1.2 IONSUNDERSTANDING HOW THE ELECTRONS MOVE INSIDE AN ATOM ALLOWS SCIENTISTS TO CONTROL HOW ATOMS REACT WITH EACH OTHER.

VOCABULARY PREVIEW

Look up the following terms an provide a definition that you understand.

Anion

Cation

Ion

Ionic bond

Ionic compound

solubility

A negatively charged ion

A positively charged ion

An atom which has either gained or lost an electron

An attraction between two oppositely charged ions

When anions and cations come together (sodium chloride)

How easily something dissolves

USING VISUALS

Discuss why lithium is likely to form a cation (positive) when it only has one loose electron around it.

Compare this with oxygen or chlorine, which are more likely to gain an electron to complete their shells.

Cl

ATOMS AND IONS

Atoms are electrically neutral (what does this mean?)

If an electron is removed or added, the atom becomes charged and is now called an?

When an electron is removed from an atom, that atom becomes a charged ion.

A positive ion is known as a?

If an electron is added to an atom, that atom becomes a charged ion.

A negatively charged ion is known as a?

ion

They contain an equal number of positive protons and negative electrons.

positively

cation

negatively

anion

CATIONS

A cation is formed when an atom loses electrons.

Do you think the outermost shell would be mostly empty or mostly full?

The atom will usually lose all the electrons in the outermost shell so that only filled shells remain.

Almost all cations come from metal atoms, why is this? Page 14- Top Paragraph

Mostly empty

COMMON CATIONS

An important non-metallic cation comes from hydrogen (H). Hydrogen ions (H+) are formed whenever an acid is dissolved in water.

The symbols used to represent cations are made up of the atomic symbol and the charge of the ion.

For example: Since sodium (Na) loses one electron, the sodium ion has a charge of +1. This is represented by Na+. Magnesium (Mg) atoms lose two electrons and so the magnesium ion is represented as Mg2+

ANIONS

An anion is produced when an atom gains electrons. This will occur if the outermost electron shell of the atom is almost full. In that case, the atom gains additional electrons until the shell is filled, as seen below

ANIONS

The name of a cation is the same as the atom, however anions are named differently. The chemical name for an anion is similar to the name of the atom but ends in –ide.

What would the following atoms be called when they become anions?

Chlorine

Oxygen

Nitrogen

Iodine

Fluorine

Sulfur

Bromine

Chloride

Oxide

Nitride

Iodide

Fluoride

Sulfide

Bromide

IONIC COMPOUNDS

When anions and cations come together they form compounds made up of large crystal lattices. These compounds are known as ionic compounds.

RECAP

What is a

Anion - A negatively charged ion

Cation - A positively charged ion

Ion - An atom which has either gained or lost an electron

Ionic bond - An attraction between two oppositely charged ions

Ionic compound - When anions and cations come together (sodium chloride)

What ions are formed whenever an acid is dissolved in water? Hydrogen ions (H+)

CHEMICAL NAMES AND FORMULAS

Naming ionic compounds is very easy

Simply write the name of the cation followed by the name of the anion

Write the chemical name for the following compounds

1. Ca2+ and O2- = Calcium Oxide

2. Cu+ and Cl- = Copper Chloride

CHEMICAL FORMULAS

Writing chemical formulas is slightly more difficult.

When writing the formula for an ionic compound you must ensure that there is an equal number of positive and negative charges so that the total charge is zero.

Sodium(Na+) chloride (Cl-) the chemical formula us just NaCl

Magnesium (Mg2+) chloride (Cl-) the chemical formula becomes MgCl2

Charge is at the top, number of atoms is on the bottom.

WRITING IONIC FORMULAS

QUESTION TIME

IONIC BONDING

Cations and anions are attracted to each other because they have opposite electrical charges. When they come close to one another they stick together to form an ionic bond.

Ionic bonds holding crystal lattices together are very strong. Therefore, ionic compounds usually:

Are hard

Are brittle

Have high melting points

IONS IN SOLUTION Some ionic compounds are soluble(dissolve) in water, while others are insoluble (do not

dissolve)

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NAMES OF SOME COMMON IONS

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CHARGES OF REPRESENTATIVE ELEMENTS

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Complete the names of the following ions. Ba2+ Al3+ K+

_________ __________ _________

N3 O2 F

_________ __________ _________

P3 S2 Cl

_________ __________ _________

LEARNING CHECK

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Ba2+ Al3+ K+

barium aluminum potassium

N3 O2 F

nitride oxide fluoride

P3 S2 Cl

phosphide sulfide chloride

SOLUTION

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Formula Ions Name cation anion

NaCl Na+ Cl- sodium chloride

K2S K+ S2- potassium sulfide

MgO Mg2+ O2- magnesium oxide

CaI2 Ca2+ I- calcium iodide

Al2O3 Al3+ O2- aluminum oxide

EXAMPLES OF IONIC COMPOUNDS WITH TWO ELEMENTS

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Write the names of the following compounds.

1) CaO ___________

2) KBr ___________

3) Al2O3 ___________

4) MgCl2 ___________

LEARNING CHECK

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Write the names of the following compounds:

1) CaO calcium oxide

2) KBr potassium bromide

3) Al2O3 aluminum oxide

4) MgCl2 magnesium chloride

SOLUTION

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LEARNING CHECK

Write the formulas and names for compounds of the following ions:

Br− S2− N3−

Na+

Al3+

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SOLUTION

Br− S2− N3−

Na+

Al3+

NaBrsodium bromide

Na2S

sodium sulfide

Na3N

sodium nitride

AlBr3

aluminum bromide

Al2S3

aluminum sulfide

AlNaluminum nitride

IONS IN SOLUTION

When ions are in a solution they can move freely through the liquid meaning they can create a flow of electric charge and therefor conduct electricity.

Only liquids that contain ions will allow an electrical current to flow.

Liquids such as oil or kerosene do not contain ions and therefore do not conduct electricity.

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