Question

answer pls.............​

Answer 1

Explanation:

Element is Na(sodium), atomic number is written at the bottom of symbols  and mass number is written the top-left. This can found different in different books. So whenever you get this, always,

Greater one is mass number and smaller one is atomic number.

a).  Atomic number = number of electrons/protons.

So, it has 11 electrons. Hence,

Ele. config is {2, 8, 1}

b). number of e- = atomic number

                           = 11

c). number of neutrons = mass number - atomic number

                                      = 23 - 11

                                      = 12