How many electrons would it take to equal the mass of a helium nucleus?

Hint: The nucleus of the atom contains the protons and the neutrons. So the total mass of the nucleus will be determined by the mass of protons and neutrons. The atomic number of helium is 2.

Complete answer:
As we know that the atom is the simplest unit which combines with the other atom to form a molecule. The atom contains three subatomic particles proton, neutron and electron. The center of the atom is known as the nucleus. The proton is the positively charged species, neutron is the neutral charge species and the electrons are the negatively charged species. The nucleus of the atom contains protons and neutrons. The electrons surround the nucleus of the atom in a circular orbit.
Helium is the chemical element with the symbol He. It is present in group 18 which is known as noble gases. The helium atom is present in s-block and in period 1. The atomic number of helium is 2 and the electronic configuration of the helium is $1{s^2}$.
The mass of the proton is $1.6726219 \times {10^{ - 27}}kg$. The mass of a neutron is $1.67492749804 \times {10^{ - 27}}kg$. As, protons and neutrons both are present in the nucleus. The number of protons in a helium atom is 2 and the number of neutrons is 2. The total mass will be $6.64 \times {10^{ - 27}}kg$ which relates to the mass of ${}^4He$.
The electronic mass is $9.11 \times {10^{ - 31}}kg$
To calculate the number of electrons, divide the total mass of the nucleus with the electronic mass.
$\Rightarrow \dfrac{{6.64 \times {{10}^{ - 27}}kg}}{{9.11 \times {{10}^{ - 31}}kg}}$
$\Rightarrow 7.28869 \times {10^{ - 59}}$

Therefore, it will take $7.28869 \times {10^{ - 59}}$ number of electrons to equal the mass of a helium nucleus.

Note: The atomic number of the atom is equal to the number of electrons and the protons. The sum of protons and the neutrons is equal to the mass number, therefore the helium atom with mass number 4 is the isotope ${}^4He$.