Boron family is the first group of the p block. It comprises Boron (B), Aluminum (Al), Gallium (Ga), Indium (In) and Thallium (Tl). It is also known as triels due to three electrons in its outermost shell.
Boron family shows a general configuration of ns2 npx1 and oxidation states of +1 and +3.
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Definition: Boron family is the first group of the p block. It comprises Boron (B), Aluminum (Al), Gallium (Ga), Indium (In) and Thallium (Tl). |
Boron Family Chemistry Questions with Solutions
Q1. What is the atomic number of thallium?
(a) 81
(b) 77
(c ) 66
(d) None of the above
Answer: (a) The atomic number of thallium is 81.
Q2. Which of the following element primarily shows a +1 oxidation state?
(a) Boron
(b) Aluminium
(c ) Thallium
(d) None of the above
Answer: (c ) Thallium primarily shows a +1 oxidation state.
Q3. Which of the following electrolyte is used to extract aluminium?
(a) Pure alumina with bauxite and molten cryolite
(b) Fused cryolite with fluorspar
(c ) Pure alumina in molten cryolite
(d) Fused cryolite with felspar
Answer: (c ) Pure alumina in molten cryolite is used to extract aluminium.
Q4. The electrolytic refining of aluminium is known as
(a) Hoop’s process
(b) Baeyer’s process
(c ) Serpeck’s process
(d) None of the above
Answer: (a) The electrolytic refining of aluminium is known as Hoop’s process.
Q5. Which of the following is the hardest compound of boron?
(a) Boron carbide
(b) Boron fluoride
(c ) Boron nitride
(d) None of the above
Answer: (c ) Boron nitride is the hardest compound of boron.
Q6. How does the oxidation state varies when we move from boron to thallium?
Answer: When we move from boron to thallium, the stability of the +3 oxidation state decreases while that of the +1 oxidation state increases.
Q7. Why is BCl3 more than stable TlCL3?
Answer: BCl3 is more than stable TlCL3 because, in boron (2 s2, 2 px1), all three valence electrons are available for bonding with chlorine. While in TlCl3 (6 s2, 6 px1), the 6s orbital experiences a maximum screening effect. Thus, only 6 p1 electron is available for bonding with chlorine, making BCl3 more than stable TlCL3.
Q8. What happens when we heat boric acid?
Answer: Boric acid (H3BO3) forms metaboric acid (HBO2) when heated above 370K, while on further heating, it oxidises to boric oxide (B2O3)
H3BO3 + Heat → HBO2 + Heat → B2O3
Q9. How can you prove the amphoteric nature of aluminium?
Answer: We can justify the amphoteric nature of aluminium by reacting it with an acid and a base.
Reaction with an Acid: Aluminium reacts with an acid to yield salt and hydrogen gas.
2 Al + 6 HCl → 2 AlCl3 + 3 H2 ↑
Reaction with a base: Aluminium reacts with a base to yield salt and hydrogen gas.
2 Al + 2 NaOH + 6 H2O → 2 Na + [Al(OH)4] – + 3 H2 ↑
Q10. Why is the bond length of the B-F bond longer in BF4– while shorter in BF3?
Answer: The bond length of the B-F bond is longer in BF4– while shorter in BF3 because the BF4– is sp3 hybridised while BF3 is sp2 hybridised. An sp3 hybridised orbital is longer than the sp2 hybridised orbital. Thus, the bond length of the B-F bond is longer in BF4– while shorter in BF3.
Q11. Why do boron halides form addition compounds with ammonia and amines?
Answer: Boron halides are electron deficient in nature, so they form additional compounds with electron-rich species like ammonia and amines.
Q12. Why does gallium have large ionisation enthalpy than aluminium?
Answer: Gallium has larger ionisation enthalpy than aluminium because gallium has a poor screening effect, due to which the effective nuclear charge in gallium increases.
Thus, gallium has higher ionisation enthalpy than aluminium.
Q13. Mention any two similarities and differences between aluminium and boron.
Answer:
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Similarities between Aluminium and Boron |
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|---|---|---|
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S. No. |
Aluminium |
Boron |
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1. |
It has three valence electrons. |
It has three valence electrons. |
|
2. |
Its electronic configuration is [Ar] 3s2 3px1. |
Its electronic configuration is [He] 2s2 2px1. |
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Differences between Aluminium and Boron |
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|---|---|---|
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S. No. |
Aluminium |
Boron |
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1. |
It is metal. |
It is a non-metal. |
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2. |
It forms basic oxide. |
It forms acidic oxide. |
Q14. How does boron differ from other members of group 13?
Answer: Boron is different from other members of group 13.
1. Boron is a metalloid, while the other members of group 13 are post-transition metals.
2. Boron oxides and hydroxides are acidic in nature, while the other members of group 13 form amphoteric oxides.
3. Boron forms covalent compounds, while the other members of group 13 form ionic and covalent bonds.
4. Boron has a high melting point and boiling point, while the other members of group 13 have relatively lesser melting and boiling points.
5. Boron is hard, while the other members of group 13 are comparatively softer.
Q15. Why does boron show anomalous behaviour?
Answer: Boron shows a few anomalous properties from other members of the group. It is because of
1. Small size.
2. High Ionisation energy
3. High charge/size ratio.
Practise Questions on Boron Family
Q1. What is the order of acidity of boron halides?
(a) BI3 > BF3 > BBr3 > BCl3
(b) BF3 > BCl3 > BBr3 > BI3
(c ) BI3 > BBr3 > BCl3 > BF3
(d) BBr3 > BCl3 > BI3 > BF3
Q2. Why does gallium have less atomic radius than aluminium?
Q3. Why [BF6]3− doesn’t exist?
Q4. Why can’t we store nitric acid in an aluminium container?
Q5. Why doesn’t B3+ ion exist?
Click the PDF to check the answers for Practice Questions.
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