C8 - Periodicity

Question 1

What is periodicity?

Answer 1

It describes a repeating pattern in properties of elements across periods of the periodic table.

Question 2

How is the atomic radius measured for non-metals?

Answer 2

The covalent radius is often used as the atomic radius
This is half the internuclear distance between two identical atoms in a single covalent bond

Question 3

How is the atomic radius measured for non-bonded atoms?

Answer 3

The van der Waals radius is used as a value for atomic radius.
This is half the shortest internuclear distance between two similar non-bonded atoms

Question 4

How is the atomic radius measured for metals?

Answer 4

The metallic radius is often used as the atomic radius. This is half the shortest internuclear distance between two adjacent atoms in a metallic bond

Question 5

How does atomic radii change across period 3?

Answer 5

It decreases

Question 6

Why does the atomic radii change across period 3?

Answer 6

Outer electrons are all in the same energy level (n=3).
This means that shielding is similar
Proton number increases across period 3.
This causes an increase in effective nuclear charge, leading to a greater attraction between the nucleus and the outermost electrons.
This pulls these electrons closer to the nucleus resulting in smaller radii across period 3

Question 7

What is the effective nuclear charge?

Answer 7

The resultant attraction between the nucleus and the outer electrons when shielding is taken into account