Question

1. bromine is a highly reactive liquid, while krypton is an inert gas. explain the difference based on their electron configurations. 82. potassium is a highly reactive

Explanation:

For Question 81:

Bromine (Br) has an electron configuration that results in it needing to gain an electron to achieve a stable octet (its valence shell has 7 electrons). This makes it highly reactive as it readily reacts to gain that electron. Krypton (Kr) has a full valence shell (8 electrons, a stable octet), so it has no tendency to gain or lose electrons, making it inert (chemically unreactive). The electron configuration of Br is $[Ar] 3d^{10} 4s^{2} 4p^{5}$, and for Kr it is $[Ar] 3d^{10} 4s^{2} 4p^{6}$ (or a noble gas configuration), which explains their reactivity difference.

Potassium (K) has an electron configuration of $[Ar] 4s^{1}$. It has 1 valence electron in its outermost shell. To achieve a stable electron configuration (like the noble gas argon, $[Ar]$), potassium readily loses this single valence electron. This tendency to lose an electron makes it highly reactive, especially in forming ionic compounds or reacting with non - metals (e.g., reacting vigorously with water or oxygen).

Answer:

Bromine has 7 valence electrons (electron config: $[Ar] 3d^{10} 4s^{2} 4p^{5}$), so it reacts to gain 1 electron for a stable octet. Krypton has a full valence shell (8 electrons, config: $[Ar] 3d^{10} 4s^{2} 4p^{6}$), so it is inert as it has no need to gain/lose electrons.

For Question 82 (assuming the full question is about potassium's reactivity, likely comparing to a less reactive element like argon or another, but based on given start):