Correct Answer:
(A)
J.J. Thomson
: The "plum pudding model" of the atom was proposed by J.J. Thomson after he discovered the electron. The model envisioned the atom as a sphere of positively charged "pudding" with negatively charged electrons embedded within it, similar to how plums are scattered in a pudding.
Ques:
32
Which particle is free of charge?
Correct Answer:
(C)
Neutron
Among the given particles neutron is free of charge. α (alpha) particle (+2ve) and proton (+ve) are positive charged particles while electron (–ve) carries negative charge.
Ques:
33
Which of the following particles has zero charge?
Correct Answer:
(B)
Neutrino
A neutrino is a subatomic particle that is very similar to an electron, but has no electrical charge and a very small mass, which might even be zero. Neutrinos are one of the most abundant particles in the universe. Because they have very little interaction with matter, however, they are incredibly difficult to detect.
Ques:
34
The alpha particle carries two positive charges. Its mass is very nearly equal to that of –
Correct Answer:
(B)
Nucleus of an atom of helium
An alpha particle is a fast moving particle containing two protons and two neutrons (a helium nucleus). Its mass is equal to that of helium atom's nucleus. Alpha particles carry a charge of +2 and strongly interact with matter. Produced during alpha decay, alpha particles can travel only a few inches through the air and can be easily stopped with a sheet of paper.
Ques:
35
Which of the following elements does not contain neutrons?
Correct Answer:
(C)
Hydrogen
The atomic no. of Hydrogen is 1. The Protium (1H1) isotope of the Hydrogen has no neutron while Deuterium (1H2) has one neutron and Tritium (1H3) isotope has 2 neutrons.
Ques:
36
Which of the following carries a negative charge?
Correct Answer:
(C)
Beta particles
Alpha rays or Alpha particles (α) are the positively charged particles. Beta particles (β) are highly energetic electrons which are released from inner part of a nucleus. They are negatively charged (-1e) and have a negligible mass. Gamma radiation (γ) consist of photons, which travel at the speed of light like all electromagnetic radiations. A ray has no mass or charge. Gamma radiation can travel much faster (speed of light) in the air than alpha and beta.
Ques:
37
In an atom, the order of filling up of the orbitals is governed by –
Correct Answer:
(A)
Aufbau's principle
The Aufbau principle is used to determine the electron configuration of an atom, molecule or ion. The principle postulates a hypothetical process in which an atom is 'built up' by progressively adding electrons. As they are added, they assume their most stable condition (electron orbitals) with respect to the nucleus and those electrons already there. According to the principle, electrons fill orbitals starting at the lowest available (possible) energy levels before filling higher levels (e.g. 1s before 2s).
Ques:
38
The number of electrons and neutrons in an element is 18 and 20 respectively. Its mass number is
Correct Answer:
(C)
38
Given that,
number of neutrons = 20 & number of electrons = 18
Thus, number of protons = number of electrons = 18
Mass number = number of protons + number of neutrons = 18 + 20 = 38
Ques:
39
What is the mass number of an element, the atom of which contains two protons, two neutrons and two electrons?
Correct Answer:
(B)
4
The mass number of an element is the sum of a total number of protons and neutrons inside in its nucleus and represents by A. Therefore, mass number A= number of protons + number of neutrons. Therefore, mass number = 2 + 2 = 4
Ques:
40
The atoms, in which the number of protons is same but the number of neutrons is different, are known as –
Correct Answer:
(D)
Isotopes
The Isotopes are a set of nuclides/atoms having the same number of protons, but a different number of neutrons. In other words, the same atomic number but having different atomic mass. Each individual isotope has a separate nuclei. The Isotopes that are unstable and undergo radioactive decay are called radioisotopes.