Question

The atomic number of an element is 92 and the mass number is 238. Calculate the number of subatomic particles of the atom.

Answer 1

Hint: According to the question we know the atomic number. Therefore, with the help of the atomic number we can find the number of electrons and a corresponding number of protons. We also know the atomic mass. Therefore, with the help of atomic mass, we can find the number of neutrons.

Formula used: The number of neutrons$ = $Atomic mass number-Atomic number

Complete step by step solution:
According to physical sciences, subatomic particles are smaller than atoms. There are three main types of subatomic particles.
1. Protons
2. Electrons
3. Neutrons
Protons are particles that are positively charged and they are also located in the nucleus. Protons, including neutrons, give the atom mass. Protons and neutrons are not involved in the chemical reaction. The number of protons that an atom has is called the atomic number. With the use of the atomic number, we can determine the identity of the atom.
Electrons are particles that are negatively charged and they are found in shells that surround the nucleus. They have negligible mass, but in chemical reactions, they play an important role. The first shell of electrons could accommodate two electrons. Additional shells of electrons will contain up to eight electrons for relevant atoms.
Neutrons are particles that are neutrally charged particles contained in the nucleus of the atom. Neutrons give the atomic mass but they are not involved in chemical reactions.
Atomic number of a given element is 92, so elements have 92 electrons and corresponding 92 protons.
The atomic mass of a given compound is $238$
So, the number of neutrons $ = $Atomic mass number-Atomic number
$ = $$238 - 92$
$ = $$146$

Hence, the element has $92$ electrons, $92$ protons and $146$ neutrons.

Note: A property related to an atom’s mass number is its atomic mass. The atomic mass of a single atom is its total mass and is expressed in atomic mass units or amu. By definition, an atom of carbon with six neutrons, carbon-$12$, has an atomic mass of $12$ amu. Other atoms do not have a round number of atomic mass so carbon-$12$, is selected as a reference.