Q91. The nucleus of an atom consists of which of the following subatomic particles?
Basics of Everyday Science: RAS Prelims MCQs
200 RAS Prelims MCQs on the basics of everyday science test the scientific method, the laws of motion, chemical bonding and the cell theory. The questions use daily-life examples, such as the recoil of a gun and the orbit of a satellite, and the explanations give the principle behind each example so that you can reason out similar questions.
Practice questions based on the RPSC RAS Prelims syllabus. They follow the exam pattern but are not past-paper questions.
Showing 91–100 of 200 questions
Q92. Consider the following statements regarding the electron:
I. It has a negative electrical charge.
II. Its mass is approximately 1/1836 that of a proton.
III. It resides strictly within the nucleus of an atom.
Which of the above statement(s) is/are correct?
I. It has a negative electrical charge.
II. Its mass is approximately 1/1836 that of a proton.
III. It resides strictly within the nucleus of an atom.
Which of the above statement(s) is/are correct?
Explanation
Electrons are fundamental subatomic particles with a negative charge. Their mass is extremely small, approximately one eighteen-hundred-thirty-sixth that of a proton. Crucially, electrons do not reside within the nucleus; instead, they are found in the space surrounding the nucleus, organized into energy levels. This external positioning is essential for chemical bonding and electrical conductivity in materials.
Q93. The atomic number of an element represents the total number of:
Explanation
The atomic number is a fundamental property of an element that defines its identity. It represents the total number of protons found in the nucleus of every atom belonging to that element. In a neutral atom, the atomic number also equals the number of electrons. Because the number of protons determines the chemical behavior, no two different elements share the same atomic number.
Q94. Atoms of the same element that have the same atomic number but different mass numbers are called:
Explanation
Isotopes are variants of a particular chemical element that have the same number of protons and thus the same atomic number. However, they differ in the number of neutrons in their nuclei, resulting in different mass numbers. While isotopes of an element share almost identical chemical properties, they may exhibit different physical properties and varying levels of stability or radioactive decay.
Q95. Isobars are atoms of different elements that possess:
Explanation
Isobars are atoms of different chemical elements that possess the same mass number but have different atomic numbers. This means they have the same total number of nucleons (protons plus neutrons) in their nuclei, but the specific ratio of protons to neutrons varies. Because they have different atomic numbers, isobars belong to different elements and exhibit distinct chemical and physical properties.
Q96. Which scientist proposed the planetary model of the atom, where electrons revolve in discrete circular orbits around the nucleus?
Explanation
Niels Bohr proposed a revolutionary atomic model in 1913, often described as the planetary model. He suggested that electrons revolve around the nucleus in specific, discrete circular orbits with fixed energy levels. In this model, electrons can only exist in these allowed orbits and can jump between them by absorbing or emitting energy, explaining the unique spectral lines observed in hydrogen atoms.
Q97. Ernest Rutherford’s gold foil experiment led to the discovery of the:
Explanation
Ernest Rutherford’s famous gold foil experiment involved firing alpha particles at a thin sheet of gold. While most particles passed through, some were deflected at large angles. This unexpected result led to the conclusion that atoms are mostly empty space, with their positive charge and most of their mass concentrated in a tiny, dense central region which Rutherford named the atomic nucleus.
Q98. Arrange the following atomic models in chronological order of their proposal:
I. Bohr’s model
II. Dalton’s solid sphere model
III. Thomson’s plum pudding model
IV. Rutherford’s nuclear model
Which of the following is the correct order?
I. Bohr’s model
II. Dalton’s solid sphere model
III. Thomson’s plum pudding model
IV. Rutherford’s nuclear model
Which of the following is the correct order?
Explanation
The understanding of atomic structure evolved through several key models. John Dalton first proposed the solid sphere model in the early eighteen-hundreds. J.J. Thomson followed with the "plum pudding" model after discovering the electron. Ernest Rutherford then introduced the nuclear model based on his scattering experiments. Finally, Niels Bohr refined this by adding quantized electron orbits, creating the modern planetary model.
Q99. The combining capacity of an element with other elements is fundamentally determined by its:
Explanation
Valency is the measure of an element’s combining capacity with other atoms when forming chemical compounds or molecules. It is fundamentally determined by the number of electrons in the atom’s outermost shell, known as valence electrons. Atoms tend to gain, lose, or share these electrons to achieve a stable electronic configuration, typically resembling that of the nearest noble gas in the periodic table.
Q100. In the modern periodic table, elements are arranged in increasing order of their:
Explanation
The modern periodic table organizes chemical elements based on their increasing atomic number, which is the number of protons in an atom’s nucleus. This arrangement, established by Henry Moseley, replaced earlier versions based on atomic mass. By using atomic numbers, elements with similar electronic configurations and chemical properties fall into the same vertical columns, known as groups, revealing clear periodic trends.Answer key for these questions
| Q | Correct answer |
|---|---|
| 91 | (d) Protons and neutrons |
| 92 | (a) I and II only |
| 93 | (c) Protons in its nucleus |
| 94 | (d) Isotopes |
| 95 | (a) The same mass number but different atomic numbers |
| 96 | (b) Niels Bohr |
| 97 | (b) Atomic nucleus |
| 98 | (a) II, III, IV, I |
| 99 | (c) Valency |
| 100 | (d) Atomic number |
Key facts from Basics of Everyday Science
- Inductive reasoning draws a general conclusion from specific observations; a control variable is kept constant in an experiment; communicating the results is the last step of the scientific method.
- Newton’s second law relates force, mass and acceleration; the recoil of a gun illustrates the third law.
- Momentum is the product of mass and velocity; impulse is equal to the change in momentum.
- A satellite in uniform circular orbit is held by the centripetal force provided by gravity.
- Water (H₂O) and N₂ show covalent bonding; sodium chloride, MgO and CaF₂ are ionic.
- The classical cell theory does not say that all cells have a true nucleus.
Frequently asked questions
How many RAS Prelims practice MCQs are there on Basics of Everyday Science?
This page has 200 practice MCQs on Basics of Everyday Science (Science and Technology). Each has the correct answer, and most have an explanation.
What is the product of mass and velocity called?
Momentum. Newton’s second law says that the rate of change of momentum is equal to the force applied, and impulse is equal to the change in momentum of a body.
Which law explains the recoil of a gun?
Newton’s third law of motion. The gun pushes the bullet forward, and the bullet pushes the gun back with an equal and opposite force, which is felt as recoil.
What holds a satellite in a circular orbit?
The centripetal force provided by gravity. The Earth’s pull keeps changing the direction of the satellite’s velocity so that it moves in a circle and does not fly off in a straight line.