Compare the following sodium atoms in terms of their neutrons and mass numbers 24Na, 23Na

Na-24 and Na-23 have the same number of atoms=11, different neutrons(13 and 12),different mass number(24 and 23)

The elements in nature have several types of isotopes

Isotopes have the same number of protons and having a different number of neutrons.

So Isotopes are elements that have the same Atomic Number (Proton)

number of atoms = 11

mass number = 23

number of neutrons=23-11=12

number of atoms = 11

mass number = 24

number of neutrons=24-11=13

we can conclude that the melting point of table salt is above room temperature (it's actually 801 deg c). the melting point of mercury must be below room temperature (- 39 deg c).