Question

At STP, an element that is a brittle solid and a poor conductor of heat and electricity could have an atomic number of

(1) 12 (3) 16
(2) 13 (4) 17

Answer 1

The element with atomic number 16, which is sulfur (S), is a brittle solid and a poor conductor of heat and electricity at STP, fitting the description given in the question.

Step-by-step explanation:

At STP (Standard Temperature and Pressure), an element that is a brittle solid and a poor conductor of heat and electricity is most likely to be a nonmetal. Among the given options with atomic numbers 12 (Mg), 13 (Al), 16 (S), and 17 (Cl), sulfur (S) with an atomic number of 16 is the one that fits this description. Magnesium (Mg) and Aluminum (Al), with atomic numbers 12 and 13 respectively, are metals and are not typically brittle nor poor conductors. Chlorine (Cl), with atomic number 17, is a gas at STP and thus cannot be described as a solid at all.

The answer is 16, corresponding to sulfur.

Answer 2

(3) 16, which is Sulfer.