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Chapter 4: Problem 21

In a period, from the left to right the electron affinity increases, but alkaline earth metals have lower electron affinity than alkali metals because (a) alkaline earth metals have lesser atomic radius than alkali metals. (b) alkaline earth have higher electronegativity than alkali metals. (c) alkaline earth metals have completely filled "s-" orbitals. (d) alkaline earth metals have lesser electronegativity than alkali metals.

Short Answer

Expert verified
Answer: Alkaline earth metals have lower electron affinity than alkali metals because they have completely filled s-orbitals, making it more difficult to add an electron.

Step by step solution

01

Understand the electron affinity trend

Electron affinity is the amount of energy released when an electron is added to a neutral atom to form a negative ion. In a period, electron affinity generally increases from left to right because atomic radii decrease, leading to a more positive charge felt by the valence electrons.
02

Evaluate Option (a)

Option (a) states that alkaline earth metals have a lesser atomic radius than alkali metals. While it is true that alkaline earth metals generally have smaller atomic radii than alkali metals, this fact alone cannot justify the difference in electron affinity. Moreover, smaller atomic radii usually lead to higher electron affinity, which is not the case here.
03

Evaluate Option (b)

Option (b) states that alkaline earth metals have higher electronegativity than alkali metals. Electronegativity refers to the ability of an atom to attract electrons to itself in a chemical bond, and it generally increases across a period. However, this fact is not directly related to the difference in electron affinity between alkali and alkaline earth metals.
04

Evaluate Option (c)

Option (c) states that alkaline earth metals have completely filled s-orbitals. This statement is true, as alkaline earth metals have their valence electrons in the ns^2 subshell (s-orbital with two electrons) while alkali metals have their valence electrons in the ns^1 subshell (s-orbital with one electron). Since the s-orbital is fully occupied in alkaline earth metals, it is more difficult to add an electron, thus showing lower electron affinity compared to alkali metals.
05

Evaluate Option (d)

Option (d) states that alkaline earth metals have lesser electronegativity than alkali metals. This statement is not true, as alkaline earth metals generally possess higher electronegativity than alkali metals due to their smaller atomic radii.
06

Determine the correct answer

Based on the evaluations above, option (c) is the correct answer, as it is consistent with the observed lower electron affinity in alkaline earth metals compared to alkali metals. The fully occupied s-orbital in alkaline earth metals is the main reason for this difference.

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Most popular questions from this chapter

Which of the following elements acts as the best reducing agent? (a) \(\mathrm{Na}\) (b) \(\mathrm{Cl}\) (c) \(\mathrm{Mg}\) (d) \(\mathrm{F}\)

Fill in the blanks. In the periodic table, vertical columns of elements are called ___ and horizontal rows of elements are called ___.

Which of the following sequence of explanation is appropriate for explaining the reason for the periodicity of reducing property in a period or group? (1) Tendency to undergo oxidation decreases in a period and increases in a group. (2) In a period ionization energy increases and in a group it decreases. (3) In a period the atomic size decreases and in a group it increases. (4) The elements present in the left side of the periodic table have strong reducing property. (a) 3214 (b) 3421 (c) 4312 (d) 4213

The number of valence electrons that can be present in the second element of any period is (a) 1 (b) 2 (c) 5 (d) 7

The element having the electronic configuration \([\mathrm{Kr}] 4 \mathrm{~d}^{10} 4 \mathrm{f}^{14} 5 \mathrm{~s}^{2} 5 \mathrm{p}^{6} 5 \mathrm{~d}^{2} 6 \mathrm{~s}^{2}\) belongs to (a) s-block (b) p-block (c) d-block (d) f-block
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