Answer
a) 40 protons, 40 electrons and 50 neutrons.
b) 82 protons, 82 electrons and 126 neutrons.
Work Step by Step
a) Referring to the periodic table, we find that the atomic number Z of Zr is 40.
Number of protons= Number of electrons in the neutral atom= Z= 40.
Superscript at the left of the atomic symbol is the mass number.
Number of neutrons= A-Z= 90-40= 50.
b) Z= 82= Number of protons= Number of electrons in the neutral atom.
Neutron number= A-Z= 208-82= 126.
