Question

The element selenium has the symbol ${}_{34}{}^{79}\mathrm{Se}$.Calculate the number of each subatomic particles in selenide anion Se^2-

Answer 1

• Protons, electrons and neutrons are known as subatomic particles.
• Given the atomic number of Se is 34 and a neutral Se atom will have 34 electrons.
• Selenium atom on gaining of 2 electrons will become Se^2- .
• Hence, the total number of electrons in Se^2- =(34+2)=36.
• Atomic number/number of protons does not change for a particular chemical atom and hence the number of protons=34
• Mass number= 79=sum of protons and neutrons; number of neutrons = (79-34)=45