Question

understanding periodic trends in atomic size
re - order each list in the table below, if necessary, so that the atoms or ions in it are list
atoms or ions atoms or ions in order of decreasing size
b, o, c
ne, f, f⁻
br⁻, f⁻, i⁻

Explanation:

Step1: Recall atomic - size trend across a period

Atomic size decreases across a period from left - to - right due to an increase in effective nuclear charge. B, C, and O are in the same period (period 2). B is in group 13, C in group 14, and O in group 16. So, the order of decreasing size is B > C > O.

Step2: Consider anions and neutral atoms of the same period

For Ne, F, and F⁻, F⁻ has the largest size as it has an extra electron, increasing electron - electron repulsion. Among Ne and F, Ne has a larger effective nuclear charge pulling electrons in more tightly, but F is a neutral atom and Ne is a noble gas with a stable electron configuration. The order of decreasing size is F⁻ > F > Ne.

Step3: Recall atomic - size trend down a group for anions

For Br⁻, F⁻, and I⁻, atomic size increases down a group. I⁻ is in the 5th period, Br⁻ in the 4th period, and F⁻ in the 2nd period. So, the order of decreasing size is I⁻ > Br⁻ > F⁻.

Answer:

B, C, O
F⁻, F, Ne
I⁻, Br⁻, F⁻