Periodicity

Question 1

how are elements ordered on the periodic table?

Answer 1

atomic number

Question 2

what are metalloids?

Answer 2

elements with both metal and non metal properties

Question 3

how does the reactivity of s-block elements change going down the group?

Answer 3

s-block elements get more reactive going down the group

Question 4

how does the reactivity of non-metals elements change going down the group?

Answer 4

non-metals get less reactive going down the group

Question 5

describe how atomic radius changes across a period. why?

Answer 5

• decreases across a period
• increasing number of protons = increased nuclear charge
• pulls outer shell of electrons towards the nucleus
• shielding has little effect as it is similar across the period

Question 6

describe how atomic radius changes down a group. why?

Answer 6

• increases down a group
• more shells

Question 7

describe and explain the change in melting points across the first 3 period 3 elements

Answer 7

• first 3 elements of p3 metals so metallic bonding
• general inc in mp as metal ions have an inc pos charge, inc delocalised e and smaller ionic radius resulting in strong metallic bond (need more energy to break)

Question 8

which period 3 element has the highest melting point? explain why

Answer 8

• silicon has highest mp in p3
• has a macromolecular/giant covalent structure = many strong covalent bonds holding Si atoms together
• large amount of energy needed to overcome these strong covalent bonds

Question 9

describe how the melting point of phosphorus differs from silicon? what is the formula of phosphorus?

Answer 9

• lower mp than Si bc simple molecular structure held together by weak intermolecular forces
• P₄

Question 10

describe how the melting point of sulfur differs from phosphorus? what is the formula of sulfur?

Answer 10

• higher mp than phosphorus as larger simple molecular structure = larger vdw forces = more energy needed
• S₈

Question 11

describe how the melting point of chlorine differs from sulfur? what is the formula of chlorine?

Answer 11

• lower mp as smaller simple molecular structure
• smaller vdw
• Cl₂

Question 12

describe how the melting point of argon differs from chlorine? what is the formula of argon?

Answer 12

• lower mp as exists only as individual atoms
• smaller vdw = smaller mp
• Ar

Question 13

describe and explain the general trend in ionisation energy going down a group

Answer 13

• decreases down group
• atomic radius increases as go down group as outer e further from nucleus
• attractive forces weaker so less energy required to remove electron
• shielding inc as go down (more shells between nucleus and outer shell)
• attractive forces weaker so less energy required to remove electron

Question 14

describe and explain the general trend in ionisation energy going across a period

Answer 14

• increases across a period
• increased nuclear charge = inc nuclear attraction = more energy required to remove outer e

Question 15

give an example of evidence of atoms having subshells

Answer 15

• a decrease in the I.E at aluminium in p3
• outermost e in Aluminium sits in higher energy subshell slightly further from the nucleus than the outer e in magnesium

Question 16

give an example of evidence of electron repulsion in an orbital

Answer 16

• phosphorus and sulfur both have outer e in 3p orbital, so shielding is the same
• removing an e from sulfur involves taking it from an orbital with 2 e in
• e repel each other so less energy needed to remove an e from an orbital with 2 e in than an orbital with 1 e in (like phosphorus)