An atom has a mass number of 25 and 13 neutrons. What is the atomic number of this atom?

1 Answer
Meave60
May 13, 2018

The atomic number is #12#, which is the atomic number for magnesium.

Explanation:

The mass number of an isotope is the sum of the protons and neutrons in its atomic nuclei.

If we know the mass number #("A")# and the number of neutrons #("N")#, we can calculate the atomic number #("Z")# by subtracting the number of neutrons from the mass number.

#"A"-"N"="Z"#

#25-13=12#

The atomic number of the element is #12#. Atomic number is the number of protons in the nuclei of all atoms of an element. The element with the atomic number 12 is magnesium.

This is #""^25"Mg"#, or magnesium-25, which can be abbreviated as Mg-25.

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