What is "Atomic mass" ?

Atomic mass of an element can be defined as the number which indicates how many times the mass of one atom of the element is heavier in comparison to 1/12 th part of the mass of one atom of

Carbon-12.

What is "mole" ?

 A mole is the amount of substance that contains as many species [Atoms, molecules ions or other particles] as there are atoms in exactly 12 gm of C-12

                         [1Mole= 6.022x10^23 Species]

What are difference between "Isoelectronic" and "Isosters" species?

Isoelectronic : Ion or atom or molecule or species which have the same number of electron is called Isoelectronic species.

Isosters : Substance which have same number of electron and atoms called Isosters

What are the difference between "Kernel" and "Core" ?

 Kernel : Orbit which present after removing the outer most orbit of that atom is called kernel and electrons which is present that orbit called kernel electrons. 

Core : The outer most shell of an any atom called Core and the number of electron present of that shell is called Core electron. If the core is unstable for an atom then that atom shows variable valency. 

Nitrogen atom has Atomic number 7 & oxygen has Atomic number 8. Calculate the total number of electrons in nitrate ion