Question

An element has 20 electrons and 20 neutrons. it is electrically neutral

The mass number of an element is

Answer 1

Mass number {A} - Together, the number of protons or electrons and the number of neutrons determine an element's mass number

• Mass number = total number of electrons or proton + the total number of neutrons
• It is also called the atomic mass number.
• As both protons and neutrons are present in the nucleus of an atom, they are together called nucleons

Thus, the mass number of element = 20 protons + 20 neutron = 40