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

Consider the following applications of isotopes: 1. An isotope of Uranium is used as fuel in nuclear reactors. 2. An isotope of Cobalt is used in the treatment of goitre. 3. An isotope of Iodine is used in the treatment of cancer.

Match List I with List II and select the correct answer using the code given below: List I | List II A. Uranium | 1. Treatment of Goitre B. Cobalt | 2. Treatment of Cancer C. Iodine | 3. Fuel in Nuclear Reactors

The 'plum pudding' model of the atom was proposed by:

What determines the atomic number of an atom?

Which of the following statements is NOT correct regarding the structure of an atom?

Consider the following statements about the 'Canal Rays': 1. They were discovered by E. Goldstein. 2. They are negatively charged radiations. 3. Their discovery led to the identification of the electron.

Which of the following elements has a valency of zero?

Who was the first scientist to propose a model for the structure of an atom?

Canal rays are a stream of:

According to electromagnetic theory, what is the primary consequence of an electron undergoing acceleration in a circular orbit, which became a drawback for Rutherford's model?

With reference to the discovery of sub-atomic particles, consider the following statements: 1. The presence of charged particles in an atom was revealed by the study of static electricity and conduction conditions. 2. E. Goldstein discovered the electron before the identification of canal rays. 3. Canal rays are negatively charged radiations. Which of the statements given above is/are correct?

Consider the following statements regarding the mass of an atom: 1. The mass of an electron is considered negligible. 2. The mass of an atom is practically due to electrons and protons alone. 3. The mass of a proton is taken as one unit.

Which isotope is used as a fuel in nuclear reactors?

With reference to 'Valency', consider the following statements: 1. It is the combining capacity of the atoms of elements. 2. Atoms react to achieve a duplet in the outermost shell in all cases. 3. If the outermost shell has 8 electrons, the valency is 8. Which of the statements given above is/are correct?

With reference to Isobars, consider the following statements: 1. They are atoms of different elements with different atomic numbers. 2. They possess different mass numbers. 3. Calcium and Argon are examples of isobars.

Consider the following statements regarding the calculation of valency: 1. For elements like hydrogen and sodium, valency is equal to the number of electrons in the outermost shell. 2. For elements like fluorine and oxygen, valency is equal to the number of valence electrons plus two. 3. Magnesium has a valency of 2 because it loses two electrons to complete its octet. Which of the statements given above is/are correct?

Consider the following statements regarding the discovery of the nucleus: 1. It was discovered by J.J. Thomson. 2. The discovery resulted from the alpha-particle scattering experiment. 3. The experiment involved firing alpha particles at a thin gold foil.

Why do inert gases like Helium and Neon show little chemical activity?

In Rutherford's alpha-particle scattering experiment, why were large deflections not anticipated based on the then-prevailing Thomson model?

With reference to Atomic Number and Mass Number, consider the following statements: 1. Atomic number is defined as the total number of neutrons present in the nucleus. 2. Mass number is the sum of the total number of protons and neutrons in an atom. 3. Elements are defined by the number of protons they possess. Which of the statements given above is/are correct?

With reference to Neils Bohr’s model of the atom, consider the following statements: 1. Only certain special orbits known as discrete orbits of electrons are allowed inside the atom. 2. Electrons radiate energy continuously while revolving in discrete orbits. 3. These discrete orbits are called energy levels. Which of the statements given above is/are correct?

Which of the following observations were made during Rutherford’s alpha-particle scattering experiment? 1. Most of the alpha particles were deflected back by 180 degrees. 2. Some alpha particles were deflected by small angles. 3. One out of every 12,000 particles appeared to rebound. Select the correct answer using the code given below:

Based on the alpha-particle scattering experiment, Rutherford concluded that: 1. Most of the space inside the atom is empty. 2. The positive charge of the atom occupies a very large volume. 3. The mass of the atom is distributed evenly throughout its volume. Which of the statements given above is/are correct?

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?

Consider the following statements about Isotopes: 1. They are atoms of the same element having the same atomic number but different mass numbers. 2. The chemical properties of isotopes are different, but their physical properties are similar. 3. A mixture of isotopes is considered a pure substance. Which of the statements given above is/are correct?

Which of the following statements best explains why atoms are electrically neutral?

Consider the following statements about the isotopes of Hydrogen: 1. Protium has no neutrons. 2. Deuterium has two neutrons. 3. Tritium has one neutron.

With reference to the stability of an atom, how did Bohr’s model improve upon Rutherford’s model?

Consider the following statements regarding the valency of Nitrogen and Phosphorus: 1. Nitrogen has 3 valence electrons and a valency of 5. 2. Phosphorus has 5 valence electrons and can exhibit valencies of 3 and 5. 3. Nitrogen and Phosphorus belong to different groups in the periodic table.

With reference to the definition of an element, consider the following statements: 1. Elements are defined by the number of protons they possess. 2. Atoms of a given element can have different numbers of protons. 3. The atomic number is characteristic of a particular element.

Consider the following statements regarding the physical and chemical properties of isotopes: 1. Isotopes of an element have different chemical properties. 2. Isotopes of an element have different physical properties. 3. The difference in mass numbers leads to differences in physical properties.

Which sub-atomic particle was identified by J. Chadwick in 1932?

Why is the mass of an electron not included in the calculation of the mass number of an atom?

The mass of a proton is approximately how many times that of an electron?

Which isotope is used in the treatment of goitre?

What is the maximum number of electrons that can be accommodated in the outermost orbit of an atom?

Match List I with List II and select the correct answer using the code given below: List I | List II A. J.J. Thomson | 1. Discovery of Canal Rays B. E. Goldstein | 2. Discovery of Electron C. E. Rutherford | 3. Discovery of Neutron D. J. Chadwick | 4. Discovery of Nucleus

Which of the following pairs represents Isobars?

In the context of atomic structure, what are 'Nucleons'?

Which scientist was awarded the Nobel Prize in Physics in 1906 for the discovery of electrons?

In Rutherford's experiment, alpha particles are actually:

Consider the following statements regarding the properties of protons and electrons as described in the early atomic theories: 1. The mass of a proton is approximately 2000 times that of an electron. 2. The charge of a proton is significantly larger than that of an electron. 3. Protons can be easily removed from the interior of an atom compared to electrons. Which of the statements given above is/are correct?

What term is used for atoms of different elements with different atomic numbers but the same mass number?

Consider the following statements regarding the distribution of electrons in the first eighteen elements: 1. The K-shell can accommodate a maximum of 8 electrons. 2. The L-shell can accommodate a maximum of 8 electrons. 3. Electrons are not accommodated in a given shell unless the inner shells are filled.