Question

question 1: which of the following elements have a smaller atomic radius than phosphorus (p)? select all that apply

• indium (in)
• chlorine (cl)
• silicon (si)
• oxygen (o)
• sodium (na)
• nitrogen (n)

Explanation:

Step1: Recall atomic radius trends

Atomic radius decreases across a period (left to right) and increases down a group (top to bottom) in the periodic table. Phosphorus (P) is in period 3, group 15.

Step2: Analyze each element

- **Helium (He)**: Noble gas, much smaller (period 1, group 18) – smaller than P.
- **Chlorine (Cl)**: Period 3, group 17 (right of P) – smaller (decreases across period).
- **Silicon (Si)**: Period 3, group 14 (left of P) – larger (increases left to right).
- **Oxygen (O)**: Period 2, group 16 (above P, same group trend? Wait, period 2 vs 3: O is period 2, P period 3. Down a group, radius increases, so O (period 2) is smaller than P (period 3).
- **Sodium (Na)**: Period 3, group 1 (left of P) – larger (increases left to right).
- **Nitrogen (N)**: Period 2, group 15 (above P) – smaller (down a group, radius increases, so N < P). Wait, wait, original question: "smaller than phosphorus (P)"? Wait, wait, the question says "phosphorus (P)"? Wait, no, maybe a typo? Wait, the options: Helium, Chlorine, Silicon, Oxygen, Sodium, Nitrogen. Wait, maybe the question is "smaller than phosphorus (P)"? Wait, no, maybe "phosphorus (P)" is a typo, maybe "phosphorus (P)" or maybe "phosphorus (P)" but let's check again. Wait, no, the user's image: "smaller atomic radius than phosphorus (P)?". Wait, but let's recheck:

Wait, correct trends:

- Across period 3 (Na, Si, P, S, Cl): atomic radius decreases from Na to Cl. So Cl (right of P) is smaller than P.

- Down group 15: N (period 2) < P (period 3) < As, etc. So N is smaller than P.

- O is period 2, group 16. P is period 3, group 15. O is to the right of N (group 15) in period 2, so O < N. Since N < P, O < P.

- He is period 1, group 18 – much smaller than P.

Wait, but the options: Helium (He), Chlorine (Cl), Silicon (Si), Oxygen (O), Sodium (Na), Nitrogen (N).

Wait, but the question says "smaller than phosphorus (P)". Let's re-express:

- He: smaller (period 1, tiny).
- Cl: period 3, group 17 (right of P) – smaller.
- Si: period 3, group 14 (left of P) – larger.
- O: period 2, group 16 (above and right of P's group) – smaller.
- Na: period 3, group 1 (left of P) – larger.
- N: period 2, group 15 (above P) – smaller (since down group 15, radius increases: N < P).

Wait, but the original question: maybe the user made a typo, but assuming the question is correct, the elements with smaller atomic radius than P are He, Cl, O, N? Wait, no, wait, let's check again. Wait, the question says "phosphorus (P)" – but let's confirm each:

1. Helium (He): Atomic radius ~31 pm, P ~107 pm – smaller.

2. Chlorine (Cl): ~99 pm, P ~107 pm – smaller.

3. Silicon (Si): ~111 pm, P ~107 pm – larger (wait, Si is 111, P is 107? Wait, no, maybe my memory is wrong. Wait, actual atomic radii (empirical):

Na: ~186 pm

Si: ~111 pm

P: ~107 pm

S: ~105 pm

Cl: ~99 pm

So Si (111) is larger than P (107). So Si is larger.

O: ~66 pm

N: ~71 pm

He: ~31 pm

So:

He (31) < P (107) – yes.

Cl (99) < P (107) – yes.

Si (111) > P (107) – no.

O (66) < P (107) – yes.

Na (186) > P (107) – no.

N (71) < P (107) – yes.

Wait, but the options: the checkboxes. So the correct ones are Helium (He), Chlorine (Cl), Oxygen (O), Nitrogen (N)? Wait, but maybe the question had a typo, like "phosphorus (P)" should be "phosphorus (P)" or maybe "phosphorus (P)" but let's proceed.

But the user's question: "Which of the following elements have a smaller atomic radius than phosphorus (P)? Select all that apply".

So the correct options are:

- Helium (He)

- Chlorine (Cl)

- Oxygen (O)

- Nitrogen (N)

Wait, but let's check again. Wait, Si: 111 vs P:107 – Si is larger. Na:186 larger. So the correct ones are He, Cl, O, N.

But maybe the original question had a typo, like "phosphorus (P)" should be "phosphorus (P)" but let's confirm.

Answer:

A. Helium (He)
B. Chlorine (Cl)
D. Oxygen (O)
F. Nitrogen (N)

(Assuming the options are labeled A-F as: A. Helium (He), B. Chlorine (Cl), C. Silicon (Si), D. Oxygen (O), E. Sodium (Na), F. Nitrogen (N))