Write down the formulae for these:

a) Iron (II) Sulfateb) Magnesium Oxidec) Silver Carbonated) Sodium Phosphatee) Copper Hydroxidef) Aluminium Hydroxideg) Barium Nitrate

1. Which of these are “cations”?

2. Which of these are “anions”?

3. Which of these are “polyatomic ions”?

Chloride Cl- Sulfate SO4

2-

Zinc Zn2+ Sodium Na+

Carbonate CO32- Hydroxide OH-

Hydrogen H+ Nitrate NO3-

Oxide O2- Calcium Ca2+

Write down the formulae for these ionic compounds

a) Potassium Chlorideb) Magnesium Carbonatec) Magnesium Chlorided) Sodium Carbonatee) Magnesium Hydroxidef) Magnesium Nitrate

1. Write down the electron configuration of a chlorine atom

2. Write down the electron configuration of a chloride ion

3. Write down the symbol and charge of the chloride ion

4. Describe HOW ions are formed

5. Describe WHY ions are formed

6. Describe the difference between atoms and ions

Question ONEa) atoms of same number of protons but

different number of neutronsb) number of protonsc) number of protons + neutronsd) protons, electrons, neutrons

Question TWOe) Sodium = 2, 8, 1f) Oxygen = 2, 6g) Calcium = 2, 8, 8, 2h) Si (silicon) = 2, 8, 4i) Ar (argon) = 2, 8, 8

Question FOURIons have charge, but atoms don’t. Atoms are neutral (#protons = #electrons), but ions have charge because they have unequal number of protons and electrons after losing/gaining electrons.

Question FIVEIons are formed when atoms lose or gain electrons, in order to obtain full outer shell.

IonsAn ion is an atom or a group of atoms that has gained or lost one or more electrons.

Atoms always want to have outer shells that are complete (full), giving it stable electron structure.

Atoms which gain electrons become ________ charged – called “anions”

Atoms which lose electrons become ________ charged – called “cations”

Ion formation - Example1. What is the electron configuration

(arrangement) of a sulfur atom?

2. Will it lose or gain electron(s)?

3. How many?

4. Protons (+) vs. Electrons (-)

5. Cation or anion?

6. What is the new electron configuration?

Li F

Neutral Atoms

Atomic # : Atomic # :

# or electrons in a neutral atom :

# or electrons in a neutral atom :

3

3

9

9

Li F

Ions

Cation

Li+

AnionF-

Be O

Ions

Cation

Be2+

AnionO2-

Cations (positively charged ions)• Hydrogen H+

• Lithium Li+

• Sodium Na+

• Calcium Ca2+

• Magnesium Mg2+

• Zinc Zn2+

• Aluminium Al3+

Anions (negatively charged ions)• Chloride Cl-

• Oxide O2-

• Sulfide S2-

• Hydroxide OH-

• Nitrate NO3-

• Sulfate SO42-

• Carbonate CO32-

Hydrogen H+

Lithium Li+

Sodium Na+

Calcium Ca2+

Magnesium Mg2+

Zinc Zn2+

Aluminium Al3+

Iron II Fe2+

Iron III Fe3+

Chloride Cl-

Oxide O2-

Sulfide S2-

Hydroxide OH-

Nitrate NO3-

Sulfate SO42-

Carbonate CO32-

Practical – producing “iron sulfide”

1. Give names of any three cations

2. Give names of any three anions

3. What is the difference between an atom and an ion?

Writing formulae for ionic compounds

1. Look at the charges of the ions you are putting together.

2. If “positive charge = negative charge”, then just put their formulae together (easy!) Example: Mg2+ + CO3

2- → MgCO3

3. Remember – there is no need to write down the charges (the little numbers on the top with plus and minus) on the final answer

How to write down the formulae for ionic compounds

4. But what about putting these two together? Na+ and CO3

2- The charges are unbalanced here. To make it balanced, you need TWO sodium ions (Na+). 2Na+ + CO3

2- → Na2CO3

5. What about these two? Ca2+ and Cl-

Ca2+ + 2Cl- → CaCl2

6. Be careful when you deal with polyatomic ions (e.g. NO3

-). You have to put brackets around them if you have more than one.

For example:

Ca2+ + 2OH- → Ca(OH)2

Ca2+ + 2NO3- → Ca(NO3)2

7. Can you work out this one?

Al3+ + CO32- → __________

Try these…

1. Sodium chloride2. Sodium hydroxide3. Sodium nitrate4. Magnesium Oxide5. Magnesium sulfate6. Magnesium carbonate7. Calcium carbonate

Now try these…

1. Sodium carbonate2. Lithium carbonate3. Potassium sulfate4. Sodium phosphate5. Magnesium chloride6. Calcium chloride7. Aluminium chloride

Are you ready for these?

1. Calcium hydroxide2. Magnesium hydroxide3. Magnesium nitrate4. Zinc nitrate5. Aluminium hydroxide6. Aluminium nitrate7. Aluminium carbonate

Chemical Formulae A molecule of glucose contains what

elements? In what proportions?

C6H12O6

Carbon, Hydrogen and OxygenTwice as many Hydrogen as Carbons and

Oxygens.

Sucrose is two glucose molecules bonded together. What is its chemical formula?

Ionic Compounds

sodium chlorine

Use Lewis dot diagramsNa Cl

1+1-

Ionic Compounds

sodium chlorine

sodium chlorideNaCl

Cl1+

1-

Na

Ionic Compounds How do we write the Formula?

Reactant + Reactant Product

Na+ + Cl- NaCl

Ionic Compoundslithium oxygen

Li

O

Li

1+

1-1+

2-

Ionic Compoundslithium oxygen

Lithium oxide Li2O O

Li

1+

2-1+

Li

Ionic Compounds How do we write the Formula?

Reactant + Reactant Product

Li+ + O2- Li2O2

O

O

Try This !aluminum oxygen

aluminum oxideAl2O3

Al

Al

O

Ionic Compounds How do we write the Formula?

Reactant + Reactant Product

Al3+ + O2- Al2O32 3