3.1 periodicity

Question 1

periodic table order

Answer 1

proton number

Question 2

ionisation

Answer 2

ionisation energy is the minimum amount of energy required to removed 1 mole of electrons from 1 mole of gaseous atoms

Question 3

is ionisation endo or exo?

Answer 3

ionisation requires energy so they are always an endothermic reaction and have a positive value

Question 4

shielding

Answer 4

more electron shells between nucleus and outer electron means less energy is required to remove electron as there is weaker attraction

Question 5

nuclear charge

Answer 5

more protons in nucleus means there is stronger nuclear attraction between nucleus and outer electrons meaning more energy required to remove electron

Question 6

atomic radius

Answer 6

the larger the atom, the further away the outer electrons are from the nucleus so there is a weaker nuclear attraction and less energy is required to remove electrons

Question 7

trend in ionisation energy down group

Answer 7

decreases
atomic radius increases down group
shielding increases down group
nuclear attraction becomes weaker therefore less energy is required to remove an electron

Question 8

how do trends in ionisation energy support the Bohr model of the atom?

Answer 8

successive ionisation energies reflect the arrangement of electrons in shells, but doesn’t explain sub-shells

Question 9

trend in ionisation energy across period

Answer 9

increases
proton number increases across period therefore nuclear attraction increases
shielding is similar
more energy is required to remove an outer electron

Question 10

aluminium ionisation trend

Answer 10

outer most electron in Al sits in a higher energy sub-shell further from the nucleus than the outer electron in Mg
Mg - 1s2, 2s2, 2p6, 3s2 (3s sub-shell)
Al - 1s2, 2s2, 2p6, 3s2, 3p1 (3p sub-shell)

Question 11

sulfur ionisation trend

Answer 11

P and S both have outer electrons in the 3p orbital so shielding is the same
Removing an electron from S involves taking it from an orbital with 2 electrons in
Electrons repel each other therefore less energy is needed to remove energy from orbital with 2 electrons than 1 electron like in P

Question 12

successive ionisation

Answer 12

the removal of more than 1 electron from the same atom

Question 13

trend in successive ionisation energy

Answer 13

general increase in energy as removing an electron from an increasingly more positive ion and removing electrons from shell closer to nucleus where there is stronger nuclear attraction

Question 14

graphite

Answer 14

each C atom bonded 3 times with one delocalised electron
very high melting point due to many strong covalent bonds
layers slide as there are weak forces between layers
layers far apart in comparison to covalent bond length, low density
delocalised e- between layers allow graphite to conduct electricity as they carry charge
graphite is insoluble, covalent bonds too strong to break

Question 15

diamond

Answer 15

each C atom bonded 4 time (tetrahedral)
tightly packed and rigid arrangement allows heat to conduct well
very high melting point due to many strong covalent bonds, also very hard
diamond doesn’t conduct electricity since it has no delocalised electrons

Question 16

graphene

Answer 16

1 layer of graphite
1 atom thick (lightweight and transparent)
hexagonal carbon rings
delocalised electrons allows for graphene to conduct electricity as they carry charge
delocalised electrons strengthen covalent bonds, high strength property

Question 17

uses of graphene

Answer 17

• aircraft shells
• super/highspeed computers
• smartphone screens

Question 18

metallic bonding (metals)

Answer 18

positive metal ions are formed as metals donate electrons
electrostatic attraction between positive metal ions and negative delocalised e-
the more electrons an atom can donate, the higher melting point
good electrical conductors as delocalised electrons are mobile and can carry charge
good thermal conductors as delocalised e- can transfer kinetic energy
high melting points due to strong electrostatic attraction
solid metals are insoluble as metallic bond is too strong to break

Question 19

melting point trend across period 3

Answer 19

general increase as metal ions have increasing positive charge
increasing number of delocalised electrons
smaller atomic radius
this means stronger metallic bond

Question 20

Si melting point

Answer 20

highest melting point in period 3as it has a giant covalent (macromolecular) structure
many strong covalent bonds hold the silicon atoms together
large amount of energy needed to overcome these strong covalent bonds

Question 21

P melting point

Answer 21

P4 formula
lower melting point than Si due to weaker simple molecular structure
melting point determined by weaker induced dipole-dipole forces

Question 22

S melting point

Answer 22

S8 formula
higher melting point than P due to larger simple molecular structure
larger induced dipole-dipole forces

Question 23

Cl melting point

Answer 23

Cl2 formula
lower melting point than P and S due to smaller simple molecular structure
smaller induced dipole-dipole forces

Question 24

Ar melting point

Answer 24

Ar formula
lower melting point than all other elements in period 3 because it only exists as an individual atom
smaller induced dipole-dipole forces

Question 25

are simple molecular/simple covalent structures soluble in water?

Answer 25

depends on the polarity of the molecule
polar molecules dissolve well in polar solvents like water
non-polar molecules do not

Question 26

why do noble gases have low melting points?

Answer 26

more electrons leads to a smaller atomic radius meaning it has a higher electron charge density so the repulsion forces between the particles lower the energy needed to overcome the intermolecular forces