Question

The size of boron is ________ than that of oxygen and ________ than that of aluminum.

What is the trend in atomic size in the series of Group IIA elements Be through Ra?

Atomic size increases at first, then decreases in this series.
	Atomic size increases in this series.
	Atomic size decreases in this series.
	Atomic size remains unchanged in this series.

Ionization energy _____ as one goes down a group and _____ as one goes from left to right in a period.

Answer 1

1.The size of boron is larger than that of oxygen and smaller than that of aluminum.

Boron is 13th group, second period element and oxygen is 16th group, second period element

Aluminium is also 13th group element but it lies in 3rd period

Because atomic size decreases from left to right in a period. But Aluminum is larger in size than boron because Aluminium is a Third period element.

• as number of shell increases atomic size increases.
• Period number represent the number of shell in a given element.

2. Top to bottom in a series say IIA from Be to Ra atomic size increases in this series because number of shell increases top to bottom in a series due to period number increases top to bottom.

3. Ionization energy decreases as one goes down a group and increases as one goes from left to right in a period.

Because top to bottom in a group atomic size increases therefore effective nuclear charge on Valence shell electron decreases. So removal of electron require less energy.

And, left to right in a period atomic size decreases therefore effective nuclear charge on Valence shell electron increases. So removal of electron require more energy.