Atoms and Nuclei MCQ: Introduction and Sample Questions

Ans. b) Spin-dependent and have no non-central part

Explanation: Nuclear forces are spin-dependent and do not have a non-central part. It is the strongest force of attraction. It can be found in between the nucleons. The force lies between nucleons that have parallel spin. Therefore it has greater forces between nucleons with antiparallel spin. The term non-central is used because the nucleons are spherically asymmetric in the structure.

Ans. b) KNO₃

Explanation: Potassium Nitrate is a chemical element. It is basically a crystalline salt containing strong oxidizing powers. They are used to manufacture different components. For example fertilizer, gunpowder, and medicines. Potassium nitrate is inorganic in nature. The chemical formula of Potassium Nitrate is KNO₃. In the formula, K stands for Potassium and NO₃ means Nitrate.

Ans. a) 2

Explanation: The values are given.

Atomic Mass / Molar mass of Sodium = 23 

To calculate the number of moles in 46 g of Na

Formula (No. of moles) = Given Mass/ Molar Mass

By putting value in each place, 

No. of Moles = 46/23

Therefore, No. of Moles = 2

Ans. d) BiPO₄

Explanation: The real or correct chemical formula here is BiPO₄. By balancing the charge on the atoms, one may get the subscripts in a chemical formula. Bismuth orthophosphate is a chemical compound that contains bismuth. The valencies of all the elements are not balanced compared to the other compounds here.

Ans. a) n = N / N_o

Explanation: The example of the correct relation between Avogadro’s number and the number of particles and moles is n = N / No. Here the symbol of No represents Avogadro's number, n represents the number of miles and N is the number of particles present. There are 6.022 × 10²³ molecules per gram-mole of material, often known as the Avogadro constant, which is the molecular weight in grams. For instance, oxygen has a molecular weight of 32.00. 6.02214076 × 10²³ molecules make up one gram-mole of oxygen, which has a mass of 32.00 grams.

Ans. c) 54.207 × 10²³

Explanation: The mass of CaCO₃ is given = 300g

So, Molar mass of CaCO₃ = 40 + 12 + (3 x 16)

=100 g mol^-1

Now, the number of moles of CaCO₃ = mass / molar mass

= 300g/ 100 g mol^-1

= 3 moles

Now, the number of oxygen atoms in CaCO₃ = 3

Then, Number of moles of oxygen atoms = 3 x 3 moles = 9 moles

Then, 1 mole of oxygen contains 6.022 x 10²³ atoms of oxygen.

Therefore , 9 moles of oxygen contains = 9 x 6.022 x 10²³ atoms

= 54.207 x 10²³ oxygen atoms

Hence, the number of Oxygen atoms present in the 300 gm of CaCO₃ is 54.207 x 10²³.

Ans. c ) 2, 8, 2

Explanation: The number of electrons and the atomic number present in the Magnesium atom is 12.

So, the electronic configuration is 2, 8, 2

= 2 + 8 + 2.

Here, the maximum no. of electrons present in the K shell is 2 and the maximum no. of electrons present in the L shell is 8.

Ans. (b) 81 u

Explanation: Atomic mass of Zn = 65u 

The atomic mass of O = 16 u

So, calculate the formula unit masses of them

ZnO = Zn + O

ZnO = (65 + 16) u 

= 81u

Therefore, the formula mass unit of ZnO is 81 u.

Ans. c) Isotones

Explanation: Isotones are those nuclei that contain the same number of neutrons whereas the atomic numbers and mass numbers are different. This can be understood with the help of examples. 17Cl37 and 19k39 are two isotones. Both of them contain an equal number of neutrons. 

(Chlorine = 37-17=20 , Potassium=39-19=20.)

Ans. d) Chemical Property

Explanation: The property of an atom that stands the same in an isotope. This is because

the electronic configuration of the isotope is the same. The numbers of electrons and the number of protons are equal. Therefore, the chemical properties of the atom depend on the electrons and protons of an atom. Neutrons occupy the whole mass of the atom.

Ans. d) Neutrons

Explanation: The chemical properties of the nucleus of an atom directly depends upon the number of electrons. The electrons revolve around the nucleus and proton. The numbers of electrons and neutrons should be equal so that the balance can be maintained. Neutrons are neutral with nature. It does not contain a positive charge or a negative charge. So, the chemical properties will not be changed and the atom will gain weight only.

Ans: c) Lighter Nuclei

Explanation: In the process of nuclear fusion, more than two lighter nuclei combine together to form a heavy as well as stable nucleus. The process of nuclear fusion can occur only at extremely high temperatures and pressures. The lighter nuclei will collide early than the heavy nuclei. The weight of the nuclei affects the process of nuclear fusion.