A scientist studies an element that has seven electrons in its outer shell, is fairly toxic, is a gas at room temperature, and is highly reactive. To which group of the periodic table does this element belong?

Question

1. 18 - noble gases
2. 17 - halogens
3. 2 - alkaline earth metals
4. 1 - alkali metals

Answer 1

The element described in the question, with seven electrons in its outer shell, being toxic, a gas at room temperature, and highly reactive, belongs to group 17 of the periodic table, which is the halogens. Therefore, the correct answer is option 2 - 17: halogens.