An element x is found to have a mass number of 31 and atomic number of 17. idenrify the group and the period to which it belongs?

Well atomic number 17 is Chlorine, which is most commonly found as a gas, and is period 7.

Explanation:

elements found on period 7 are some of the most unstable elements.

because u need two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei to form isotopes.

so since they all have the same shape? i mean maybe because m& m and reeses are both chocolates