Question

Mass no. Of calcium is 40 and electronic configuration is 2,8,8,2. The the no. Of neutron

Answer 1

As the electronic cpnfiguration is 2,8,8,2 the no of electrons would be 8+8+2+2=20. As the no of electrons is same as the no of protons then no of protons=20

Mass no.=No of protons + No of neutrons

40= 20 + No of neutrons

40-20= No of neutrons

Hence no of neutrons =20

Hope this helps :)

Answer 2

Atomic no. of Ca= 20 &

Mass no. Of Ca=40 &

As we know that,

No. of neutron(n)= Mass no.(M) -- Atomic no.(Z)

So, n= 40 - 20= 20

Hence, there are 20 neutrons in calcium atom.