Bonding

Question 1

What is metallic bonding?

Answer 1

The attraction between layers of positive and a sea of delocalised electrons. It is described as a metallic lattice.

Question 2

What is a lattice?

Answer 2

Regular arrange of atoms or ions.

Question 3

Describe the 4 physical properties of metals.

Answer 3

1) Hardness - Strong attraction between positive ions and negative electrons in a regular structure
2) High melting point - Large amounts of energy required to break the bonds
3) Good electrical conductivity - Delocalised electrons can move and carry charge throughout the metal
4) Malleability and ductility - Layers of positive ions can slide over each other without disrupting the structure

Question 4

Why does Mg have a higher melting point than Na?

Answer 4

Mg can delocalise 2 electrons per atom while Na can only delocalise one per atom. The more electrons that are delocalised the stronger the metallic bond.

Question 5

Describe ionic bonding

Answer 5

The electrostatic attraction between oppositely charged ions in a regular lattice. Ionic lattice.

Question 6

What is ionic bonding generally between?

Answer 6

A metal and a non-metal.

Question 7

What are positive ions and negative ions called

Answer 7

Positive - Cation

Negative - Anion

Question 8

What are the physical properties on ionic compounds?

Answer 8

1) Crystalline - Regular lattice of positive and negative ions
2) High m.p and b.p - A large amount of energy is required to break the strong electrostatic attractions between the ions of opposite charge.
3) Non conductor when solid - Ions are not free and cannot cary charge
4) Good conductor when molten - Ions are free to move and carry charge

Question 9

Whats special about sodium chloride?

Answer 9

It has a 6:6 crystal arrangement. 6 Na surround 1 Cl and 6 Cl surround 1 Na.

Question 10

What affects the melting point of an ionic compound?

Answer 10

The smaller the ion and the higher their charge the stronger their ionic bond.

Question 11

What is a covalent bond?

Answer 11

The electrostatic attraction between a shared pair of electrons and the nuclei of bonded atoms.

Question 12

What do covalent bonds exist between? Are there any exceptions?

Answer 12

Non metal atoms, BeCl2 and AlCl3 are two exceptions because both Be and Al are metals.

Question 13

What is the octet rule?

Answer 13

When reacting, an atom tends to gain, lose or share electrons to achieve eight in its outer shell

Question 14

What is a coordinate bond? How do you draw it?

Answer 14

When one atom contributes both of the shared pair of electrons e.g. NH4+ .
You draw it with an arrow towards the atom in the coordinate bond.

Question 15

What is a polar bond?

Answer 15

A covalent bond in which there is unequal sharing of the bonding electrons

Question 16

Describe electronegativity

Answer 16

The extent to which an atom attracts the bonding electrons in a covalent bond

Question 17

What trends are there in electronegativity?

Answer 17

Decreases down the group - Bonding electrons further from the attractive power of the nucleus
Increases across the period - Bonding electrons closer to attractive power of the nucleus.

Question 18

What does very small, small and large difference in electronegativity give ?

Answer 18

No/ v.small - This gives a non-polar molecule
Small - Gives a polar molecule
Large - Ionic compound.

Question 19

What happens if a polar molecule is symmetrical?

Answer 19

The bond polarities cancel eachother out and the molecule has no overall dipole.