Chapter 4: Structure of the Atom — Online MCQ Test
SCIENCE · CLASS 9th · Karnataka State Board
Practice Chapter 4: Structure of the Atom with a free chapter-wise online MCQ test.
This chapter covers: This chapter details charged particles Thomson Rutherford Bohr atomic models subatomic particles atomic number mass number isotopes and isobars..
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Chapter 4: Structure of the Atom — Important Questions & Answers
Who discovered the electron?
- A. J. J. Thomson
- B. Ernest Rutherford
- C. Niels Bohr
- D. James Chadwick
Answer: A. J. J. Thomson
J. J. Thomson discovered the electron through cathode ray experiments. This was one of the first proofs that atoms contain smaller charged particles.
J. J. Thomson discovered the electron through cathode ray experiments. This was one of the first proofs that atoms contain smaller charged particles.
What is the charge of a proton?
- A. Negative
- B. No charge
- C. Positive
- D. Depends on the atom
Answer: C. Positive
A proton carries a positive charge. It is located in the nucleus of an atom.
A proton carries a positive charge. It is located in the nucleus of an atom.
Which statement is true about Rutherford's atomic model?
- A. Electrons are embedded in a positively charged sphere
- B. Most of the atom is empty space
- C. Electrons have fixed circular orbits with fixed energies
- D. The atom is indivisible
Answer: B. Most of the atom is empty space
Rutherford's gold foil experiment showed that most of the atom is empty space. A small, dense, positively charged nucleus is present at the center.
Rutherford's gold foil experiment showed that most of the atom is empty space. A small, dense, positively charged nucleus is present at the center.
An element X has 12 electrons, 12 protons, and 13 neutrons. What is its mass number?
- A. 12
- B. 13
- C. 24
- D. 25
Answer: D. 25
Mass number = number of protons + number of neutrons = 12 + 13 = 25. Electrons are not counted in mass number.
Mass number = number of protons + number of neutrons = 12 + 13 = 25. Electrons are not counted in mass number.
Which statement best explains why isotopes of an element have nearly the same chemical properties?
- A. They have the same number of neutrons
- B. They have the same number of protons and electrons
- C. They have the same mass number
- D. They occupy the same position in the periodic table because of different atomic numbers
Answer: B. They have the same number of protons and electrons
Chemical properties depend mainly on the electronic configuration, which is determined by the number of protons in a neutral atom. Isotopes have the same atomic number, so their chemical properties are nearly the same.
Chemical properties depend mainly on the electronic configuration, which is determined by the number of protons in a neutral atom. Isotopes have the same atomic number, so their chemical properties are nearly the same.