Atoms and Nuclei MCQs for NEET

The entire positive charge and most of the mass of the atom is concentrated in a small space known as the nucleus. The nucleus consists of protons and neutrons and together there are known as the nucleons. Following are a few important terms related to the nucleus:

• Atomic Number
• Mass Number
• Nuclear Density
• Isotopes
• Isobars
• Isotones
• Isomers

Question and Answer

1. Which of the following should we consider to explain the fine structure of the spectrum of hydrogen?

1. The presence of neutrons in the nucleus
2. Orbital Angular Momentum
3. Infinite size of the nucleus
4. Spin angular Momentum

Answer: (d) Spin Angular Momentum

2. Which of the following statements is true about Bohr’s atomic model?

1. The electron can only move in particular orbits only
2. An electron radiates energy only when it jumps to another orbit
3. An atom consists of a positively charged nucleus
4. All of the above

Answer: (d) All of the above

3. If the radius of Bohr’s first orbit is a₀, what is the radius of the nth orbit?

1. na₀
2. a₀/n
3. n²a₀
4. a₀/n²

Answer: (c) n²a₀

4. Of the various series of the hydrogen spectrum, which of the following lies wholly in the ultraviolet region?

1. Balmer Series
2. Paschen Series
3. Brackett series
4. Lyman Series

Answer: (d) Lyman Series

5. In Bohr’s model, if the radius of the first orbit is r₀, what is the radius of the third orbit?

1. 3r₀
2. 9r₀
3. r₀/9
4. r₀

Answer: (b) 9r₀

6. What is the energy needed to ionize H-atom from its second excited state if the energy of the ground state of H-atom is 13.6 eV?

1. 3.4 eV
2. 1.51 eV
3. 12.1 eV
4. 13.6 eV

Answer: (b) 1.51 eV

7. Which of the following regions does X-ray lie between?

1. visible and ultraviolet regions
2. short radio waves and long radio waves
3. short radio waves and visible region
4. gamma rays and ultraviolet region

Answer: (d) gamma rays and ultraviolet region

8. Which of the following is a correct statement?

1. Equal fractions disintegrate in equal intervals of time.
2. The rate of disintegration is directly proportional to the number of atoms present in the sample at that instant.
3. A radioactive sample takes an infinite time to disintegrate completely
4. All of the above

Answer: (d) All of the above

9. Which of the following is true about gamma rays?

1. Gamma rays are uncharged high energy rays coming from the outer space
2. Gamma rays are high energy rays emitted by radioactive elements
3. Gamma rays are charged particles emitted by radioactive elements
4. Gamma rays are charged high energy rays coming from the outer space

Answer: (b) Gamma rays are high energy rays emitted by radioactive elements

10. How many numbers of spectral lines are observed when hydrogen atoms are excited from ground state to the state of principal quantum number 4?

1. 2
2. 3
3. 5
4. 6

Answer: (d) 6

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