4.1 Ionic Bonding And Structure

Question 1

Ionic bond

Answer 1

Electrostatic attraction between oppositely charged ions

Question 2

What type of elements can an ionic bond be formed between?

Answer 2

Elements with electronegativity difference of 1.8 or greater

Question 3

Where are the electrons transferred from?

Answer 3

The transfer is from one or more electrons from the valence shell of one atom to the other’s valence shell

Question 4

Octet rule

Answer 4

Atoms are more stable with electron configuration of a noble gas

Question 5

Why is ammonium chloride an exception to the usual metal-non metal ionic bond?

Answer 5

NH4Cl is an exception because it has both ionic bonding between ions and covalent bonding between atoms

Question 6

Lattice structure

Answer 6

Regular crystalline arrangement made of alternating cations and anions. Ratio is 1:1

Question 7

What does “ionic bonding is non-directional” mean?

Answer 7

It means the force of attraction occurs in all directions around ions

Question 8

Are all ionic compounds molecules?

Answer 8

No. Eg. NaCl is always referred to as a compound not a molecule

Question 9

Polyatomic ions and bonding

Answer 9

Those that consist of more than one type of atom. Usually their atoms are bonded by covalent bonds but between them and another ion is an ionic bond

Question 10

Formula for hydroxide, carbonate and ammonium ions

Answer 10

OH-
HCO3-
NH4+

Question 11

Ion formulae for nitrate and nitrite

Answer 11

Nitrate: NO3-
Nitrite: NO2-

Question 12

Ion formulae for chlorate, perchlorate, chlorite and hyperchlorite

Answer 12

Chlorate: ClO3-
Perchlorate: ClO4-
Chlorite: ClO2-
Hyperchlorite: ClO-

Question 13

Ion formulae for sulfate, sulfite and phosphate

Answer 13

Sulfate: SO4 2-
Sulfite: SO3 2-
Phosphate: PO4 3-

Question 14

How many ions does Fe2(SO4)3 have?

Answer 14

5 ions

Question 15

Why do compounds with ionic bonds have high melting and boiling points?

Answer 15

As the attraction/ bond between ions is very strong, large amounts of energy are required to overcome them. Hence the MP and BP is high and they are usually solids under STP

Question 16

In Na2O and MgO, which will have higher melting point and why?

Answer 16

MgO will have higher melting point as the greater the charge and the smaller its atomic radius, the higher attraction will be.

Question 17

Volatility

Answer 17

How easily a substance evaporates

Question 18

Why do ionic compounds have low volatility?

Answer 18

As they require a lot of energy to overcome strong forces of attraction, they don’t evaporate so easily hence low volatility

Question 19

What are the 2 steps in solubility?

Answer 19

1. Dissolves: Breaks down lattice structure

2. Hydrates: Separated ions get surrounded by water molecules

Question 20

What does solubility depend on?

Answer 20

The forces of attraction between water and ions

Question 21

Why are water molecules polar?

Answer 21

Because of difference in electronegativity in H+ and O2-. This leads to partial opposite charges

Question 22

How does polarity help water as a solvent?

Answer 22

Partial charges of water are attracted to opposite charges of ions and allows water to separate compounds

Question 23

Why are hexane and propane limited solvents?

Answer 23

They are non-polar and so they have difficulty in disrupting lattice structure

Question 24

What does electrical conductivity depend on?

Answer 24

The presence of mobile ions

Question 25

Why can’t ionic compounds conduct electricity as solids?

Answer 25

The ions are held in fixed positions and hence immobile

Question 26

When do ionic compounds conduct electricity and why?

Answer 26

When they are molten or dissolved as ions are free to move and can carry current

Question 27

What does it mean when we say “ionic compounds are brittle”?

Answer 27

It means they tend to shatter when force is applied

Question 28

Why are ionic compounds brittle?

Answer 28

When force is applied, layers become aligned incorrectly and repulsion between “like” ions causes it to split and fracture