3.2.1 Periodicity

Question 1

how are elements in the periodic table arranged?

Answer 1

elements are arranged according to their proton number

Question 2

what is a period on the periodic table?

Answer 2

horizontal rows

Question 3

what is a group on the periodic table?

Answer 3

vertical columns

Question 4

what does group number indicate on the periodic table?

Answer 4

number of outer electrons in an element

Question 5

what are the 4 blocks of the periodic table?

Answer 5

s block
p block
d block
f block

Question 6

what elements are in each block of the periodic table

Answer 6

s block - groups 1&2
p block - groups 3 to 0
d block - transition metals
f block - radioactive elements

Question 7

what is periodicity?

Answer 7

study of trends within the periodic table
often trends are linked to elements’ electronic configurations

Question 8

what is the trend in atomic radius along a period?

Answer 8

decreases

Question 9

why does atomic radius decrease across a period?

Answer 9

increase in nuclear charge

Question 10

what is the trend in atomic radius going down a group?

Answer 10

increases

Question 11

why does atomic radius increase going down a group?

Answer 11

more shells
increased shielding

Question 12

what is the trend in ionisation energy along a period?

Answer 12

increases

Question 13

why does ionisation energy increase along a period?

Answer 13

atomic radius decreases
outer electrons held more strongly
more energy required to remove it

Question 14

what is the trend in ionisation energy going down a group?

Answer 14

decreases

Question 15

why does ionisation energy decrease going down a group?

Answer 15

atomic radius increases
more shielding
less attraction between nucleus and outer electrons
less energy required to remove it

Question 16

what does the melting point of period 3 elements depend on?

Answer 16

structure
bond strength

Question 17

what happens to melting points across period 3 between Na and Al? why?

Answer 17

increase
greater positive charge of their ions
Na = +1
Mg =+2
Al = +3

Question 18

why does the melting point increase dramatically for silicon in period 3?

Answer 18

very strong covalent structure
more energy needed to break the strong covalent bonds

Question 19

why does melting point decrease in period 3 between phosphorus and chlorine?

Answer 19

Phosphorus, sulphur and chlorine are all simple covalent molecules held together by weak VdW
less energy needed to overcome weak intermolecular forces

Question 20

why does argon have an even lower melting point than chlorine?

Answer 20

argon is a noble gas that exists as individual atoms with a full outer shell of electrons
atom is very stable
VdW between atoms is very weak
less energy needed to overcome these weak VdW forces
hence why argon is a gas at room temp.