An atom has an average atomic mass of about 24.3 amu. what is the chemical
symbol for the atom? consult the periodic table.
o mg
o cr
o mn
o ca

Option (a) is the correct answer.

Explanation:

Atomic number is the sum of only total number of protons present in an element. Whereas mass number is the sum of total number of both protons and neutrons present in an element.

So, for an atom with atomic mass 24.3 amu must have an atomic number as 12.

And, according to the periodic table only magnesium is the element which has an atomic number 12. As every element has different atomic number.

Chemical symbol which represents magnesium is Mg.

Thus, we can  conclude that Mg is the chemical  symbol for the atom which has an average atomic mass of about 24.3 amu.