Topic 1: Atomic Structure + Periodic Table

Question 1

What is meant by ‘Atomic number’

Answer 1

Tells us the number of protons in an atom

Question 2

What is meant by ‘mass number’

Answer 2

Tells us the number of protons and neutrons in the nucleus

Question 3

What is an isotope?

Answer 3

Elements with the same number of protons and electrons, but different numbers of neutrons.

Question 4

What is an ion?

Answer 4

An atom which has either gained or lost electrons, to become charged

Question 5

Define ‘Relative atomic mass’

Answer 5

The weighted mean mass of an element, relative to 1/12 the mass of a carbon 12 atom

Question 6

Define ‘Relative isotopic mass’

Answer 6

The mass of an atom of an isotope compared to 1/12 the mass of a carbon 12 atom

Question 7

Define ‘Relative molecular mass’

Answer 7

The mean mass of a molecules, compared to 1/12 the mass of a carbon 12 atom

Question 8

How to calculate Relative atomic mass

Answer 8

(Abundance of A x m/z) x
(Abundance of B x m/z)
————————————-
Total Abundance

Question 9

Define ‘First ionization energy’

Answer 9

The energy required to remove one electron from each atom in one mole of gaseous atoms, forming one mole of gaseous 1+ ions

Question 10

Explain the trend in ionization energy along a period

Answer 10

Ionization energy increases along a period.
Shielding is similar
This is because the proton number increases.
So nuclear charge increases
Pulling outer electron in closer to the nucleus
So more energy is required to remove it

Question 11

Explain why there is a difference in ionization energy between groups 2 - 3

Answer 11

Ionization energy is less for G3. This is because the outermost electron is in a higher energy subshell - further from the nucleus.
Therefore more shielding, less attraction to nucleus, and lower ionization energy

Question 12

Explain why there is a difference in ionization energy between groups 5 - 6

Answer 12

Ionization energy is less for G6. This is because the outer electrons in the P orbital (of group 6) have a pair. The pair experience opposite spin, and repulsion, meaning less energy is required to remove an electron

Question 13

Explain why ionization energy decreases down a group

Answer 13

The atomic radius increases as we go down the group
–> So outer electrons are further from the nucleus
Shielding increases as we go down the group
–> So more shells between the nucleus and outer shell
The attractive force between the nucleus and outer shell is weaker, so less energy is required to remove the outer electron

Question 14

Successive ionization energy

Answer 14

The removal of more than 1 electron from the same atom

Question 15

Explain the trend in Atomic radius along a period

Answer 15

Decreases along the period
Electrons go into the same shell - so similar shielding effect
Proton number increases by 1, nuclear charge increases
-> Pulls outer shell towards nucleus

Question 16

Explain the trend in Atomic radius down a group

Answer 16

Increases down the group
Due to additional electron shells added.

Question 17

Trend in melting points: Group 1 - 3

Answer 17

Melting point increases from Groups 1- 3. Metal ions have an increasing positive charge.
Increasing number of delocalised electrons.
Smaller ionic radius
Therefore a stronger metallic bond + higher melting point to overcome this

Question 18

Trend in melting points: Group 4

Answer 18

Has the highest melting point - due to the giant covalent structure.
Many strong covalent bonds hold the atoms together.
Therefore a large amount of energy is needed to overcome this.

Question 19

Trend in melting points: Group 4 - 5 - 6

Answer 19

Large decrease from groups 4 - 5. Group 5 elements have a simple covalent molecular structure. With weak London forces which require little energy to overcome.
Slight increase from groups 5 - 6. Group 6 elements still have a simple molecular structure, yet have more electrons, so have larger London forces.

Question 20

Trend in melting points: Group 6 - 7 - 8

Answer 20

Decrease from group 6 - 7. Due to the smaller simple covalent molecular structure and therefore smaller London forces.
Group 8 has the lowest melting point, as it exists as a single atom, so has very small London forces.

Question 21

Define an orbital

Answer 21

a region within an atom that can hold up to two electrons with opposite spins