray painting: spray painting by charging the object being painted positively, and

spraying it with negatively charged paint leaving the nozzle, attracted to the positive target. Gives a

smooth thin layer of paint, and ensures that the surface is thoroughly covered.

Van de Graaff generator (VDG): an electrostatic generator.

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CHEMISTRY

Matter and the Particle Theory

- Matter is anything that has mass and takes up space.

- To determine what type of matter something is, we use our senses and we make observations about

the matter.

- These observations are called properties.

- We study the properties of matter to determine how it behaves and this helps us to know how to deal

with the matter.

- All matter has certain things in common and these have been combined together to form the Particle

Theory of Matter.

- The Particle Theory of Matter helps us understand about the properties of all types of matter.

The Particle Theory of Matter

All matter is made up of small particles.

All particles of a pure substance are identical to each other and different from another pure

substance.

All particles are constantly moving.

Particles attract each other.

Particles at higher temperatures (more energy) move faster than particles at lower temperatures.

Pure Substances and Elements

- Matter can be classified into two categories: pure substances and mixtures.

- A pure substance is composed of only one substance, unlike mixtures which can be a combination of

many pure substances.

- Any sample of a pure substance would have the same composition and properties

- There are two forms of pure substances: elements and compounds

- Pure substance: A substance is pure only if it has the same composition throughout the sample.

- It’s components cannot be separated by physical methods.

- Element: pure substance that cannot be broken down into simpler substances by ordinary physical or

chemical means. They are the basic building blocks of all matter.

- Each element has its own characteristic proprieties.

- Smallest thing an element can be dvided up into is an atom.

- With the exception of mercury, most of the 118 elements are classified as metals (shiny an good

conductors), and are solid.

- The other elements are classified as the non metals.

- Many are gasses at room temperature.

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- Each different element has a chemical symbol/abbreviation, consisting of a single/2 letters (some

have 3), the first in which is always capitalized. Eg. Hydrogen = H, Sodium = Na.

Structure of the Atom, Isotopes, Bohr Diagrams and Ions

- An atom has a nucleus which contains positively charged particles called protons, and neutral

particles called neutrons.

- Electrons are negatively charged particles, surrounding the nucleus.

- it takes 1,836 electrons to equal the mass of one proton.

- Protons and neutrons are the same mass/size (about).

- The atomic number is the number of protons in an atom. Eg. Hydrogen (H) 1, Gold (Au) 79.

- The atomic mass of an element is the sum of protons and neutrons in the nucleus.

- Subtract the atomic number from the atomic number to find the number of neutrons.

- A neutral atom has the same number of protons and electrons.

- Eg. Carbon (C) is number 6 (atomic number). That means it has six protons and 6 electrons…. The

atomic mass is 12 so that means it has 6 neutrons (12-6=6).

- Although all the atoms of an element have the same number of protons (same atomic number), they

may have different numbers of neutrons.

- Atoms with the same number of protons but a different number of neutrons are called isotopes.

- Electrons circle around the nucleus, and they are found at certain energy levels/shells (each shell is a

different distance from the nucleus). Atoms have layers.

- The first energy level can hold a maximum of 2 electrons. The 2nd

energy level can hold 8, the 3rd

hold 18 and the 4th holds 32 electrons. (MAXIUM OF EACH).

- The closest energy gets filled first (2), then builds outwards.

- The diagram of the atom showing the electron arrangement is called a Bohr diagram (Neils Bohr).

- When energy is added to the atom (eg. heat), the electrons absorb some of this energy and become

excited and may jump to a higher energy level.

- When the electron returns to its normal energy level, the extra energy is released in the form of light.

- Different elements require different amounts of energy to move the electrons.

- The number of electrons and protons are usually balanced resulting in neutrally charged matter.

- If an electron is removed from an atom, the atom becomes positively charged (and is called a cation)

(it has lost some of its negative charge).

- If it gains one or more extra electrons, it becomes negatively charged (called an anion).

- An atom with a positive/negative charge is called an ion.

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The Rutherford-Bohr Model of the Atom and Chemical Families

- The Rutherford-Bohr Model is the model of which the electrons are around the nucleus and the

protons and neutrons are in the nucleus.

