Question

An atom has mass number 23 and atomic number 11.

a) How many electrons are revolving around the nucleus?
b) How many electron shells are there in the atom?

Answer 1

Given:
- Mass number of atom = 23
- Atomic number of atom = 11

As, the number of electrons in an atom is equal to an atomic number of the element.

So, number of electrons = 11

Secondly , number of protons are equal to number of electrons.

So, number of protons = 11

And number of neutrons = mass number - atomic number = 23−11 = 12

So, number of neutrons = 12

Thus , the atom contains 11 protons, 11 electrons, 12 neutrons.

Answer 2

A): The closest orbital to the nucleus, called the 1s orbital, can hold up to two electrons. This orbital is equivalent to the innermost electron shell of the Bohr model of the atom. It is called the 1s orbital because it is spherical around the nucleus. The 1s orbital is always filled before any other orbital.