Question

Write the number of neutrons and the symbol of an element
which has mass number 40 and atomic number 20.

Answer 1

In the modern periodic table, the elements are listed in order of increasing atomic number. The atomic number is the number of protons in the nucleus of an atom. The number of protons define the identity of an element (i.e., an element with 6 protons is a carbon atom, no matter how many neutrons may be present). The number of protons determines how many electrons surround the nucleus, and it is the arrangement of these electrons that determines most of the chemical behavior of an element.

Answer 2

Number of Protons = atomic number = 20.

Therefore, number of protons = 20.

Number of electrons = number of protons = 20.

Number of neutrons = Mass number - number of protons = 40-20 = 20.

Calcium (Ca)