Unit 1: Periodicity

Question 1

Metallic bonding

Answer 1

Electrostatic attraction between positive metal ion cores and a sea of delocalised electrons.
Structure: Lattice of cores

Question 2

Covalent bonding

Answer 2

Electrostatic attraction between positive nuclei and the shared pair of electrons between them.
Structure: Network lattice or discrete molecule

Question 3

Monatomic bonding

Answer 3

Single atoms

Structure: single atoms

Question 4

Covalent radius

Answer 4

A measure of the size of an atom. It is measured as half the distance between two nuclei in a bond.

Question 5

Covalent radius across a period trend

Answer 5

Across a period, the covalent radius decreases. This is because of the increasing nuclear charge. As you go across a period, a proton is added to the same shell. Increased nuclear charge within the nucleus pulls the electrons in tighter.

Question 6

Covalent radius down a group trend

Answer 6

Down a group, the covalent radius increases. This is because as you go down a group, a new shell is being filled for each row, so the atom is bigger. The inner filled shells also shield or screen the outer electrons from the increased nuclear charge.

Question 7

First ionisation energy

Answer 7

The first ionisation energy is the energy required to remove one mole of electrons from one mole of atoms in the gaseous state.
E(g) —> E^+(g) + e^-

Question 8

Second ionisation energy

Answer 8

The second ionisation energy is the energy required to remove one mole of electrons from one mole of positive ions in the gaseous state.
E^+(g) —> E^2+ + e^-

Question 9

Ionisation across a period trend

Answer 9

Across a period first ionisation energy increases. This is because of the increasing nuclear charge. This holds the electrons more strongly.

Question 10

Ionisation down a group trend

Answer 10

Down a group first ionisation energy decreases. This is because of the screening or shielding effect. Going down a group the nuclear charge increases but the outer electrons are shielded from it by full electron shells between the nucleus and the outer shell. An extra shell is added for each period.

Question 11

Electronegativity

Answer 11

A measure of the attraction of an element for bonding electrons. The higher the electronegativity value of an element, the stronger its attraction for electrons.

Question 12

Electronegativity across a period trend

Answer 12

Across a period, electronegativity increases. This is because of increased nuclear charge

Question 13

Electronegativity down a group trend

Answer 13

Down a group, electronegativity decreases. This is because of the screening/shielding effect.

Question 14

Diamond vs. carbon

Answer 14

Diamond: Each atom is covalently bonded to four other carbon atoms in a tetrahedral arrangement. All four atoms are in a bond.
Carbon: Each atom is covalently bonded to three other atoms in layers of hexagonal rings. The fourth outer electron is delocalised, allowing it to conduct electricity. Layers are held together by weak LDF forces.

Question 15

How are elements arranged in the periodic table?

Answer 15

In order of increasing the atomic number

Question 16

Groups

Answer 16

Vertical columns contain elements with similar chemical properties and chemical behaviour from a common number of electrons in the outer shell.