Answer: Calcium
Explanation: As the element contains 20 electrons and 20 protons, it contains equal number of positive and negative charges, and thus it is a neutral atom.
Atomic number of an element = number of protons = number of electrons = 20
Thus the element is Ca with atomic number 20.
Mass number of an element = number of electrons + number of neutrons= 20+21= 41
Thus the representation of the element is: [tex]_Z^A\textrm{X}[/tex]
Where X = chemical symbol
A = mass number
Z = atomic number
Thus the representation is [tex]_{20}^{41}\textrm{Ca}[/tex]
