Consider the following statements regarding the discovery and properties of neutrons: 1. They were discovered by J.J. Thomson in 1897. 2. They are present in the nucleus of all atoms including hydrogen. 3. A neutron has no charge and a mass nearly equal to that of a proton. Which of the statements given above is/are correct?

The correct option is C. Explanation The neutron is a subatomic particle that, along with protons, constitutes the nucleus of an atom. Its discovery and physical properties are fundamental to understanding atomic structure and isotopes. Statement-wise Analysis: - Statement 1 is Incorrect: Neutrons were discovered by James Chadwick in 1932. J.J. Thomson is credited with the discovery of the electron in 1897 through his experiments with cathode ray tubes. - Statement 2 is Incorrect: While neutrons are present in the nuclei of almost all atoms, the most common isotope of hydrogen, Protium (¹H), consists of only one proton and one electron, with no neutrons in its nucleus. Neutrons are present in other isotopes of hydrogen, such as Deuterium and Tritium. - Statement 3 is Correct: A neutron is electrically neutral, carrying no charge. Its mass is approximately 1.6749 × 10⁻²⁷ kg, which is slightly greater than but nearly equal to the mass of a proton (1.6726 × 10⁻²⁷ kg). Key Takeaway: The neutron was discovered by James Chadwick and is present in all atomic nuclei except for the most common isotope of hydrogen (Protium).

Consider the following statements regarding the di... - NCERT Class 9 Science MCQ

The correct option is C.

Explanation

The neutron is a subatomic particle that, along with protons, constitutes the nucleus of an atom. Its discovery and physical properties are fundamental to understanding atomic structure and isotopes. Statement-wise Analysis:

Statement 1 is Incorrect: Neutrons were discovered by James Chadwick in 1932. J.J. Thomson is credited with the discovery of the electron in 1897 through his experiments with cathode ray tubes.
Statement 2 is Incorrect: While neutrons are present in the nuclei of almost all atoms, the most common isotope of hydrogen, Protium (¹H), consists of only one proton and one electron, with no neutrons in its nucleus. Neutrons are present in other isotopes of hydrogen, such as Deuterium and Tritium.
Statement 3 is Correct: A neutron is electrically neutral, carrying no charge. Its mass is approximately 1.6749 × 10⁻²⁷ kg, which is slightly greater than but nearly equal to the mass of a proton (1.6726 × 10⁻²⁷ kg).

Key Takeaway: The neutron was discovered by James Chadwick and is present in all atomic nuclei except for the most common isotope of hydrogen (Protium).

NCERT Class 9 Science — Chapter 4: Structure of the atom

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