Answer:
Option B is correct.
4
Explanation:
We know that an atom consist of electron, protons and neutrons. Protons and neutrons are present with in nucleus while the electrons are present out side the nucleus.
All these three subatomic particles construct an atom. A neutral atom have equal number of proton and electron. In other words we can say that negative and positive charges are equal in magnitude and cancel the each other. For example, if neutral atom has 6 protons than it must have 6 electrons. The sum of neutrons and protons is the mass number of an atom while the number of protons are number of electrons is the atomic number of an atom.
In given problem we are given with 2 neutrons of helium. We know that the atomic number of He is 2. Thus Mass number of He is,
Number of neutrons + number of proton
2 + 2 = 4
Thus, option B is correct.
Answer:
The approximate mass of beryllium is 9.0045 u.
Explanation:
Given data:
mass of helium= 4.002 u
mass of beryllium which is 2.25 times of mass of helium= ?
Solution:
we will multiply the mass of helium with 2.25 times,
4.002 u × 2.25 = 9.0045 u
so the mass of beryllium atom would be 9.0045 u.
