Question

If the number of electrons in an atom is 39 and the mass number for the same atom is 90, calculate the the following for this atom: a) the number of protons b) the atomic number c) the number of neutrons d) What is the identity of this element?

Answer 1

Answer:

no. of protons = 39

atomic number = number of protons = 39

number of neutrons = 51

element is Yttrium

Explanation:

given data:

number of electron is 39

mass of atom is 90

We know that atoms are neutral because +ve charged protons is equal to no of -ve charged electrons.

we know that:

atomic number is equal to number of protons,

and  atomic mass is the summation of no. of protons and  no. of neutrons

number of protons = number  of electrons

from the data given:

a) No. of protons = 39 (since number of electrons = protons)

b) atomic number = number of protons = 39

c) number of neutrons = atomic mass - atomic number

                                      = 90 - 39

                                      = 51

d) element is Yttrium