Chapter 4

Question 1

What is an ion

Answer 1

An ion is a charged particle. Ions form from neutral atoms or from groups of atoms by loss or gain of one or more valence electrons

Atoms gain or lose electrons in order to achieve a more stable electron arrangement

Question 2

Generic formation of ion trend in the periodic table

Answer 2

Atoms in groups 1,2 and 13 lose their electrons and become cations

Atoms in groups 15,16 and 17 gain electrons to become anions

Atoms in group 14 generally do not form ions

Question 3

Exceptions to the ion trend

Answer 3

Lead (Group 14) forms Pb+2
Tin (Group 14) forms Sn+4 and Sn+2
Hydrogen can form H- (hydride ion) as well as H+ (hydrogen ion)

Transition metals have variable oxidation states, however silver tends to form Ag+

Question 4

Ionic compounds

Answer 4

Ionization occurs when electros are transferred between atoms (typically from a metal to a non-metal)

The oppositely charged resultant ions are attracted to each other and held together by electrostatic forces (an ionic bond) to form an ionic compound

Question 5

Ionic formulae

Answer 5

Ionic compounds are electrically neutral. Therefore, the charges of the positive and negative ions that make up the compound must be balanced in the lowest common ratio

Question 6

Describe lattice structure

Answer 6

In the solid state. ionic compounds take on a crystalline lattice structure

The geometry of this lattice varies by the compound, however, we can use the coordination number to describe the number of ions that surround a given ion in the lattice

Lattice energy is a measure of strength of attraction of ions within the lattice

Question 7

Describe lattice structure

Answer 7

In the solid state. ionic compounds take on a crystalline lattice structure

The geometry of this lattice varies by the compound, however, we can use the coordination number to describe the number of ions that surround a given ion in the lattice

Lattice energy is a measure of strength of attraction of ions within the lattice

Question 8

Factors which lattice energy depends upon

Answer 8

Magnitude of the charge
- 2+/- ions have a higher lattice energy than 1+/- ions

Distance between the ions - the size of the ion
- smaller ions pack together tighter and so have a stronger bond

Question 9

Describe the structure of ionic compounds

Answer 9

A lattice structure consisting of cations and anions held together by electrostatic force of attraction

Question 10

Melting and boiling point of ionic compounds

Answer 10

Strong electrostatic between ions in the ionic lattice require large amounts of energy to break resulting in high melting and boiling points

Typically solid at room temperature

Melting and boiling points increase with oxidation number

Question 11

What is volatility?

Answer 11

The tendency of a substance to vaporize

Question 12

Solubility of ions

Answer 12

solubility refers to the ease with which a solid becomes dispersed through a liquid to form a solution

Ionic compounds are generally soluble in ionic or polar solvents but not soluble in non-polar solvents. Generally solubility is determined by the degree to which separated solute particles are able to form bonds with the solvent

Question 13

Conductivity of ions

Answer 13

Conductivity indicated the ability compound to conduct electricity based on whether it contains ions that are able to move and carry a charge

Question 14

Brittleness of ions

Answer 14

When a force is applied, repulsive forces cause the lattice to shatter, and hence ionic compounds are brittle

Question 15

Different between ionic and covalent compounds

Answer 15

Ionic:
Reactive metal + reactive non-metal
electronegativity difference > 1.8

Covalent:
two non-metals
electronegative difference < 1.8

Question 16

What is metallic bonding?

Answer 16

The electrostatic force of attraction between a lattice of positive ions and delocalized electrons

Question 17

What factors affect the strength of metallic bonds

Answer 17

The number of delocalized electrons
The charge of the cation
The radius of the cation

Question 18

Conductivity of metals

Answer 18

Presence of mobile electrons cause electrical conductivity of a metal

When a potential difference is applied across the metal sheet, the free mobile electrons in the metallic crystal start moving towards the positive electrode

The electrons coming from the negative electrode simultaneously replace these electrons

Thus, the metallic sheet maintains the flow of electrons from negative electrode to positive electrode. This constitutes electrical conductivity

Question 19

Ductility of metals

Answer 19

Metals can be beaten into sheets (malleability) and drawn into wires (ductility). Metallic bonds are non-directional in nature

The electrons “insulate” the cations from one another, hence the cations can slide past one another when a pressure/force is applied to the metal

Question 20

What are alloys

Answer 20

solid solutions usually containing more than one metal. held together by metallic bonding

Properties of alloy s are distinct from their component elements due to the packing of the cation in the lattice; alloys are often more chemically stable, stronger and more resistant to corrosion

Question 21

What is a covalent bond

Answer 21

the electrostatic attraction between a pair of shared electrons and positively charged nuclei

A group of atoms held together by covalent bonds form a molecule. Atoms can share 1,2 or 3 pairs of electrons in order to achieve a more stable electron configuration

Question 22

What is bond length

Answer 22

Covalent bond characterized by two values; bond length and bond strength

Bond length at which a covalent bond forms minimizes the energy of the system

Question 23

What is bond strength

Answer 23

Provides a measure of the energy required to break a bond

Short bonds are strong bonds, and hence we can use atomic radius to gauge the relative strength of different bonds