Question

bromine, chlorine, fluorine, and lodine are four elements in group 17 that can be differentiated by some of their properties. which answer choice best explains why the atomic radius of these elements increase as you go down the group?
a the number of valence electrons is increasing and electronegativity is decreasing.
b. the number of electron shells is increasing and electronegativity is decreasing.
c. the number of valence electrons is decreasing and electronegativity is decreasing.
d. the number of election shells is decreasing and electronegativity is decreasing

Explanation:

Step1: Analyze option A

Elements in Group 17 have the same number of valence electrons (7). So, the number of valence electrons is not increasing.

Step2: Analyze option B

As we go down Group 17, the number of electron shells increases (e.g., F has 2 shells, Cl has 3 shells, Br has 4 shells, I has 5 shells). And electronegativity decreases down the group (because the atomic radius increases, and the nucleus has less pull on the shared electrons).

Step3: Analyze option C

The number of valence electrons is constant (7) for Group 17 elements.

Step4: Analyze option D

The number of electron shells is increasing (not decreasing) as we go down Group 17.

Answer:

B. The number of electron shells is increasing and electronegativity is decreasing.