Helium is the lightest noble gas and the second most abundant element (after hydrogen) in the universe. the mass of a helium−4 atom is 6.64648 × 10−24g, and each of its two electrons has a mass of 9.10939 × 10−28g. what fraction of this atom's mass is contributed by its nucleus?

The fraction of atom's mass contributed by nucleus is 0.99

Explanation:

Nucleons are defined as the sub-atomic particles which are present in the nucleus of an atom. Nucleons are protons and neutrons.

The isotopic symbol of Helium-4 atom is

Number of electrons = 2

Number of protons = 2

Number of neutrons = 4 - 2 = 2

We are given:

Mass of He-4 atom =

Mass of 1 electron =

Calculating the mass contributed by the nucleus =

Mass of the nucleus of He-4 atom =

To calculate the fraction of atom's mass contributed by the nucleus, we use the equation:

Putting values in above equation, we get:

Hence, the fraction of atom's mass contributed by nucleus is 0.99

the formula mass of a molecule or a compound is the sum of the atomic weights of the atoms in its empirical formula

(that's what i know about formula mass)