How many protons, neutrons, and electrons are in a neutral atom of sodium?

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Protons 11
Neutrons 12
Electrons 11

The subatomic particles (protons, neutrons and electrons) can be calculated using some basic information from the periodic table.

The Atomic Number of an element is always equal to the number of protons. The Mass Number of an element is equal to the protons plus neutrons.

The element Sodium has an atomic number of 11 and an average atomic mass of 22.98 which makes the mass number 23.


An atomic number of 11 means this atom will have 11 protons.

A mass number of 23 means 23 minus 11, this atom will have 12 neutrons.

Since this atom is neutral the positive protons must be equal to the negative electrons. This atom will have Eleven electrons.

Example 1

The element sodium has 12 neutrons, 11 electrons and 11 protons. The number of electrons and protons come from the element's atomic number, which is same 11. The number of neutrons can be found by subtraction of the atomic number from sodium's atomic mass of twenty three.

Example 2

On the other hand Hydrogen has only one proton, no neutrons, and uncharged, has one electron. However note that in nature, free hydrogen is found as a diatomic molecule. Therefore, a hydrogen molecule has two protons, and 2 electrons (which form the bond between hydrogen atoms).

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