Periodic trends - covalent radius

Question 1

Trends in atomic size can be explained in terms of

Answer 1

Nuclear charge
Shielding of outer electrons by inner ones
Number of electron shells

Question 2

Across a period the covalent radius of an atom …

Answer 2

Decreases

Question 3

Down a group the covalent radius of an atom …

Answer 3

Increases

Question 4

Definition of atomic size/ covalent radius

Answer 4

A measure of how large individual atoms are

Question 5

Why does covalent radius of an atom decrease across a period in the periodic table?

Answer 5

As you go across a period, the nuclear charge increases which exerts a greater attraction on the outer electrons, pulling them in more tightly, resulting in a smaller covalent radius.

Question 6

Why does the covalent radius of an atom increase down a group in the periodic table?

Answer 6

As you go down a group the size of the atom increases as the atoms have an increasing number of electron shells, meaning they’re further away from the nucleus’s charge - decreasing the strength of attraction on the outer electrons. The inner shells also shield/screen the outer ones from the charge of the nucleus meaning they are not as tightly pulled towards the nucleus - increasing the covalent radius/ atomic size.

Question 7

Why is the ionic radius of an atom different to the covalent radius

Answer 7

Ionic bonds involve outer electrons either being gained or lost - if they are lost it will decrease the number of outer shells decreasing the shielding and increasing the attraction between the nucleus and the outer electrons making these electrons being pulled tighter meaning it will be smaller.