Chapter 4

NCERT
Class 9
Science
Solutions
14. For the following statements, write T for true and F for false.

Question:

For the following statements, write T for true and F for false.

(a) J.J. Thomson proposed that the nucleus of an atom contains only nucleus.

(b) A neutron is formed by an electron and a proton combining together. Therefore it is neutral.

(c) The mass of an electron is about 1/2000 times that of proton.

(d) An isotope of iodine is used for making tincture iodine. Which is used as a medicine

Answer:

(a) J.J. Thomson proposed the model of the atom that only contains electrons and protons and no neutrons. He made no mention of the nucleus or the nucleons. Therefore, the given statement is false.​

(b) Neutron is not formed by an electron and a proton combining together. Neutron is an independent sub-atomic particle like electron and proton.​ Therefore, the given statement is false.​

(c) The mass of an electron is 9.109 × 10 − 31kg (considered to be negligible) whereas the mass of a proton is 1.6726 ×10 − 27kg  which is approximately 2000 times the mass of an electron.​ Therefore, the given statement is true.​

(d) Tincture iodine is an antiseptic that usually contains 2–7% elemental I-127 dissolved in a mixture of ethanol and water. ​Therefore, the given statement is true.​

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