Ionic Equations, Solubility, Etc

Question 1

How do metal atoms get a noble gas configuration?

Answer 1

They lose the few electrons in their outer shell and become positive ions

Question 2

What happens to the donated electrons during metallic bonding?

Answer 2

They form a sea of delocalised electrons surrounding the lattice of positive ions

Question 3

What is metallic bonding?

Answer 3

The very strong electrostatic attraction between the positive ions in the lattice and the negative sea of delocalised electrons

Question 4

What are the two typical properties of metals (from the spec) and why do they have these properties?

Answer 4

1. High melting and boiling point - metallic bonding is very strong
   —> group 2 metals have a higher m/b.p than corresponding g1 metals because each g2 atom has 2 electrons to donate to the sea, so there’s more delocalised electrons meaning the electrostatic attractions are stronger.
2. Conduct electricity - delocalised electrons are mobile so when a voltage is applied, they all move in the same direction (towards the positive terminal)
   (The flow of charged particles is the electric current)

Question 5

Why are g2 metals harder and more dense (than g1)?

Answer 5

More energy is required to overcome their stronger (relative to g1) electrostatic attractions

Question 6

What’s the difference between bonding and structure?

Answer 6

Bonding: how atoms are held together (ionic, covalent or metallic)
Structure: giant or molecular (simple)

Question 7

If the bonding is ionic or metallic, what will the structure be?

Answer 7

Giant

Question 8

If the bonding is covalent, what will the structure be?

Answer 8

Could be giant (covalent network) or molecular (simple covalent molecules)

Question 9

How do you tell if a substance is a simple or giant structure?

Answer 9

All giant structures have a high mp. If something is a gas or liquid at room temp it will be a simple structure and hence have covalent bonding between the atoms in the molecule (or be a noble gas)

Question 10

What types of substances can the words ‘molecular’ ‘ intermolecular’ or ‘molecule’ be used for?

Answer 10

Covalent substances (because molecules are always covalently bonded)

Question 11

What do you need to consider when comparing the melting points of substances?

Answer 11

• type of bonding & structure
• what forces/attraction/bonds are actually breaking?
• how strong are they?
• how much energy is needed to overcome them?

Question 12

Why does nitrogen dioxide have a lower melting point than silicon?

Answer 12

Nitrogen dioxide is a simple molecule so intermolecular forces need to be overcome to melt it
Silicon is a giant covalent network structure so covalent bonds must be broken in order for it to melt
The covalent bonds are stronger than the intermolecular forces so require more energy to break them

Question 13

Does magnesium or sodium have a higher melting point (& why)?

Answer 13

Both have metallic bonding, but in magnesium, there’s a greater number of delocalised electrons and the cations are more highly charged (Mg2+) than in Sodium (Na+)
This means there are stronger electrostatic attractions between the cations and delocalised electrons
This means it takes more energy to overcome the attractions in Mg compared to Na

Question 14

What are cations?

Answer 14

Positive ions

Question 15

What are anions?

Answer 15

Negative ions

Question 16

How are ionic compounds held together?

Answer 16

Strong electrostatic attractions that form a giant ionic lattice

Question 17

What is ionic bonding?

Answer 17

The overall attraction between the positive and negative ions outweighing the repulsion’s and therefore holding the ions together in a lattice structure

Question 18

What must you do to get all the marks when drawing an ionic lattice?

Answer 18

• make sure the positive and negative ions are alternating along each row and column
• draw the positive ions smaller than the negative ones (because the same number of protons are now attracting fewer electrons, so are held together more tightly)
• say there are further layers above and below (ie it is a 3D structure)
• note that (for example) in a sodium chloride lattice, each sodium ion is surrounded by 6 chloride ions as nearest neighbours and vice versa (in front, behind, above, below, left, right)

Question 19

What are 3 typical physical properties of ionic compounds?

Answer 19

1. Solids at room temperature with a high melting point (due to the very strong electrostatic attractions between opposite ions)
2. Most ionic compounds dissolve well in water (as the charged ions can form strong attractions with water molecules)
3. Can conduct electricity when molten or in solution because the ions (NOT electrons) are free to move, they don’t conduct when solid because the ions are not then free to move, but are held in a lattice position

Question 20

What is the difference between how ions made of more than one element bond to other ions and within the ion itself?

Answer 20

Within the ion, the bonds are covalent, but they bond to other ions with ionic bonding

Question 21

What 2 factors affect the melting points of ionic compounds?

Answer 21

• the charge - the highest charges on both ions
• the size of the atoms - smaller size = stronger ionic bonding