Atomic Structure and the Periodic Table

Question 1

what is the relative atomic mass

Answer 1

the average mass of an atom of an element compared to 1/12th of the mass of an atom of carbon-12

Question 2

what is relative isotopic mass

Answer 2

the average mass of an isotope compared with 1/12th of the mass of an atom of carbon-12

Question 3

how do you calculate relative atomic mass

Answer 3

abundance x mass isotope/

100

Question 4

explain why the relative atomic mass of copper is not a whole number (2)

Answer 4

• a sample of copper is a mixture of 2 isotopes in different abundances
• the relative atomic mass is an average mass of these isotopes which isn’t a whole number

Question 5

how do you find the relative molecular mass using a mass spectrometer

Answer 5

• look at the peak with the highest M/z value

and this gives you the Mr of the compound

Question 6

how many electrons can the s orbital hold

Answer 6

2

Question 7

how many electrons can the p orbital hold

Answer 7

6

Question 8

how many electrons can the d orbital hold

Answer 8

10

Question 9

how many electrons can the 1st shell hold

Answer 9

2

Question 10

how many electrons can the 2nd shell hold

Answer 10

8

Question 11

how many electrons can the 3rd shell hold

Answer 11

18

Question 12

how many electrons can the 4th shell hold

Answer 12

32

Question 13

what is the shape of the s orbital

Answer 13

spherical

Question 14

what shape is the p orbital

Answer 14

dumbbell

Question 15

what does the atomic emission spectra provide evidence for

Answer 15

quantum shells

Question 16

what happens in the atom when energy is emitted (2)

Answer 16

• movement of electrons

- from higher to lower energy levels

Question 17

explain why lines get closer down the atomic emissions spectrum

Answer 17

• the energy levels get closer together with increasing energy

Question 18

what happens as an electron moves from a higher to a lower quantum shell

Answer 18

• energy is released/emitted

Question 19

describe what the lines on an emissions spectrum show

Answer 19

• represent the frequencies of light that are released when an electron drop from a higher energy level to a lower one

Question 20

explain how emission spectra provides evidence that supports our current understanding of electrons existing in fixed energy levels

Answer 20

• shows that specific amount of energy are emitted when electrons drip down from higher energy levels to lower energy levels
• in-between amounts of energy are never emitted, which suggests that electrons only exist at very specific energy levels

Question 21

what is the definition of ionisation energy

Answer 21

• the amount of energy required to move 1 mole of gaseous atoms from each atom to produce 1 mole of gaseous 1+ ions

Question 22

why does first ionisation energy increase across a period

Answer 22

• number of protons in the nucleus increases as you go left to right
• but electrons enter the same energy level
• the increased charge on the nucleus means that it gets increasingly difficult to remove an electron

Question 23

why does first ionisation energy decrease down a group

Answer 23

• shielding increases as you go down a group as there are more shells
• also the electron to be removed is at an increasing distance from the nucleus and is therefore held less strongly
• therefore the outer electrons get easier to remove going down a group because they are further away from the nucleus

Question 24

why is there a drop in ionisation energy from one period to the next

Answer 24

• there is a sharp drop in the first I.E
• because at Na a new energy level is added and so there is an increase in atomic radius, the outer electron is further away from the nucleus, less strongly attracted and easier to remove

Question 25

explain the drop in first I.E between groups 2 and 3

Answer 25

e. g Mg and Al - the P electron in Al is in a higher energy level that the S electron in Mg - so it takes less energy to remove it

Question 26

explain the drop in first I.E between groups 5 and 6

Answer 26

- an electron in a pair will be easier to remove than one in an orbital on its own because it is already being repelled by the other electron - in S, it has 2 of its p electrons paired in a p-orbital so one of these will be easier to remove than an unpaired one due to the repulsion of the other electron in the same orbital