# Calculate the number of electrons, protons and neutrons in `Na_11^23` . When two numbers are present along with the symbol of an element, one of them (usually the number on top or the superscript) is the mass number, while the other (usually the number at the bottom or the subscript) is the atomic number.

These two terms are used to characterize...

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When two numbers are present along with the symbol of an element, one of them (usually the number on top or the superscript) is the mass number, while the other (usually the number at the bottom or the subscript) is the atomic number.

These two terms are used to characterize an element and are defined in terms of the sub-atomic particles (protons, neutrons and electrons). The atomic number of an element is the same as the number of protons in an atom of that element.

That is, atomic number = number of protons = 11

Similarly, mass number is the sum total of protons and neutrons. That is,

mass number = number of protons + number of neutrons

or, number of neutrons = mass number - number of protons

= mass number - atomic number = 23 - 11 = 12.

For an atom in the ground state, number of protons = number of electrons = 11.

Hope this helps.

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