Structure Of Atoms: Important Questions

Very Short Answer Questions [1 Mark Questions]

Ques. Who invented atomic structure? 

Ans. Atomic Structure was first given by John Dalton in the year 1808.

Atomic Theory by John Dalton

Ques. Give the charge which electron (e) upholds.

Ans. The universal charge that electron (e) upholds via Millikan's experiment is –1.6 * 10^-19 C.

Ques. Give the charge value of the proton. 

Ans. The charge which proton holds is + 1.602 * 10^-19 C. 

Ques. What is the charge of a neutron?

Ans. The charge of a neutron is zero (0) as it is electrically neutral. 

Electron, Proton, and Neutron

Ques. What is the mass of an electron?

Ans. The mass of an electron is 9.10 * 10^-31 Kg.

Ques. What is the mass of a proton?

Ans. The mass of a proton is 1.676 * 10^-27 Kg.

Ques. What is the mass of a neutron?

Ans. The mass of a neutron is 1.676 * 10^-24 g.

Ques. Define an atom.

Ans. The smallest unit of an element is known as an atom. An atom is made up of three structures namely; electron, proton, and neutron.

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Short Answer Questions [2 Marks Questions] 

Ques. What do you mean by isotopes? Also, give an example of it.

Ans. Isotopes are the atoms of the same element which hold the same atomic number but a different mass number. Isotopes hold almost the same chemical properties.

For example - \(^{1}_{1}H\), \(^{2}_{1}H\) and \(^{3}_{1}H\), \(^{35}_{17}Cl\) and \(^{37}_{17}Cl\), \(^{12}_{6}C\), \(^{13}_{6}C\) and \(^{14}_{6}C\).

Isotopes of Hydrogen Atom

Ques. What is the meaning of an isobar? Give some examples of isobar.

Ans. Isobars are atoms of different elements which have the same mass number but an atomic number. Isobars have almost the same physical properties and different chemical properties.

For example - \(^{14}_{6}C\), \(^{14}_{7}N\) , \(^{40}_{18}Ar\), \(^{40}_{19}K\), \(^{40}_{20}Ca\).

Ques. What do you mean by isotones? Give some examples.

Ans. – Isotopes are atoms that are of different elements but have a different set of neutrons.

For example - \(^{14}_{6}C\), \(^{15}_{7}N\), \(^{16}_{8}O\).

Ques. What was the first atomic model?

Ans. – The Raisin pudding model is the first atomic model. It was given by J.J. Thomson in the year 1989. In this model, negative charges are considered by raisins which get spread around the plum.

Ques. Elucidate the meaning of mass number and atomic number.

Ans. The mass number denotes the total number of protons and neutrons which are present in the nucleus of an atom. Whereas atomic number is the total measure of protons present in the atom of an element.

Ques. What conclusion does Rutherford exemplify?

Ans. Rutherford's Model gives the conclusion that the atom holds great space with electrons that orbit around a fixed positively charged nucleus.

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Long Answer Questions [3 Marks Questions]

Ques. What does the photoelectric effect mean?

Ans. The photoelectric effect was given by H. Hertz in the year 1887. The photoelectric effect is a phenomenon in which metals emit electrons when they are confronted with a high-frequency beam of light. Through this phenomenon, electrons get emitted which are known as photoelectrons.

Ques. What is Heisenberg’s Uncertainty Principle?

Ans. Heisenberg's uncertainty principle is based on wave-particle duality. In the study of quantum mechanics, Heisenberg's Uncertainty Principle comes into play. It is a theory that elucidates that it is not possible to measure the position and momentum of an object.

The formula of Heisenberg's Uncertainty Principle is – 

\(\Delta x \Delta p \ge \frac{h}{4\pi}\). 

Where, 

Delta X implies an error in position measurement 

Delta Y implies an error in the measurement of momentum 

Ques. What is de – Broglie's relation equation?

Ans. De-Broglie's equation elucidates that a matter can behave as a wave in the same way light and radiation behave like waves. By this equation, it becomes clear that electrons possess dual nature characteristics.

The de – Broglie’s equation is – 

\(\lambda =\frac{h}{p}=\frac{h}{mv}\)

Where,

Lamda implies the wavelength of a particle 

h implies the Planck's Constant

p implies the momentum of a particle

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Very Long Answer Questions [5 Marks Question]

Ques. In Sulfur (Z = 16) how many electrons are there if, n + l = 3?

Ans. In Sulfur (Z = 16), the electronic configuration will be, 

₁₆S = 1s², 2s² 2p⁶ 3s² 3p⁴

In this,

For 1s², n + l = 1 + 0 = 1

For 1s², n + l = 2 + 0 = 2

For 2p⁶, n + l = 2 + 1 = 3

For 3s², n + l = 3 + 0 = 3

For 3p⁴, n + l = 3 + 1 = 4

Therefore,

n + l = 3 for 2p⁶ and 3s² electrons, which implies there are a total 8 electrons.

Ques. What is the canal ray experiment?

Ans. Canal ray experiment was deduced in the year, 1886 by Eugen Goldstein who was a German scientist. In the experiment, high voltage was applied across the discharge tube which upholds a perforated cathode.

In this experiment, when high voltage is passed the gas gets ionized and the positive ions of the gas make up the canal ray. The kernel of the gas comes into use and it shows the properties different from cathode rays.

Via this experiment, it can be concluded,

1. Canal rays depend on the natural gas which is present in the tube, as the canal rays are composed of positive ionized ions which are formed by the ionization of the gas.
2. The behavior of particles in a magnetic field and the electric field is opposite when compared to cathode rays.

Canal Ray Experiment

Ques. What is Bohr's theory of the atom?

Ans. Bohr’s theory of an atom was proposed by Neil Bohr in 1915. It was a step that came forward in response to modifications of Rutherford’s model of an atom. Bohr's theory is applicable when concerned with a modified atomic structure which elucidates that electrons move in specific orbits which are also known as shells and not in any other way around.

Bohr’s Atomic Model

Bohr via his model stretched Rutherford's nucleus statement by adding electrons and their energy levels in the scene. In the model a small positively charged nucleus gets surrounded by negative electrons which move around the nucleus.

Through this experiment, Bohr concluded that an electron that is located far from the nucleus upholds greater energy than the electrons which are closer to the nucleus.

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