- Atoms are very small.

- The mass of an electron is extremely small compared to the mass of the entire atom.

- The electrons exist in energy levels outside the nucleus.

- Atoms are made of charged particles that can be separated from each other to form ions.

- The identity of an element is determined by the number of protons in the nucleus.

- Atoms of the same element can differ only in the number of neutrons in the nucleus.

- The periodic table is also organized by atomic number and the number of electrons in their outermost

energy level, called the valence shell electrons.

- Each column represents a group of elements that have similar properties, and they are called families.

- They are in the same family because they have the same number of valence shell electrons and this

determines their chemical properties (what they react with).

- 1st column except for hydrogen is called the Alkali metal Family, which has 1 electron in their

valence shell. They will react with water explosively, and they are shiny &s soft metals.

- The second column (Be, Mg, Ca… ) is called the Alkaline Earth Metal Family. They are very

reactive and only found natruall in compounds.

- The 17th column (group 7… F, Cl, Br….) is called the Halogen Family. Halogen means salt former

and all compounds with halogen elements are salts. They also kill germs when dissolved in water.

- The last column (18th column groupe 8, He,Ne,Ar…) is called the Noble/Nobel Gases family. They

are completely filled (the valence shell) and they will not readily combine with other elements to

form compounds. When electricity is passed through the gases, light is released.

Compounds

- When two or more elements combine together chemically to form a compound, the atoms are held

together by stored energy called bonds.

- When a compound forms, it has very different properties than the original elements.

- Eg. Na + Cl NaCl

- Na (explosive metal) + Cl (Poisonous gas) = salt (tasty food additive)

- There are two types of compounds formed when atoms come together and bond: ionic compounds

and molecular compounds.

- Ions are atoms with a charge.. either they have lost/gained electrons (P.D.M).

- Metals always lose electrons to make their outer energy level become stable

- Eg. Na (atomic number 11) has an electron arrangement of 2,8,1. The sodium atom will give away

it’s one valence electron so that it appears to have a stable outer energy level (8) and the atom ends up

with a charge of +1 (one more proton than electrons). A sodium ion is written as Na+1

or Na+.

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- Eg. Mg with an electron arrangement of 2, 8,2 will lose its two outer electrons and become Mg+2

.

- Non-metals always gain electrons to make their outer energy level stable.

- Eg. Cl (atomic number 17) has an electron arrangement of 2, 8, 7. It will gain 1 electron to produce a

stable outer energy level and the atom ends up with a charge of -1 (one more electron than protons).

A chlorine ion is written as Cl-1

or just Cl-.

- Metal ions are always positive and non-metal ions are always negative. A positive charge on a metal

ion will attract the negative charge on a non-metal ion and the two ions will stick (bond) together,

forming an ionic compound. This attraction is called an ionic bond.

- The charges almost always balance out so an ion with a charge of +1 (Na+) will attract an ion with a

charge of -1 (Cl-) to produce a balanced (stable) ionic compound (NaCl).

-

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- An ion with a charge of +2

can attract an ion with a charge of -2

or two ions with a charge of -1

.

Ca+2

+ 2Cl- →CaCl2

- Whenever a chemical reaction is written, the starting substances (called the reactants) are written

first, followed by an arrow (→), and then the resulting substances (called the products).

Eg. Mg+2

+ O-2

→ MgO

- One method used to find the chemical formula for the product at the end of the reaction is called the

Criss Cross Method: Write the symbol for the elements and then put their charge above each one.

Then forget the signs (+/-) and crisscross the numbers.

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Mg F = MgF2

- This crisscross method also works when forming molecular compounds. Molecular compounds are

formed when two non-metals bond together by sharing one or more pairs of electrons (called

covalent bonds).

- H2 gas, N2 gas, O2 gas, CO2 are diatomic molecules – (since 2 of the same atoms bonded together).

- When writing the name of ionic compounds, the metal element name always comes first and the non-

metal element name is changed to end in “ide”.

- Eg. Na+ + Cl

- → NaCl

- Sodium + Chlorine → Sodium Chloride

- Eg. K+ + N

-3 → K3N

- Potassium + Nitrogen → Potassium nitride