This set of Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “P-Block – Group 16 Elements”.
1. Group 16 elements are also called Chalcogens.
Explanation: Group 16 elements, also known as the Oxygen family, are also called Chalcogens (pronounced as kal’-ke-jens) (meaning ore forming elements) because many metals occur as oxides and sulphides.
2. Which of the following elements does not belong to group 16 of the periodic table?
Explanation: Group 16 of the periodic table consists of five elements viz., Oxygen (O), Sulphur (S), Selenium (Se), Tellurium (Te) and Polonium (Po). The elements of this group are commonly known as the oxygen family after the name of its first member.
3. Which is the most abundant group 16 element?
Explanation: Oxygen is the most abundant of all elements. It occurs in the free state as dioxygen (O2) and makes up 20.46% by volume and 23% by mass of the atmosphere. It also occurs in the form of ozone (O3).
4. Ozone is an allotrope of Oxygen.
Explanation: Oxygen also occurs as ozone (O3), an allotrope of oxygen, in the upper atmosphere which protects us from the harmful radiations of the sun. Ozone is a pale blue gas with a distinctively pungent smell.
5. What is the general outer electronic configuration of the Oxygen family?
Explanation: The elements of group 16 have six electrons in the valence shell and hence their general outer electronic configuration is ns2np4. The four p-electrons are arranged in three p-orbitals as px2py1pz1 in accordance with Hund’s rule.
6. Which of the following statements regarding group 16 elements is not true?
a) The electronic configuration of Oxygen is [He]2s22p4
b) The electronic configuration of Sulphur is [Ne]3s23p4
c) The atomic radii of the elements of group 16 are larger than those of the corresponding elements of group 15
d) The electronic configuration of Tellurium is [Kr]4d105s25p4
Explanation: When you move across the periodic table, from left to right, the atomic size of the respective elements decreases due to increase in nuclear charge. Therefore, the atomic radii of the elements of group 16 are smaller than those of the corresponding elements of group 15.
7. Which group 16 element is the most electronegative?
Explanation: The elements of group 16 have higher values of electronegativity than the corresponding elements of group 15. Actually, oxygen is the second most electronegative element (EN=3.5), the first being fluorine (EN=4.0).
8. Which of the following is radioactive in nature?
Explanation: Oxygen is the most non-metallic element of group 16. Sulphur is also a typical non-metal and Tellurium is a metalloid. Polonium is, however, metallic in nature but is radioactive with a short half-life (13.8 days).
9. Which of the following does not exist as an octatomic solid?
Explanation: Oxygen exists as a diatomic gas at room temperature while other elements (S, Se and Te) exist as octatomic solids. Due to small size and high electronegativity, oxygen atom forms pπ – pπ double bond with other oxygen atom to form O = O molecule. The intermolecular forces of attraction between oxygen molecules are weak van der Waals forces and hence oxygen exists as a diatomic gas at room temperature.
10. Which group 16 element has the highest tendency for catenation?
Explanation: Sulphur has a stronger tendency for catenation than Oxygen. Due to small size, the lone pairs on the Oxygen atoms repel the bond pair of the O-O bond to a greater extent than the lone pairs of electrons on the Sulphur atoms in S-S bond. As a result, S-S bond is much stronger than O-O bond and hence Sulphur has a much stronger tendency for catenation than Oxygen.
11. Which group 16 element has 8 allotropic forms?
Explanation: Selenium has eight allotropic forms, of which three are red monoclinic forms containing Se8 rings. The thermodynamically most stable form is grey hexagonal metallic Selenium which consists of polymeric helical chains.
12. What is the most reactive element of group 16?
Explanation: Oxygen is the most reactive element of group 16. It is the second most electronegative element in the periodic table (EN=3.5), the first being fluorine (EN=4.0), making it more reactive than the other elements of the group.
13. Which of the following is a photosensitive element?
Explanation: The grey form of Selenium (metallic) and Tellurium consist of parallel chains held by weak metallic bonds. In the presence of light, the weak metallic bonds are excited and as a result, the number of free electrons increases and so does the conductivity. Thus, these elements conduct electricity significantly only in the presence of light. That is why Se and Te are called photosensitive elements.
14. What is the correct order of reactivity of group 16 elements?
a) O > Se > S > Te > Po
b) S > O > Te > Po > Se
c) S > O > Se > Te > Po
d) O > S > Se > Te > Po
Explanation: Oxygen is the most reactive group 16 element. Its reactivity is only slightly less than the most reactive elements, halogens. Sulphur is also very reactive particularly at high temperatures which helps in the cleavage of S-S bonds present in S8 molecules. However, as we move down the group, the reactivity decreases, i.e., O > S > Se > Te > Po.
15. Which of the following is not poisonous?
Explanation: The hydride of Oxygen, i.e., H2O is a colourless, odourless liquid while the hydrides of all the other group 16 elements are unpleasant, foul smelling, poisonous gases. H2O has the highest boiling point of 373 K amongst the hydrides of group 16 elements.
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