Question

Calculate the approximate atomic mass of oxygen atom $168O$ in the order of ${10}^{-26}$.

• A. 2.672

Answer 1

The correct option is A 2.672
Given:
Oxygen, $168O$
Mass number, A = 16
Atomic number, Z = 8
In an atom, the number of protons = the number of electrons = Atomic number = Z = 8
Number of neutrons = A - Z = 16 - 8 = 8
Mass of a neutron, $m_n$ $\approx$ Mass of a proton, $m_p$ = $1.67\times {10}^{-27}kg$ ---- (1)
Mass of an atom, M = $Z{m}_p+(A-Z)m_n$
From (1):
M = $(Z+A-Z)m_p=A{m}_p$
$⟹$ M = $16\times 1.67\times {10}^{-27}kg$
$⟹$ M $\approx 2.672\times {10}^{-26}kg$