Unit 1 AOS1 Chapter 4.2 Structure and properties of ionic substances

Question 1

What is ionic bonding between?

Answer 1

Ionic bonding is the bonding between a metal and a non-metal

Question 2

What are ionic compounds?

Answer 2

Ionic compounds are compounds that exhibit ionic bonding

Question 3

Why can metals reat with non-metals?

Answer 3

Metals can react with non-metal because the electrons lost by the metals can be taken up by the more electronegative non-metals. This transfer results in an ionic bond between metal cations and non-metal anions.

Question 4

What is a salt?

Answer 4

Salt is a ionic compound consisting of a metal ion and non-metal ion.

Question 5

What do ionic compounds form?

Answer 5

Ionic compounds form crystals that are composed of three-dimensional arrays of positive metal ions and negative non-metal ions.

Question 6

What are ionic bonds?

Answer 6

Ions in an ionic lattice are held together by strong electrostatic forces of attraction between oppositely charged ions also known as ionic bonds.

Question 7

How are ions a crystal packed?

Answer 7

They pack together in the way that will achieve the most stable arrangement, with oppositely charged ions as close together as possible, and similarly charged ions as far apart as possible. Each cation is thus surrounded by anions and each anion by cations.

Question 8

What determines the actual lattice structure?

Answer 8

The relative sizes and numbers of the ions present determine the actual lattice structure.

Question 9

What is required for a substance to conduct electricity?

Answer 9

For a substance to conduct electricity it must have charged particles that are free to move.

Question 10

What is an electrolyte?

Answer 10

Electrolyte is a conducting solution.

Question 11

Ionic compounds cannot conduct electricity in solid state in what two ways can they conduct electricity?

Answer 11

They can be molten (melted), which means that the ions they are made from can move freely in the now liquid state. A second way is through dissociation. This is where the substance dissolves in water and the ions from the lattice are pulled apart by the water molecules and are able to move freely through the solution. This free movement of ions in water forms a conducting solution called an electrolyte.

Question 12

Explain why ionic substances can conduct electricity when in liquid state but not in solid state?

Answer 12

For a substance to conduct electricity there must be mobile charged particles within the substance. In a solid salt , there are charged particles but they are stationary thus they cannot conduct electricity however in a molten salt or a salt dissolved in water the cations and anions are mobile and thus can conduct electricity.

Question 13

Why are ionic compounds hard?

Answer 13

Ionic compounds are hard because the ionic bonding between the cations and anions is very strong and thus a high amount of energy is required to displace the cations and anions from their original positions.

Question 14

Why do ionic compounds have high melting and boiling points?

Answer 14

Ionic compounds have high melting and boiling points because the ionic bonding between the cations and anions is very strong so a high amount of energy is required to separate them from one another when melting or boiling a substance.

Question 15

Why can some ionic substances dissolve in water?

Answer 15

Some ionic substances can dissolve in water because H2O molecules are able to move between ions and free them up disrupting the rigid crystal structure.

Question 16

Why are ionic compounds brittle?

Answer 16

Ionic compounds are brittle because if a force caused movement of a layer of ions in an ionic lattice , they would no longer be aligned with adjacent opposite charges causing the like ions to repel and break the lattice.

Question 17

Why can some ionic compounds not dissolve in water?

Answer 17

Some ionic compounds do not dissolve in water because some ionic compounds have a large difference in charge which means there is a stronger force of attraction between the ions than the water molecules , thus dissociation cannot occur and thus they are insoluble.

Question 18

What influences the melting point of a ionic compound.

Answer 18

The higher the electrostatic attraction between the ions the higher the mp.

Question 19

What can produce a higher electrostatic attraction force?

Answer 19

A higher electrostatic attraction can be produced by higher charges or shorter distances between the charged particles.

Question 20

What increases the conductivity of a dissolved ionic compound.

Answer 20

The greater number of ions the greater the conductivity.

Question 21

Magnesium chloride, MgCl2, and potassium chloride, KCl, are typical ionic compounds.
a. Describe how their ionic lattice structure is formed from their respective atoms.
b. Show why their empirical formulas have ratios of 1 : 2 and 1 : 1 respectively.

Answer 21

a)The ions Mg2+ and 2Cl− make up MgCl2.
The ions K+ and Cl− make up KCl.

b)MgCl2 has the ratio 1 : 2 because two Cl− ions are needed to balance the one Mg2+ ion. KCl has the ratio of 1 : 1 because one K+ ion balances one Cl− ion.

Question 22

Explain, by referring to the ionic and metallic bonding models, why ionic substances are brittle but metals are malleable?

Answer 22

An ionic lattice must maintain an alternating positive and negative ion arrangement; therefore, movement of layers cannot happen without repulsion breaking the lattice.
Metal lattices have the same charges throughout the lattice, allowing for flexibility.