3. 1 PERIODICITY

Question 1

How is the periodic table arranged?

Answer 1

Periodic table arranged by:
-atomic number
-groups = same number outer shell electrons
-periods = number of highest energy electron shell

Question 2

What is ionisation energy?

Answer 2

Ionisation energy is the amount of energy required to remove one electron from each atom in one mole of gaseous atoms of an element
-must be gaseous as a control as it is easier to turn elements to gases than solids

Question 3

What happens to nuclear attraction across a period?

Answer 3

Across a period, the nuclear charge (number of protons) increases by one and the number of shells stays the same. This means that the nuclear attraction increases and more energy is required to remove an electron and the atomic radius decreases. This causes the ionisation energy to generally increase across a period.

Question 4

In group 2, why are boron and oxygen anomalies to ionisation energy trends.

Answer 4

Boron and oxygen are anomalies as they require less energy to loose electrons as the last subshell they fill up is further from the nucleus which causes the nuclear attraction to be slightly lower.

Question 5

What happens to ionisation energy down a group?

Answer 5

Although nuclear charge increases down a group, its effect is outweighed by the increased atomic radius and increases shielding. This means nuclear attraction decreases overall and ionisation energy decreases down a group.

Question 6

Successive ionisation energies.

Answer 6

Successive ionisation energy:
-e.g boron
-jump between 3rd ionisation energy and 4th = group 3 element
-decreased atomic radius = ratio of protons to electrons decreased so nuclear attraction increases

Question 7

What is metallic bonding?

Answer 7

Metallic bonding:
-in a solid, each atom donates its negative outershell electrons to a delocalised pool of electrons
-positive ions left behind = fixed in position to maintain shape
-electrostatic attraction between positive cations and delocalised electrons
-delocalised electrons free to move within structure

Question 8

What are properties of metallically bonded atoms?

Answer 8

Properties:
-strong metallic bonds
-high electrical conductivity (solid and liquid states)
-high melting and boiling points
-non-soluble