Question

Arrange the following in order of decreasing first ionisation energy K, Mg, Mg²+,Na
(1) Mg2+ > Mg > Na> K
(2) K> Na > Mg2+ > Mg
(3) K > Mg > Na > Mg²+
(4) K > Na > Mg > Mg²+​

Answer 1

Answer:

Arrange the following in order of decreasing first ionisation energy K, Mg, Mg²+,Na

(1) Mg2+ > Mg > Na> K

(2) K> Na > Mg2+ > Mg

(3) K > Mg > Na > Mg²+

(4) K > Na > Mg > Mg²+

.Answer :-4 th

Explanation:

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Answer 2

Arranging the following in order of decreasing first ionization energy K, Mg, Mg²+, Na gives:-

Mg2+ > Mg > Na> K

• The first ionization energy of Na is greater than K because there are 4 electron shells in K while only 3 shells in Na. Thus, there is a greater shielding effect in K and less energy is required to remove an electron.
• The size of Mg is smaller than Na, thus greater energy is required to remove an electron from its shell as compared to that of Na. In Mg²⁺, electrons will be more attracted to the nucleus and their removal will be more difficult.
• Thus the order of electron gain enthalpy will be: Mg2+ > Mg > Na> K