Most Repeated MDCAT Chemistry: Atomic Structure MCQs

Explanation

As the principal quantum number (n) increases, the size of the s-orbitals also increases. The shape of the s-orbitals remains spherical, with a probability distribution that becomes more spread out from the nucleus as n increases. So, while the shape (spherical) remains the same, the size of the orbital increases with higher values of n ( as shown in figure). This means that s-orbitals with larger principal quantum numbers have a higher probability of finding electrons farther away from the nucleus. Therefore, option B is correct.

Explanation

The maximum number of electrons in a single orbital is two. The maximum number of electrons an orbital can accommodate is 2. As in an orbital two electrons can never have the same values of all 4 quantum no.s according to Pauli’s exclusion principle. So to follow this rule, an orbital can accommodate 2 electrons only.

Explanation

Thomson was able to deflect the cathode ray towards a positively charged plate deduce that the particles in the beam were negatively charged. Then Thomson measured how much various strengths of magnetic fields bent the particles. Using this information Thomson determined the mass to charge ratio of an electron.All other options are incorrect because those were not discovered by J.J thomson.

Explanation

The radius of any orbit can be calculated by using formula n^2 (0.53) For 1st orbit; (1)^2(0.53) = 0.53Å For 2nd orbit; (2)^2(0.53) = 2.12Å For 3rd orbit; (3)^2(0.53) = 4.77 Å So, 4.77 Å is radius for third orbit. Hence, option C is correct.

Explanation

Orientation of orbitals are given by magnetic quantum number. By using formula; (2l + 1) we can calculate the orientations of orbitals in space. For s orbital, l=0, so; [2(0) +1] = 1, s orbital will have 1 orientation in space. For p orbital, l=1, so; [2(1) +1] = 3, p orbital will have 3 orientations in space. For d orbital, l=2, so; [2(2) +1] = 5, d orbital will have 5 orientations in space. For f orbital, l=3, so; [2(3) +1] = 7, d orbital will have 7 orientations in space.Hence, option B, s orbital is correct.

Explanation

The mass of proton is 1836 times that of electron. STB Pg- 79 Hence, option A is correct.

Explanation

Lyman series—Correct answer: This series corresponds to transitions where electrons fall to the first energy level (n=1) and lies in the far ultraviolet region of the electromagnetic spectrum.

Explanation

This is the correct answer. Let's break down the quantum numbers:n = 2: This indicates that the electrons are in the second principal energy level. l = 1: This indicates that the electrons are in a p subshell.s = -1/2: This indicates that the electrons have a spin of -1/2. NNow, let's analyze each configuration:1s2: This configuration has 2 electrons in the 1s orbital. Since the 1s orbital has l = 0, none of these electrons can have l = 1. 2s2: This configuration has 2 electrons in the 2s orbital. Since the 2s orbital has l = 0, none of these electrons can have l = 1. 2p3: This configuration has 3 electrons in the 2p subshell.

Explanation

The quantum numbers +1/2 and -1/2 represent the direction of the electron's spin. Electrons can spin in either a clockwise or counterclockwise direction. The +1/2 and -1/2 values indicate these two possible spin orientations.

Explanation

A nucleon is either a proton or a neutron, which are the subatomic particles found in the nucleus of an atom. They are held together by the strong nuclear force, which overcomes the repulsive forces between the positively charged protons. This binding is crucial for the stability and mass of the atom. The other options are incorrect: 'Any atomic nucleus' describes a region, not the specific particles; 'A radioactive atomic nucleus' refers to the behavior of the nucleus, not the definition of nucleons; and 'A neutron proton or an electron' includes an electron, which is not part of the nucleus.

Explanation

When electrons have opposite spins, their magnetic fields align in opposite directions. This results in less repulsion between the electrons because their opposite spins create opposite magnetic fields, leading to a cancellation of magnetic interactions. As a result, option D is correct.