Chemistry - Atomic Structure Question with Solution | TestHub

The notation for an atom is ${}_Z^A\mathrm{X}$, where:

$A$ = Mass number (number of protons + neutrons)

$Z$ = Atomic number (number of protons)

For ${}_{92}^{238}\mathrm{U}$:

$Z=92$, so the number of protons is 92.

$A=238$, so the number of nucleons (protons + neutrons) is 238.

Number of neutrons = $A-Z=238-92=146$.

Electrons are NOT found in the nucleus. Therefore, the number of electrons in the nucleus is zero.

Matching the lists:

(P) No. of electrons in nucleus of ${}_{92}^{238}\mathrm{U}$$\to$ (4) Zero

(Q) No. of protons in nucleus of ${}_{92}^{238}\mathrm{U}$$\to$ (3) 92

(R) No. of neutrons in nucleus of ${}_{92}^{238}\mathrm{U}$$\to$ (1) 146

(S) No. of nucleons in nucleus of ${}_{92}^{238}\mathrm{U}$$\to$ (2) 238

The correct match is P-4, Q-3, R-1, S-2.

The final answer is $\boxed{B}$