CHEMICAL BONDING CHEMISTRY

1a) What is a compound?

A compound is made up of two or more different elements chemically combined

1b) Define the octet rule?

When bonding, most atoms tend to reach an electron arrangement of eight electrons in their outer energy level

1c) What is meant by the term valency?

The valency of an element is the number of atoms of hydrogen with which an atom of the element can bond

1d) Give the valency of the elements in each group of the periodic table

Group 1: 1, Group 2: 2, Group 3: 3, Group 4: 4, Group 5: 3, Group 6: 2, Group 7: 1, Group 8: 0

2i) Sulfate

SO₄²⁻

2ii) Nitrate

NO₃⁻

2iii) Carbonate

CO₃²⁻

2iv) Nitrite

NO₂⁻

2v) Sulfite

SO₃²⁻

2vi) Hydroxide

OH⁻

2vii) Phosphate

PO₄³⁻

2viii) Hydrogencarbonate

HCO₃⁻

3i) Sodium bromide

NaBr

3ii) Calcium sulfide

CaS

3iii) Potassium oxide

K₂O

3iv) Magnesium fluoride

MgF₂

3v) Aluminium sulfide

Al₂S₃

3vi) Beryllium hydride

BeH₂

3vii) Lithium sulfate

Li₂SO₄

3viii) Magnesium nitrate

Mg(NO₃)₂

3ix) Silver (I) sulfide

Ag₂S

3x) Calcium hydroxide

Ca(OH)₂

3xi) Sodium phosphate

Na₃PO₄

3xii) Beryllium sulfite

BeSO₃

3xiii) Aluminium carbonate

Al₂(CO₃)₃

3xiv) Sodium hydrogencarbonate

NaHCO₃

3xv) Copper (II) bromide

CuBr₂

3xvi) Chromium (III) oxide

Cr₂O₃

3xvii) Calcium phosphate

Ca₃(PO₄)₂

4i) Ammonia

NH₃

4ii) Methane

CH₄

4iii) Water

H₂O

4iv) Hydrogen peroxide

H₂O₂

4v) Phosphine

PH₃

4vi) Carbon monoxide

CO

4vii) Carbon dioxide

CO₂

4viii) Sulfur dioxide

SO₂

4ix) Sulfur trioxide

SO₃

4x) Nitrogen monoxide

NO

4xi) Nitrogen dioxide

NO₂

4xii) Oxygen difluoride

OF₂

4xiii) Boron trichloride

BCl₃

5) Name the two types of chemical bonding

1) Ionic Bonding, 2) Covalent Bonding

6a) What is an ionic bond?

An ionic bond is the electrostatic attraction between a positive and negative ion

6b) Using Lewis diagrams, show how an ionic bond is formed

Formed by transfer of electrons from metal to non-metal, resulting in oppositely charged ions that attract

6c) Describe the structure of ionic compounds

Ionic compounds form a crystal lattice structure; each positive ion is surrounded by six negative ions and each negative ion is surrounded by six positive ions

6di) Melting and boiling points of ionic compounds

Very high melting and boiling points – the electrostatic attractions between the oppositely charged ions are very strong and require a lot of energy to be broken

6dii) Appearance of ionic compounds at room temperature

Exist as solid crystalline structures (crystal lattice structures)

6diii) Conductivity of ionic compounds

Do not conduct electricity in the solid state as the ions are not free to move; conduct electricity ONLY when molten or dissolved in water as ions are free to move

6e) Give three uses of ionic compounds

1. Different salts are used on food to act as a preservative, 2. Sodium chloride salt is spread on roads in winter to help melt ice and snow, 3. Hydrated sodium carbonate used in washing soda tablets to clean clothes and remove hardness from water

7) Describe an experiment to test for Chloride ions

Dissolve salt in water, add silver nitrate solution; white precipitate forms (AgCl), which dissolves in dilute ammonia

7) Describe an experiment to test for Sulfate and sulfite ions

Dissolve salt in water, add barium chloride solution; white precipitate forms (BaSO₄ or BaSO₃). Add dilute HCl; sulfate precipitate remains, sulfite precipitate dissolves

7) Describe an experiment to test for Carbonate and hydrogencarbonate ions

Dissolve salt in water, add dilute HCl; fizzing/effervescence (CO₂ gas) turns limewater milky. To distinguish: Add magnesium sulfate solution; carbonate forms white precipitate (MgCO₃), hydrogencarbonate does not

7) Describe an experiment to test for Nitrate ions

The Brown Ring Test: Dissolve salt in water, add freshly prepared iron(II) sulfate solution, slant tube and carefully add concentrated sulfuric acid down the side; a brown ring forms at the junction

7) Describe an experiment to test for Phosphate ions

Dissolve salt in water, add ammonium molybdate solution and concentrated nitric acid, place in warm water bath; a yellow precipitate forms

8a) What is a covalent bond?

A covalent bond is the type of bond that forms when two atoms share a pair of electrons

8b) What is a molecule?

A molecule is made of two or more atoms chemically combined

8c) Use Lewis diagrams show how a covalent bond is formed

Formed by the overlap of orbitals (sharing of electrons) between non-metal atoms to achieve stable electron configurations

9a) Outline the valance shell electron pair repulsion theory

The shape of a molecule depends on the number and type (bond pairs or lone pairs) of electron pairs around the central atom; electron pairs repel each other and try to be as far apart as possible

9bi) Shape and bond angle for two bond pairs

Linear shape, 180˚

9bii) Shape and bond angle for three bond pairs

Trigonal Planar shape, 120˚

9biii) Shape and bond angle for four bond pairs

Tetrahedral shape, 109.5˚

9biv) Shape and bond angle for three bond pairs and one lone pair

Pyramidal shape, 107˚

9bv) Shape and bond angle for two bond pairs and two lone pairs

V- shaped/ bent, 104.5˚

10a) What is a sigma bond?

A sigma bond is a bond formed by the HEAD ON overlap of two orbitals

10b) What is a pi bond?

A pi bond is a bond formed by the SIDEWAYS overlap of p or d orbitals

10c) What type of bond is a single covalent bond?

A single covalent bond is a sigma bond

10d) What type(s) of bond is a double covalent bond?

A double covalent bond has one sigma bond and one pi bond

10e) What type(s) of bond is a triple covalent bond?

A triple covalent bond has one sigma bond and two pi bonds

10f) Give two differences between sigma and pi bonds

Sigma bonds are formed by head-on overlap and are stronger; Pi bonds are formed by sideways overlap and are weaker

10gi) Sigma and pi bonds in Chlorine gas (Cl₂)

1 sigma bond, 0 pi bonds

10gii) Sigma and pi bonds in Oxygen gas (O₂)

1 sigma bond, 1 pi bond

10giii) Sigma and pi bonds in Nitrogen gas (N₂)

1 sigma bond, 2 pi bonds

11i) Melting and boiling points of covalent compounds

Low melting and boiling points – there are intermolecular forces between covalent molecules which are generally weak and easily broken

11ii) Appearance of covalent compounds at room temperature

Can be gases, liquids, or solids

11iii) Conductivity of covalent compounds

Do not conduct electricity as they have no free ions or electrons