Chemical Bonding

Question 1

What are noble gases?

Answer 1

Noble gases belong to the only group where elements’ atoms already have complete valence shells. We refer to this stable arrangement of electrons as noble gas configuration.

Question 2

What’s with elements in Group I and III?

Answer 2

Elements in Group I to III tend to lose electrons in order to achieve noble gas configuration, forming positive ions → METALS

Question 3

What’s with elements in Group V to VII

Answer 3

Elements in Group V to VII tend to gain electrons in order to achieve noble gas configuration, forming negative ions → NON-METALS

Question 4

Where does the staircase line start?

Answer 4

Above aluminium, goes down

Question 5

Describe ionic bonding

Answer 5

Ionic bonding is the transfer of electrons from a metallic atom to a non-metallic atom in order to achieve noble gas configuration. Hence, both elements involved achieve a full valence shell.

Question 6

Describe covalent bonding

Answer 6

Covalent bonding is the sharing of electrons between two or more non-metallic atoms
in order to achieve noble gas configuration.

Question 7

Describe the structure, bonding and energy of ionic bonding

Answer 7

S: Giant ionic lattice of positive and negative ions
B: Held together by strong electrostatic forces of attraction
E: High m.p. as a large amount of energy is needed to overcome the strong electrostatic forces between the ions

Question 8

Describe the structure, bonding and energy of covalent bonding

Answer 8

S: Small molecules
B: Loosely held together by weak intermolecular forces of attraction
E: Low m.p. as a small amount of energy is required to overcome the weak intermolecular forces between the molecules.

Question 9

How is the electrical conductivity of GILS and SMS?

Answer 9

GILS have poor electrical conductivity as solids as there are no mobile ions, but are good electrical conductors in liquid/aqueous states.

Simple molecular structures (SMS) have poor electrical conductivity in ALL STATES as there are no mobile ions

Question 10

Are GILS and SMS soluble in water? Name exceptions

Answer 10

GILS are generally soluble in water. Exceptions include SILVER CHLORIDE.

SMS are generally insoluble in water. Exceptions include AMMONIA and CHLORINE

Question 11

How is the strength of electrostatic forces of attraction determined?

Answer 11

Magnitude of charge: The larger the charge (2+ vs. +), the stronger the electrostatic forces.
Physical size of ions: The larger the size, the further apart the ions and the weaker the electrostatic forces.

Question 12

Name one defining factor of the strength of intermolecular forces of attraction, and how it affects m.p. and b.p.

Answer 12

Size of the molecule: The larger the molecule, the greater the intermolecular forces (assuming all other factors remain constant)

If the strength of the forces of attraction are higher, the melting and boiling points are higher.

Question 13

Explain what is formed in metallic bonding.

Answer 13

A metallic lattice structure forms which is a lattice of positive ions in a sea of delocalised electrons.

Question 14

How do we know the number of delocalised valence electrons?

Answer 14

The number of valence electrons delocalised depends on the corresponding group number in the Periodic Table.
→ The more electrons are delocalised, the higher the melting point.

Question 15

What are the five properties of metals?

Answer 15

1. have moderate to high melting points
2. good electrical conductivity whether solid or molten
3. insoluble in water (but can react)
4. malleable and ductile texture
5. shiny, grey (except gold and copper) appearance

Question 16

What is a macromolecule? How is it different from SMS?

Answer 16

Giant molecular structure where every atom is covalently bonded together.
This is unlike simple molecular substances, which have both covalent bonds and intermolecular forces of attraction.

Question 17

Why do macromolecules have high melting point?

Answer 17

Macromolecules have a high melting point as a lot of energy is needed to break the strong covalent bonds.

Question 18

What is the key quality of diamond?

Answer 18

Used in saw blades and drill bits as they are VERY HARD.

Question 19

What are graphite’s properties?

Answer 19

1. Graphite has a soft and slippery texture
2. Graphite has good electrical conductivity

Question 20

Describe the structure of graphite.

Answer 20

Graphite’s carbon atoms only form three bonds each, and the last valence electron is delocalised. → Graphite has layers of carbon atoms covalently bonded in a hexagonal arrangement, where there are weak intermolecular forces of attractions between each layer. For each layer, the carbon atoms are bonded together by strong covalent bonds.