Question

1. circle the atom in each pair with the larger radius:

a) mg or ca
b) c or si
c) cl or br
d) li or f

1. using the periodic table, predict which has the larger atomic radius: phosphorus (p) or sulfur (s). explain your reasoning.
2. true or false: atomic radius decreases across a period because the number of energy levels decreases.

Explanation:

Step1: Recall atomic - radius trends

Atomic radius increases down a group and decreases across a period.

Step2: Analyze pair a) Mg and Ca

Mg and Ca are in the same group (Group 2). Ca is below Mg, so Ca has a larger atomic radius.

Step3: Analyze pair b) C and Si

C and Si are in the same group (Group 14). Si is below C, so Si has a larger atomic radius.

Step4: Analyze pair c) Cl and Br

Cl and Br are in the same group (Group 17). Br is below Cl, so Br has a larger atomic radius.

Step5: Analyze pair d) Li and F

Li and F are in the same period (Period 2). Li is to the left of F, and atomic - radius decreases across a period, so Li has a larger atomic radius.

Step6: Analyze P and S

P and S are in the same period (Period 3). P is to the left of S. Since atomic radius decreases across a period, P has a larger atomic radius. The reason is that as you move across a period, the number of protons increases, which increases the nuclear charge, pulling the electrons closer to the nucleus.

Step7: Analyze the statement in question 20

The statement "Atomic radius decreases across a period because the number of energy levels decreases" is False. Atomic radius decreases across a period because the number of protons increases, increasing the effective nuclear charge, which pulls the electrons in the same energy level closer to the nucleus. The number of energy levels remains the same across a period.

Answer:

a) Ca
b) Si
c) Br
d) Li

1. P; because atomic radius decreases across a period and P is to the left of S in Period 3.
2. False