Question

An ion X2+ contains 18 electrons and 20 neutrons. Calculate the atomic number and mass number of element X,
Name the element

Answer 1

atomic number =20(18 electrons +2 valency)
mass number=40
the element is calcium(Ca)

Answer 2

Answer: Atomic number = 20, mass number = 40 and element is Calcium

Explanation: Atomic number is equal to the number of protons.

Mass number is the sum of number of neutrons and number of protons.

For ionic species, number of protons = no of electrons+ charge (with sign)= 18+(+2)= 20.

Thus atomic number = 20

Mass number =  number of neutrons + number of protons = 20+20= 40

the atomic number is specific to an element, and the element with atomic number 20 is calcium. The representation is $_{20}^{40}\textrm {Ca}$