The greatest composition by mass in an atom of 17/8 O is due to the total mass of its

A) electrons

B) neutrons

C) positrons

D) protons

The largest mass of an atom is occupied by its Nucleus in which the Neutrons have the biggest size but have no charge, then it is the Protons and the Electrons have almost negligible mass.

Answer is B) - neutrons.

Both protons and neutrons contribute to the mass of an atom. But ₈¹⁷O atom has atomic number as 8. Hence, number of protons is 8. Atomic mass of the given atom is 17.

Atomic mass = number of protons + number of neutrons

Hence, number of neutrons in the given atom is 17 - 8 = 9.

So, the number of neutrons is greater than the number of protons. Hence the greatest composition of ₈¹⁷O atom is neutrons by mass.