This set of Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “p-Block Elements – Group 13 Elements: Boron Family”.
1. Are group 13 elements a part of p block elements?
c) Only a few
d) Only one
Explanation: The last electron enters in the outermost p-orbital in the p block elements, from group 13 to group 18 the entire elements belong to p-block, whereas group 13 is called a boron family. It includes the elements boron, aluminum, gallium, indium and thallium.
2. Which of the following group’s elements have smaller atomic radii?
a) Group 1 elements
b) Group 2 elements
c) Group 13 elements
d) All have the same atomic radii
Explanation: Group 13 elements have smaller atomic radii and ionic radii than those of alkaline earth metals and alkali metals due to the greater effective nuclear charge, atomic radii increases on going down the group with an abnormality at gallium.
3. The atomic radius of gallium is greater than that of aluminum.
Explanation: Though the atomic radii increase on going down the group, the radius of gallium decreases unexpectedly because of the presence of electrons in the orbitals which do not screen the attraction of the nucleus effectively. So the atomic radius of gallium is less than that of aluminium.
4. Gallium remains liquid up to __________ Kelvin.
Explanation: Low melting point of gallium is due to the fact that it consists of Ga2 molecules and gallium remains liquid up to 2276 k. Hence it is used in high-temperature thermometer. Gallium as a chemical symbol that is Ga and its atomic number is given as 31.
5. The ionization enthalpy _________ down the group in the family.
d) Is a regular
Explanation: On moving down the group, ionization enthalpy decreases from Boron to aluminium, but the next element gallium has slightly higher ionization enthalpy than aluminium due to the poor shielding of intervening d-electrons, it again increases in indium and then decreases in the last element thallium.
6. Inert pair affect __________ down the group.
d) Is a regular
Explanation: Inert pair effect is the reluctance of the selections of the valence shell to take part in bonding, it occurs due to pore shielding of ns2 electrons by intervening d-electrons and f-electrons, down the group, it increases. The below elements of the group exhibit lower oxidation States.
7. Which of the following element exhibits + 3 Oxidation State only?
Explanation: Boron and aluminium exhibit oxidation state of + 3 only, while gallium, indium and thallium exhibit oxidation states of both +1 and +3. As we move down the group, the tendency to exhibit + 3 Oxidation State decreases this occurs due to the inert pair effect.
8. Which of the following is true regarding reducing character?
a) Gallium < aluminium > indium > thallium
b) Aluminium > gallium > indium > thallium
c) Aluminium > gallium < indium > thallium
d) Gallium > aluminium > indium > thallium
Explanation: Reducing character of the boron family decreases down the group from aluminium to thallium because of the increase in electrode potential value for M3+/M, therefore, the correct order is given as aluminium > gallium > indium > thallium.
9. Complex formation is more likely to be possible in __________
a) alkali metals
b) alkaline earth metals
c) boron family
d) equally likely
Explanation: The complex formation in the boron family is greater than the S block elements due to their smaller size and greater charge. So they can form complexes more likely than alkali metals and alkaline earth metals.
10. The compounds formed by the Boron family are __________
c) both ionic and covalent
d) neither ionic nor covalent
Explanation: Ionic compound formation’s tendency increases from Boron to thallium. Boron can only form covalent compounds, whereas aluminium can form both covalent as well as ionic compounds. Gallium forms mainly ionic compounds.
11. What is the chemical formula of aluminium carbide?
Explanation: 4 moles of aluminium atom combines with 3 moles of carbon atom on heating, in order to form aluminium carbide. Aluminium carbide is ionic in nature and it also forms methane with water. Its chemical formula is given by AlC3.
12. When boron reacts with nitrogen which of the following compound is formed?
a) Boron oxide
b) Boron nitrate
c) Boron hydrides
d) Boron nitride
Explanation: On heating, two moles of boron atom combine with one mole of a nitrogen molecule in order to form 2 moles of boron nitride. Aluminium also when reacted with nitrogen forms aluminium nitride in the same way.
13. What forms when boron combines with caustic soda?
a) Formation of oxygen
b) Formation of washing soda
c) Formation of Boron nitride
d) Formation of sodium borate
Explanation: Two moles of boron atoms fuse with 6 moles of sodium hydroxide in order to form 2 moles of sodium borate and three moles of hydrogen molecules. Sodium hydroxide is also known as caustic soda.
14. The metallic character of __________ is less than that of alkaline earth metals.
a) Boron family
b) Alkali metals
Explanation: The elements of the Boron family are less electropositive than the alkaline earth metals due to their smaller size and higher ionization enthalpies. On moving down the group, the electropositive character first increases from Boron to aluminium and then decreases from gallium so thallium due to the presence of d and f orbitals which causes poor shielding.
15. Which of the following is the correct order for the stability of plus one oxidation State?
a) Ga < In < Tl
b) Ga < In > Tl
c) Ga > In < Tl
d) Ga > In > Tl
Explanation: The correct order of the increased stability of + 1 oxidation state in gallium, indium and thallium is that; gallium stability is less than that of indium and indium stability is less than that of thallium.
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