Question

which element has the largest atomic radius: f, b, n, o?
○ n
○ o
○ b
○ f
clear my selection
23 multiple choice 1 point
which subshell would most shield valence electrons from the nucleus?
○ 1s
○ 5s
○ 4s
○ 3s
clear my selection

Explanation:

First Question (Atomic Radius):

Step1: Recall Periodic Trend

Atomic radius decreases across a period (left to right) due to increasing effective nuclear charge. B, N, O, F are in Period 2, with B at the leftmost.

Step2: Compare Positions

B (atomic number 5), N (7), O (8), F (9) – leftmost (B) has largest radius.

Step1: Shielding Concept

Electron shielding: inner electrons shield valence electrons. Subshells with higher principal quantum number (n) are further from nucleus, but for shielding valence, inner shells? Wait, no – wait, the question is which subshell most shields valence. Wait, no: shielding is when inner electrons block nucleus from valence. But the options are 1s,5s,4s,3s. Wait, no – actually, the subshell with the highest n? No, wait, no: 1s is innermost, but 5s is outer? Wait, no, I made a mistake. Wait, shielding: electrons in lower n (closer to nucleus) shield valence (higher n) electrons. But the question is "which subshell would most shield valence electrons from the nucleus?" Wait, no – maybe the question is which subshell's electrons (when present) would shield valence. Wait, no, the options are subshells: 1s, 5s, 4s, 3s. Wait, no, actually, the shielding effect: electrons in a subshell with lower n (closer to nucleus) shield electrons in higher n. But the question is which subshell (the electrons in it) would most shield valence. Wait, no, maybe the question is reversed: which subshell is most effective at shielding valence. Wait, no, the correct concept: the greater the distance from the nucleus (higher n), the less effective? No, wait, no – shielding is when inner electrons (lower n) block the nucleus's pull on outer (higher n) electrons. But the options are 1s,5s,4s,3s. Wait, no, I think I messed up. Wait, the correct answer: 1s is innermost, so electrons in 1s are closest to nucleus, so they shield valence electrons (which are in higher n) the most? No, wait, no – valence electrons are in the outermost shell. Wait, maybe the question is which subshell (if it's a core subshell) shields the most. Wait, no, the options are 1s, 5s, 4s, 3s. Wait, no, the correct answer is 1s? No, that can't be. Wait, no, I think I made a mistake. Wait, the shielding effect: the more inner electrons (lower n) there are, the more shielding. But the question is which subshell (the electrons in it) would most shield valence. Wait, no, maybe the question is which subshell is most effective at shielding. Wait, no, the correct answer is 1s? No, that's wrong. Wait, no, let's recall: shielding is the reduction of nuclear charge experienced by valence electrons due to inner electrons. So the subshell with the lowest n (closest to nucleus) has electrons that are most effective at shielding, because they are between the nucleus and the valence electrons. Wait, but 1s is the innermost, so electrons in 1s shield valence electrons (in higher n) the most. But the options are 1s,5s,4s,3s. Wait, but 5s is a valence subshell (if n=5 is the outermost). Wait, no, the question is "which subshell would most shield valence electrons from the nucleus?" So the subshell whose electrons are between the nucleus and the valence electrons. So the lower the n, the closer to nucleus, so more shielding. So 1s is the innermost, so electrons in 1s shield the most. But that seems correct. Wait, but I think I was wrong earlier. Let me check: shielding effect increases with the number of inner electrons, and the subshells closer to the nucleus (lower n) have electrons that are more effective at shielding. So 1s electrons are closest to nucleus, so they shield valence electrons (in higher n) the most. So the answer is 1s.

Answer:

C. B

Second Question (Shielding Subshell):