Give a reason for the following. Ionisation potential increases across a period, from left to right.

Across a period atomic size decreases and nuclear charge increases, hence more energy is required to remove the valence electrons. Therefore, ionisation potential increases. Thus, the ionisation energy decreases from top to bottom in groups and increases from left to right across a period in the periodic table.

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All in One - ICSE Chemistry>Chapter 1 - Periodic Properties and Their Variations>ARCHIVES* (Last 6 Years)>Q 15

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Ionisation potential increases across a period from left to right because the

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Important Questions on Periodic Properties and Their Variations

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All in One - ICSE Chemistry>Chapter 1 - Periodic Properties and Their Variations>ARCHIVES* (Last 6 Years)>Q 16

Name the element which has the highest ionisation potential.

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All in One - ICSE Chemistry>Chapter 1 - Periodic Properties and Their Variations>ARCHIVES* (Last 6 Years)>Q 17

Among the elements of period

2

, the element which has high electron affinity is

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All in One - ICSE Chemistry>Chapter 1 - Periodic Properties and Their Variations>ARCHIVES* (Last 6 Years)>Q 18

Answer any five questions.

Group number	$I A$	$I I A$	$I I I A$	$I V A$	$V A$	$V I A$	$V I I A$	$0$
Period	$1$	$2$	$13$	$14$	$15$	$16$	$17$	$18$
Second	$L i$		$D$			$O$	$J$	$N e$
Third	$A$	$M g$	$E$	$S i$		$H$	$M$
Fourth	$R$	$T$	$I$		$Q$	$U$		$Y$

Note: In this table, $H$ does not represent hydrogen. Some elements are given in their own symbol and position in the periodic table while others are shown with a letter.
With reference to the above table answer the following questions.
(i) Identify the most electronegative element.

(ii) Identify the most reactive element of group $1$ .

(iii) Identify the element from period $3$ with the least atomic sizes.

(iv) How many valence electrons are present in $Q$ ?

(v) Which element from group $2$ would have the least ionisation energy?

(vi) Identify the noble gas of the fourth period.