Elements Of Life

Question 1

Describe and explain the difference between the thermal stability of magnesium carbonate compared to calcium carbonate (3)

Answer 1

•Calcium carbonate is more thermally stable than magnesium carbonate (1)
•The calcium and magnesium ions have the same charge, but magnesium ion is smaller so has higher charge density (2)
•So polarises the carbonate ion more, meaning less energy is required to break the carbonate apart (3)

Question 2

What happens to ionisation enthalpy across a period? Why is this?

Answer 2

It increases; more protons in the nucleus so greater forces of attraction from positive nucleus pulling in negative valence electrons and no more shells so no more shielding or distance from the nucleus, so more energy required to remove an electron

Question 3

What happens to ionisation enthalpy down a group? Why is this?

Answer 3

It decreases; more protons in the nucleus so greater forces of attraction between positive nucleus pulling in negative valence electrons, but more shells are added going down the group so more shielding and greater distance from the nucleus so weaker electrostatic forces of attraction overall meaning less energy is required to remove an electron

Question 4

Why are metals able to conduct electricity?

Answer 4

Delocalised sea of electrons; electrons are mobile and can move freely so can carry electric charge

Question 5

When drawing an ionic lattice, which ion is larger? Why?

Answer 5

Negative ion; it has gained a full outer shell

Question 6

What is the shape of a s-orbital?

Answer 6

Spherical

Question 7

What is the shape of a p-orbital?

Answer 7

‘Dumbell’ shaped

Question 8

Give the flame tests for:
Lithium
Sodium
Potassium
Calcium
Barium
Copper

Answer 8

Li -> Red
Na -> Yellow
K -> Lilac
Ca -> Red
Ba -> Green
Copper -> Blueish-green

Question 9

How can you form an anhydrous salt from a hydrous salt?

Answer 9

Heat until constant mass

Question 10

During nuclear fission, what two species fuse?

Answer 10

Nuclei (NOT ATOMS!)

Question 11

What subatomic particle did JJ Thompson discover?

Answer 11

The electron

Question 12

What subatomic particle did James Chadwick discover?

Answer 12

The neutron

Question 13

What is the trend (down the group) of alkalinity in the group 2 hydroxides?

Answer 13

Get more alkaline down the group; they are more soluble going down

Question 14

State and explain the bond angle around ammonia (NH3) (5)

Answer 14

•107° (1)
• Sets of electrons repel (2)
• .. so go as far apart as possible (3)
• Central nitrogen atoms has 4 sets of electrons (4) (3 bonding pairs and 1 lone pair)
• Lone pairs repel more than bonding pairs so pushes the bond angle closer together (5)

Question 15

List all the 3d shapes of molecules that can occur AND state the bond angle(s)

Answer 15

• Linear (Diatomic elements or two sets of bonding electrons with no lone pairs), 180°
• Bent (Two bonding sets of electrons with one lone pair)
• Trigonal planar (Three sets of bonding electrons with no lone pairs), 120°
• Trigonal pyramidal (Three sets of bonding electrons with one lone pair)
• Tetrahedral (Four sets of bonding electrons with no lone pair), 109.5°
• Trigonal bipyramidal (Five sets of bonding electrons with no lone pair), 90° and 120°
• Octahedral (Six sets of bonding electrons with no lone pair), 90°