Periodicity

Question 1

what does periodicity mean?

Answer 1

repeating trends of physical or chemical properties with increasing atomic number

Question 2

describe the structure and bonding of metals Na, Mg and Al

Answer 2

• giant metallic lattice with strong metallic bonds
• metallic bonding = high melting and boiling point

Question 3

describe the structure and bonding of silicon

Answer 3

• giant covalent (macromolecular) with strong covalent bonds
• covalent bonding = very high melting and boiling point

Question 4

describe the structure and bonding P, S, and Cl

Answer 4

• simple molecular with strong covalent bonds but weak intermolecular forces
• weak VdW forces = low melting and boiling point

Question 4

what 3 things affect metallic bonding

Answer 4

• atomic radius
• amount of delocalised electrons
• charge on metal ion

Question 4

describe the structure of Ar

Answer 4

• simple molecular with strong covalent bonds but weak intermolecular forces
• monoatomic
• weak VdW forces = low melting and boiling point

Question 5

what 2 things affect VdW forces

Answer 5

• size of molecule
• surface area contact of molecule

Question 5

describe + explain the trend in melting and boiling points across period 3 metals

Answer 5

• ion charge and delocalised electrons increase
• atomic radius decrease
• metallic bonding gets stronger across the period
• melting and boiling point increase across the period

Question 5

describe + explain the melting and boiling points of period 3 simple molecular substances

Answer 5

• VdW forces increase with the size of a molecule
• melting/boiling point increases with increase in VdW forces
• size trend = sulphur > phosphorous > chlorine > argon

Question 6

why does atomic radius increase down a group

Answer 6

• there is an increase in principle energy levels

Question 6

why does silicon have a very high melting + boiling point

Answer 6

• silicon has a macromolecular structure formed by covalent bonding
• there are strong covalent bonds throughout the whole structure
• high energy to overcome bonds = high melting/boiling point

Question 7

what is ionisation energy

Answer 7

the minimum amount of energy required to remove 1 mole of electrons form one mole of atoms in a gaseous state

Question 8

why does atomic radius decrease across a period

Answer 8

• number of protons increase
• shielding is constant
• electrons are more strongly attracted to the nucleus resulting in a smaller atomic radius

Question 9

how does ionisation energy change down a group

Answer 9

• electrons removed from a higher principal energy level
• more shielding = further distance between nucleus and valence electrons
• weaker attraction = less energy to remove electron
• decreases

Question 10

General trend of ionisation energy across a period

Answer 10

• increases
• shielding is constant, protons increase
• greater attraction = more energy to remove electron

Question 11

what are two examples of when the general trend of ionisation energy across a period is disrupted?

Answer 11

• between magnesium and aluminium
• between phosphorus and sulphur

Question 12

Why does sulphur have a lower first ionisation energy than phosphorus?

Answer 12

• the electron in sulphur is removed from an energy p sub-level with a pair of electrons which repulse each other
• this extra repulsion means it takes less energy to remove one of them

Question 12

why does aluminium have a lower ionisation energy than magnesium?

Answer 12

• electron is removed from a higher energy p sublevel which takes less energy