1.5 atomic structure and periodic table

Question 1

a What is relative atomic mass?

Answer 1

the mass of an atom averaged over its isotopes relative to 1/12 of a C-12 atom

Question 2

a What is relative isotopic mass?

Answer 2

the mass of an isotope relative to 1/12 of a C-12 atom

Question 3

b What happens within a mass spectrometer?

Answer 3

electron gun knocks electrons out of their shells, creating positive ions
these are accelerated using a negatively-charged plate
a magnetic field deflects them so that they hit detectors at the end

Question 4

b How are mass spectrometers useful?

Answer 4

more massive particles are deflected less, so the RAM can be found; this allows for one to deduce isotopic composition of an element or RMM of a compound

Question 5

d Define the term ‘first ionisation energy’.

Answer 5

the enthalpy required to form one mole of unipositive gaseous ions from the element in a monatomic gaseous state

Question 6

g Give the shape of and no. of electrons within

a) an s subshell
b) a p subshell

Answer 6

a) spherical, 2

b) three figures of eight on the xyz planes, 6

Question 7

g In what order do shells fill up?

Answer 7

1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p…

Question 8

g Describe how the p shell fills up.

Answer 8

first e- goes in one 8-shaped orbital
second and third go in the other two
thence, electrons pair up

Question 9

h Why is it easier to remove electrons from 4s than 2s?

Answer 9

further from nucleus: less attraction

electron shells between it and nucleus: more repulsion (shielding effect)

Question 10

h Why is it easier to remove an electron from a p subshell if >3 are present (as opposed to <4)

Answer 10

electrons paired up; repulsive effect within orbital

Question 11

h What happens when there are 4 or 9 electrons in a d subshell?

Answer 11

one electron is removed from the s subshell below it

Question 12

i What properties do elements within s/p/d blocks have?

Answer 12

their outermost electron is in an s/p/d subshell

Question 13

j What is a periodic property?

Answer 13

a quantity for which there is a trend across the periodic table

Question 14

j What is the trend for atomic radius and why?

Answer 14

increases towards the top-right
going right -> nuclear charge increases
going up -> number of shells decreases

Question 15

ki What is the trend for melting temperatures in groups 2 + 3 and why?

Answer 15

ionic radius increases
greater distance between nuclei and delocalised electrons
less attraction

Question 16

kii What is the trend for ionisaiton energy along a period and why?

Answer 16

general increase but drops at the start of every new subshell due to distance + shielding, and midway through filling subshells due to repulsion between paired electrons