Atomic Structure

41. What is the maximum number of electrons that can be accommodated in th

What is the maximum number of electrons that can be accommodated in the M shell of an atom?

[amp_mcq option1=”32″ option2=”18″ option3=”8″ option4=”2″ correct=”option2″]

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The correct answer is 18.
The maximum number of electrons that can be accommodated in an electron shell is given by the formula 2n², where ‘n’ is the principal quantum number of the shell.
Electron shells are denoted by K, L, M, N, … corresponding to principal quantum numbers n = 1, 2, 3, 4, … respectively. For the M shell, n=3. Therefore, the maximum number of electrons in the M shell is 2 * (3)² = 2 * 9 = 18.

42. How many valence electrons are present in Cl – ion?

How many valence electrons are present in Cl– ion?

[amp_mcq option1=”0″ option2=”8″ option3=”7″ option4=”1″ correct=”option2″]

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Chlorine (Cl) has an atomic number of 17. Its electronic configuration is 1s² 2s² 2p⁶ 3s² 3p⁵. The outermost shell (n=3) is the valence shell, which contains 2 + 5 = 7 valence electrons. The Cl⁻ ion is formed when a neutral chlorine atom gains one electron to achieve a stable octet configuration. The electronic configuration of Cl⁻ becomes 1s² 2s² 2p⁶ 3s² 3p⁶. The valence shell (n=3) now contains 2 + 6 = 8 electrons.
A neutral chlorine atom has 7 valence electrons. A chloride ion (Cl⁻) gains one electron to complete its valence shell, resulting in 8 valence electrons.
Ions tend to form by gaining or losing electrons to achieve a stable electron configuration, often a full valence shell (octet rule for many elements). Cl⁻ achieves a stable octet configuration in its valence shell.

43. Name the scientist who was NOT associated with the work of periodic cl

Name the scientist who was NOT associated with the work of periodic classification of elements?

[amp_mcq option1=”Dmitri Mendeleev” option2=”Robert Bunsen” option3=”Johann Wolfgang Dobereiner” option4=”John Newlands” correct=”option2″]

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Robert Bunsen was NOT primarily associated with the work of periodic classification of elements.
Dmitri Mendeleev is credited with developing the modern periodic table. Johann Wolfgang Dobereiner proposed the Law of Triads, an early attempt at classification. John Newlands proposed the Law of Octaves, another early attempt. Robert Bunsen was a chemist famous for inventing the Bunsen burner and his work in spectroscopy, which led to the discovery of elements like Cesium and Rubidium, but his main contribution was not to the theory or system of periodic classification itself.
While Bunsen’s work in spectroscopy was crucial for identifying new elements that fit into the periodic table, his focus was on analytical chemistry and identification rather than the systematic arrangement of elements based on their properties.

44. Which one among the following is responsible for determining the chemi

Which one among the following is responsible for determining the chemical properties of an element ?

[amp_mcq option1=”Protons” option2=”Electrons” option3=”Neutrons” option4=”Nucleus” correct=”option2″]

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Electrons are responsible for determining the chemical properties of an element.
An element’s chemical properties dictate how it reacts and forms bonds with other elements. This behavior is governed by the configuration of its electrons, particularly the valence electrons in the outermost shell, which are involved in chemical interactions.
Protons, located in the nucleus, determine the atomic number and thus the identity of the element. Neutrons, also in the nucleus, affect the atomic mass and form isotopes but have little direct impact on chemical reactivity. The nucleus (containing protons and neutrons) determines the atom’s mass and stability, but the electron cloud outside the nucleus dictates its chemical behavior.

45. The two isotopes of elemental chlorine are :

The two isotopes of elemental chlorine are :

[amp_mcq option1=”$^{35}_{17}$C and $^{36}_{17}$C” option2=”$^{34}_{17}$C and $^{36}_{18}$C” option3=”$^{35}_{17}$C and $^{37}_{18}$C” option4=”$^{35}_{17}$C and $^{37}_{17}$C” correct=”option4″]

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Isotopes of an element are atoms that have the same number of protons (atomic number) but different numbers of neutrons (leading to different mass numbers). The atomic number is represented by the subscript, and the mass number by the superscript before the element symbol. Chlorine (Cl) has an atomic number of 17. Assuming the element symbol ‘C’ in the options is a typo for ‘Cl’, option D, $^{35}_{17}$C and $^{37}_{17}$C, correctly shows the same atomic number (17) but different mass numbers (35 and 37), fitting the definition of isotopes of Chlorine-17.
– Atomic number (number of protons) defines the element.
– Mass number is the sum of protons and neutrons.
– Isotopes of the same element have the same atomic number but different mass numbers.
Naturally occurring chlorine is a mixture of two main isotopes: $^{35}_{17}$Cl (approximately 75.77% abundance) and $^{37}_{17}$Cl (approximately 24.23% abundance). The average atomic mass of chlorine is approximately 35.45 u.

46. Which one among the following are the correct symbols for the elements

Which one among the following are the correct symbols for the elements gold, tin and lead, respectively ?

