Question

the atom of an element is made up of 4protons,5 newtrons and 4 electron.what is its atom number and mass number

Answer 1

atomic number is the no. of electrons or protons.
so atomic no. is 4

atomic mass no. is sum of number of protons and newtrons.
so it is 4+5 = 9

Answer 2

The atomic number offcourse related to the number of protons so the atomic number is 4…but i want to clearify that the mass is of two types that is atomic mass and mass number. The mass number is the sum of protons and neutrons in an atom, but the atomic mass is the average mass of all the isotopes of the that element according to percentage abundance of each isotope so,the atomic mass will always be in decimal points. The answer you asked is about an alkaline earth metal berillium which has 5 isotopes with mass numbers 7,8,9,10 and 11 and according to their percentage abundance the atomic mass of berillium is 9.012 a.m.u. whereas the mass number of each isotope will be different due to different number of neutrons in each isotope.

I hope it help you ☺️