Question

which of the following would you put in box a? * (0.5 points) s block d block p block f block 1 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁵ 2 1s²2s²2p⁴ 3 1s² 4 xe6s²4f⁴ 5 1s²2s²2p⁶3s²3p⁶4s²3d⁷ 6 ne3s²

Explanation:

Step1: Recall s - block elements' electron configuration

s - block elements have their outermost electrons in s - orbitals. The general form of electron configuration for s - block elements (excluding He) is \(ns^{1 - 2}\). For He, it is \(1s^{2}\).

Step2: Analyze each option

• Option 1: \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{5}\) has electrons in p and d orbitals (not just s), so it is not an s - block element.
• Option 2: \(1s^{2}2s^{2}2p^{4}\) has electrons in p orbitals (not just s), so it is not an s - block element.
• Option 3: \(1s^{2}\) (He) is an s - block element (though in the p - block in some modern periodic table group - wise classification, based on electron - filling, it has only s - orbital electrons filled initially).
• Option 4: \([Xe]6s^{2}4f^{4}\) has electrons in f orbitals (not just s), so it is not an s - block element.
• Option 5: \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{7}\) has electrons in d orbitals (not just s), so it is not an s - block element.
• Option 6: \([Ne]3s^{2}\) (Mg) is an s - block element as its outermost electrons are in the 3s orbital.

Answer:

6