[amp_mcq option1=”Ga, Sb, Pb” option2=”At, Sn, Le” option3=”Au, Sn, Pb” option4=”Au, Sb, Pb” correct=”option3″]

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The question asks for the correct chemical symbols for the elements gold, tin, and lead, respectively. The internationally recognized symbols are Au for gold, Sn for tin (from its Latin name Stannum), and Pb for lead (from its Latin name Plumbum).
Chemical symbols are standard abbreviations used to represent elements. Many symbols are derived from the element’s English name (e.g., O for Oxygen, H for Hydrogen), but some are derived from their historical Latin or Greek names to maintain uniqueness and historical consistency.
Option A lists Ga (Gallium), Sb (Antimony), Pb (Lead). Option B lists At (Astatine), Sn (Tin), Le (not a standard symbol). Option D lists Au (Gold), Sb (Antimony), Pb (Lead). Only option C provides the correct symbols for all three elements: Au, Sn, and Pb.

47. Cl$^{-}$ is not isoelectronic with

Cl$^{-}$ is not isoelectronic with

[amp_mcq option1=”K$^{+}$” option2=”Mg$^{2+}$” option3=”S$^{2-}$” option4=”P$^{3-}$” correct=”option2″]

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Isoelectronic species are atoms or ions that have the same number of electrons. Cl$^{-}$ has an atomic number of 17, so Cl has 17 electrons. Cl$^{-}$ has gained one electron, giving it 17 + 1 = 18 electrons. We need to find the species among the options that does not have 18 electrons.
– K$^{+}$: Atomic number of K is 19. K$^{+}$ has lost one electron, so it has 19 – 1 = 18 electrons.
– Mg$^{2+}$: Atomic number of Mg is 12. Mg$^{2+}$ has lost two electrons, so it has 12 – 2 = 10 electrons.
– S$^{2-}$: Atomic number of S is 16. S$^{2-}$ has gained two electrons, so it has 16 + 2 = 18 electrons.
– P$^{3-}$: Atomic number of P is 15. P$^{3-}$ has gained three electrons, so it has 15 + 3 = 18 electrons.
Thus, Cl$^{-}$ (18 electrons) is not isoelectronic with Mg$^{2+}$ (10 electrons).
Other common isoelectronic series with 18 electrons include Ar, Ca$^{2+}$, Sc$^{3+}$. The electronic configuration for all species with 18 electrons is 1s²2s²2p⁶3s²3p⁶, which is the electron configuration of the noble gas Argon.

48. Symbol of element was introduced by

Symbol of element was introduced by

[amp_mcq option1=”John Dalton” option2=”Antoine Lavoisier” option3=”Jöns Jacob Berzelius” option4=”Robert Boyle” correct=”option3″]

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Jöns Jacob Berzelius, a Swedish chemist, is credited with introducing the modern system of chemical symbols for elements around 1813. He proposed using one or two letters from the Latin name of the element, with the first letter capitalized and the second lowercase (if present). This system is the basis of the symbols used today in the periodic table.
The modern notation of using one or two letters derived from the element’s name as its symbol was proposed by Berzelius.
John Dalton used unique pictorial symbols for elements in his atomic theory. Antoine Lavoisier contributed significantly to the understanding of elements and chemical nomenclature but did not introduce the system of letter symbols. Robert Boyle is known for his definition of an element in “The Sceptical Chymist” and Boyle’s Law related to gases, but not for introducing element symbols.

49. Consider the following statement: “Atomic number of an element is a mo

Consider the following statement: “Atomic number of an element is a more fundamental property than its atomic mass.” Who among the following scientists has made the above statement?

[amp_mcq option1=”Dmitri Mendeleev” option2=”Henry Moseley” option3=”J.J. Thomson” option4=”Ernest Rutherford” correct=”option2″]

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The statement “Atomic number of an element is a more fundamental property than its atomic mass” is a cornerstone of the modern periodic law. This concept was established by Henry Moseley through his experiments on X-ray spectra of elements.
Dmitri Mendeleev developed the periodic table based on atomic mass, but he noted that some elements needed to be placed out of order by mass to fit their chemical properties into the correct groups. Henry Moseley’s work provided the physical basis for this ordering, showing that the frequency of characteristic X-rays emitted by an element is related to its atomic number (the number of protons in the nucleus), which is a more fundamental property determining chemical behaviour than atomic mass.
J.J. Thomson is known for discovering the electron, and Ernest Rutherford is famous for the gold foil experiment which led to the discovery of the atomic nucleus. While both made crucial contributions to atomic structure, it was Moseley who linked atomic number to the properties that govern the periodic table arrangement.

50. Which one of the following statements is not correct ?

Which one of the following statements is not correct ?

[amp_mcq option1=”Elements are defined by the number of protons they possess.” option2=”Isobars are atoms having the same atomic number but different mass number.” option3=”The mass number of an atom is equal to the number of nucleons in its nucleus.” option4=”Valency is the combining capacity of an atom.” correct=”option2″]

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The statement “Isobars are atoms having the same atomic number but different mass number” is incorrect.
– Elements are defined by their atomic number (number of protons).
– Isobars are atoms of different elements that have the same mass number but different atomic numbers.
– Isotopes are atoms of the same element that have the same atomic number but different mass numbers.
– The mass number is the total number of protons and neutrons (nucleons) in an atom’s nucleus.
– Valency refers to the combining capacity of an atom, determining how it forms chemical bonds.
The number of neutrons in isobars varies, while the sum of protons and neutrons (mass number) remains constant. For example, Carbon-14 and Nitrogen-14 are isobars. Carbon has 6 protons, Nitrogen has 7 protons. Both have a mass number of 14 (6 protons + 8 neutrons for Carbon-14; 7 protons + 7 neutrons for Nitrogen-14).
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