Which one of the following statements is correct?
- (a)A neutron is formed by combination of an electron and a proton. Therefore, it is neutral
- (b)The mass of an electron is about 1/2000 times that of a proton
- (c)An isotope of cobalt is used in the treatment of goiter
- (d)J. J. Thomson proposed that the nucleus of an atom contains only neutrons
Correct — B, the electron's mass. An electron's mass — about 1/1836 of a proton's — is roughly 1/2000 that of a proton, so it is nearly negligible next to the nucleons. Statement (b) is therefore the one that is correct.
- (a)A neutron is formed by combination of an electron and a proton. Therefore, it is neutral — A neutron is a fundamental nucleon, not literally an electron stuck onto a proton; describing it that way is incorrect, even though its net charge is zero.
- (c)An isotope of cobalt is used in the treatment of goiter — Cobalt-60 is used to treat cancer by radiotherapy, not goitre; goitre and thyroid disorders are treated with Iodine-131.
- (d)J. J. Thomson proposed that the nucleus of an atom contains only neutrons — Thomson proposed the plum-pudding model — electrons embedded in a positive sphere; he never said the nucleus holds only neutrons, and the neutron was found only later, by Chadwick in 1932.
An atom has a tiny dense nucleus of protons and neutrons, with electrons around it. A proton and a neutron each weigh about one atomic mass unit, while the electron is roughly 1836 times lighter.
Each wrong option hides a familiar mistake — a false model of the neutron, a swapped medical isotope, or a mis-attributed atomic model. Only the electron-mass figure survives scrutiny.
- An electron's mass is about 1/1836 (roughly 1/2000) that of a proton.
- A proton and a neutron each have a mass of about one atomic mass unit.
- Cobalt-60 is used in cancer radiotherapy; Iodine-131 is used for the thyroid and goitre.
- J. J. Thomson discovered the electron in 1897 and gave the plum-pudding model.
- Confusing Cobalt-60 (cancer) with Iodine-131 (thyroid and goitre).
- Treating the neutron as a bound electron-proton pair.
A 'which statement is correct' item mixing particle masses, medical isotopes and atomic-model attributions.
No directly related past PYQ was found.
- practice — not a real PYQ
Which radioisotope is commonly used in the treatment of goitre and other thyroid disorders?
- (a)Cobalt-60
- (b)Iodine-131
- (c)Carbon-14
- (d)Uranium-235
Answer(b) Iodine-131 — it is taken up by the thyroid gland.
- practice — not a real PYQ
The mass of a proton is approximately how many times that of an electron?
- (a)200
- (b)1836
- (c)92
- (d)6
Answer(b) About 1836 times.