Atomic Structure

Total Questions: 39

31. The mass number of a nucleus is: [67th B.P.S.C. (Pre) 2022]

Correct Answer: (a) The sum of the numbers of neutrons and protons
Note:

 

The mass number is the sum of the total number of protons and neutrons inside a nucleus and represents its atomic mass. Therefore, the mass number equals the number of protons plus the number of neutrons.

32. The number of neutrons in the nucleus of plutonium nuclide ( 242 Pu 242 Pu) is: [66th B.P.S.C. (Pre) 2020]

Correct Answer: (b) 148
Note:

The number of neutrons in the nucleus of plutonium (242Pu^{242}\text{Pu}) is calculated by subtracting the number of protons from the mass number. 242Pu^{242}\text{Pu} has a mass number of 242 and 94 protons. Therefore, the number of neutrons is 242โˆ’94=148242 - 94 = 148.

33. The atoms in which the number of protons is the same, but the number of neutrons is different, are known as: [U.P.P.C.S. (Mains) 2009, Chhattisgarh P.C.S. (Pre) 2005, Uttarakhand U.D.A./L.D.A. (Pre) 2003]

Correct Answer: (d) Isotopes
Note:

 

The Isotopes are a set of nuclides/atoms having the same number of protons, but a different number of neutrons. In other words, the same atomic number but having different atomic mass. Each individual isotope has a separate nuclei. The Isotopes that are unstable and undergo radioactive decay are called radioisotopes.

34. Isotopes of an element differ in: [67th B.P.S.C. (Pre) 2022]

Correct Answer: (b) The mass number
Note:

The Isotopes are a set of nuclides/atoms having the same number of protons, but a different number of neutrons. In other words, the same atomic number but having different atomic mass. Each individual isotope has a separate nuclei. The Isotopes that are unstable and undergo radioactive decay are called radioisotopes.

35. Isotopes are those atoms of the same element which have: [U.P. U.D.A./L.D.A. (Pre) 2001]

Correct Answer: (b) Atomic mass is different, but the atomic number is the same
Note:

The Isotopes are a set of nuclides/atoms having the same number of protons, but a different number of neutrons. In other words, the same atomic number but having different atomic mass. Each individual isotope has a separate nuclei. The Isotopes that are unstable and undergo radioactive decay are called radioisotopes.

36. Isotopes are that nuclei of atomic nuclei in which: [41" B.P.S.C. (Pre) 1996]

Correct Answer: (b) The number of protons is the same, but the number of neutrons is different
Note:

The Isotopes are a set of nuclides/atoms having the same number of protons, but a different number of neutrons. In other words, the same atomic number but having different atomic mass. Each individual isotope has a separate nuclei. The Isotopes that are unstable and undergo radioactive decay are called radioisotopes.

37. Radioactivity is measured by: [U.P.P.S.C. (GIC) 2010]

Correct Answer: (b) Geiger Counter
Note:

The Geiger-Muller Counter also called a Geiger Counter, is an instrument used for detection and measurement of ionizing radiation. It detects radiation such as alpha particles, beta particles and gamma rays using the ionization produced in a Geiger-Muller tube, which gives its name to the instrument

38. Radioactivity was discovered by: [U.P.P.C.S. (Mains) 2003]

Correct Answer: (b) Becquerel
Note:

Radioactivity was discovered in 1896 by the French Scientist Henri Becquerel when he was working with phosphorescent materials.

39. The isoneutronic group in the following is: [R.A.S./R.T.S. (Pre) 1999]

Correct Answer: (d) 6 /14 C , 7 /15 N , 8 /16 O 6 /14 C, 7 /15 โ€‹ N, 8 /16 O
Note:

Two nuclides are isoneutronic (isotones) if they have the same neutron number NN, but a different proton number ZZ.

For example, Boron-12 and Carbon-13 nuclei both contain 7 neutrons and are thus isotones.

As per the question:

  • 614C^{14}_{6}\text{C} โ†’ 14โˆ’6=814 - 6 = 8 neutrons
  • 715N^{15}_{7}\text{N} โ†’ 15โˆ’7=815 - 7 = 8 neutrons
  • 816O^{16}_{8}\text{O} โ†’ 16โˆ’8=816 - 8 = 8 neutrons

Since the number of neutrons in all is 8, they are all isotones.