Question

an atom X has 17 protons and 18 neutrons. write its atomic number and mass number.

Answer 1

hey dear
here is your answer

no. of protons = no. of electrons & no. of electrons = atomic number so, no. of protons = atomic no.
so, atomic number = 17
& atomic mass = no. of protons + no. of neutrons
so , atomic mass = 17+18 = 35

hope it helps ☺

Answer 2

Atomic number = number of protons(or electrons)(exception, Hydrogen)=17
Mass number=Protons +neutrons=17+18=35 amu.
Here this Element is Chlorine but as chlorine have isotopes so it's average mass is considered as 35.5 amu.
Hope I have helped You.