3.2.1 Periodicity

Question 1

What is periodicity?

Answer 1

The repeating pattern of physical/chemical properties going across the periods

Question 2

What is the trend of atomic radius across a period?

Answer 2

Atomic radii decrease from left to right across a period.

This is due to:
1. Increasing Nuclear Charge
2. Similar Shielding

The increased number of protons create more positive charge attraction for electrons which are in the same shell for each of the elements in the period.

Question 3

Explain the trend of m.p/b.p across period 3 (5)

Answer 3

Na -> Mg -> Al - Metallic Bonding is very strong, this gets stronger the more electrons there are in the outer shell, as they are more delocalised electrons. This means there is greater attraction between the electrons and the nucleus, hence more energy is needed to break teh bonds.

Si (highest) - Macromolecular - many strong covalent bonds, high energy needed to break covalent bonds

(drops)

P4, S8, Cl2 - simple molecular : weak van der waals between molecules, so little energy is needed to break them – low mp+ bp

There is an increase in mp/bp from P to S as S8 has more electrons, hence stronger VDW forces

Ar is monoatomic weak van der waals between atoms

Question 4

What does the block of an element tell you?

Answer 4

The sub shell in which the highest energy electron is in