Question

Which of the following combination represents an element with a net charge of +1 with a mass number of 75?

• A. 40 neutrons, 34 protons, 35 electrons
• B. 39 neutrons, 36 protons, 34 electrons
• C. 40 neutrons, 35 protons, 34 electrons
• D. 37 neutrons, 38 protons, 39 electrons

Answer 1

Answer: (C)

40 neutrons, 35 protons, 34 electrons

Mass number= Number of protons + Number of neutrons

$\Rightarrow 35+40=75$

Number of proton= Number of electron in neutral molecule

This element has net positive charge as $+1$. Hence there should be $1e^{-}$ less than proton. There are $35$ protons $\therefore$ electrons=$34$