Question

An anion A 3- has 18 electrons .write the atomic number of A

Answer 1

since this is an ion we need to first add or subtract electrons from it to gain the proper atom. this is anion meaning an atom which has taken electrons. thus we will subtract electrons to get its original number of electrons. therefore Element A has 15 electrons and we know that
number of electrons= number of protons=atomic number

thus A has atomic number 15 and electronic configuration 2,8,5

hope this helps you!! :)

Answer 2

Answer:

Expl Atomic number-21