Which of the following representations is correct for an atom X with 28 electrons and 30 neutrons?
A
\(^{58}_{28}X\)
B
\(^{30}_{28}X\)
C
\(^{28}_{30}X\)
D
\(^{58}_{30}X\)
Verified Correct Answer: A.
Physical Principles & Numerical Solution
An atom can be represented thus,
\(^{Z}_{A}X\) where Z = mass number
A = atomic number
A = number of proton = number of electrons in a free state = 28
Z = number of protons + number of neutrons = 28 + 30 = 58
\(^{58}_{28}X\)is the representation
Source: Myschool Past Questions Archive (Record #46471)