Atomic no.: 17
Electronic configuration: 2,8,7
Group no.: 7
Period no.: 3
valency: 1-
Mass no. is the sum of protons and neutrons. Atomic no. is the number of protons. to find the atomic number, we need to subtract the Mass no. from the no. of neutrons (35-18)
The no. of electrons in the last shell of element x is 7, therefore it belings to group VII
Element x has 3 electron shells, therefore, it belongs to period no. 3
Element x belings to group VII (7), so to find its valency, we say 8-7=1. and Element x is Chlorine, chlorine is a non-metal, non-metals gain electrons. an ion that gained electrons is a negatively charged ion. therefore the valency of element x is -1 or 1-