Question

element A has 4 valence electrons and has 3 shells
a. Find the atomic number of element A
b. Calculate the number of neutrons of A if it’s mass number is 28

Answer 1

Answer:

a. 14

b. 14

Explanation:

a. Total number of electrons in 1st shell                              = 2

   Total number of electrons in 2nd shell                            = 8

   Number of electrons in 3rd shell (as given in question) = 4

Thus, total number of electrons = 2+8+4 = 14

And,

⇒Atomic number = Total number of electrons

                          = 14

b. Number of protons = number of electrons

                                    = 14

And,

⇒ Number of protons + Number of neutrons = Mass number

⇒ Number of neutrons = Mass number - Number of protons

                                       = 28 - 14

                                       = 14

Hope this helps!!