Valency refers to the combining capacity of an element, i.e. number of monovalent hydrogen atoms that can directly attach to it. For any element with four or fewer valence electrons, valency is equivalent to the number of valence electrons. For atoms with more than four valence electrons, valency equals 8 – the number of valence electrons.
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Definition: Valency equals the number of valence electrons for atoms having four or fewer valence electrons. For atoms with more than four valence electrons, valency equals 8 – the number of valence electrons. Carbon has four valence electrons in its valence shell. Thus, it has four valency. |
Valency of Carbon Chemistry Questions with Solutions
Q1. What is the valency of carbon?
(a) Three
(b) Four
(c) Both (a) and (b)
(d) None of the above
Answer: (b) Four
Explanation: Carbon has four valence electrons in its outermost shell. Thus, its valency is four.
Q2. What is the valency of carbon in carbon dioxide (CO2)?
(a) Two
(b) Four
(c) Both (a) and (b)
(d) None of the above
Answer: (b) Four
Calculation: Let x be the valency of the carbon atom.
Valency of oxygen = – 2.
Thus, the valency of carbon will be
x + 2 X (-2) = 0
x – 4 = 0
x = 4
Thus, the valency of carbon in carbon dioxide (CO2) is four.
Q3. What is the atomic number of carbon?
(a) Four
(b) Five
(c) Six
(d) None of the above
Answer: (c) Six
Q4. Why does carbon forms multiple compounds?
(a) Tetravalency
(b) Catenation
(c) Shares multiple electrons to form a double or triple bond
(d) All of the above
Answer: (d) All of the above
Q5. How many double bonds can a carbon atom form?
(a) One
(b) Two
(c) Both (a) and (b)
(d) None of the above
Answer: (b) Two
Explanation: Carbon has four valency. Thus, it can form at most two double bonds.
Q6. Why does carbon show four valency?
Answer: Valency is equivalent to the number of valence electrons for atoms having four or fewer valence electrons. For atoms with more than four valence electrons, valency equals 8 – the number of valence electrons. Carbon has four valence electrons in its outer shell. Thus, it shows four valency.
Q7. What is valency?
Answer: Valency is the combining capacity of an element, i.e. number of monovalent hydrogen atoms that can directly attach to it.
Q8. What is the meaning of four valency?
Answer: Four valency signifies that the element is tetravalent, i.e. it can combine with four univalent atoms. Carbon, silicon, germanium, tin and lead show four valency.
Q9. What is the valency of the first ten elements?
Answer:
|
S. No. |
Element |
Valency |
|---|---|---|
|
1. |
Hydrogen |
1 |
|
2. |
Helium |
0 |
|
3. |
Lithium |
1 |
|
4. |
Berelium |
2 |
|
5. |
Boron |
3 |
|
6. |
Carbon |
4 |
|
7. |
Nitrogen |
3 |
|
8. |
Oxygen |
2 |
|
9. |
Fluorine |
1 |
|
10. |
Neon |
0 |
Q10. Is valency positive or negative?
Answer: Valency is neither positive nor negative but neutral.
Q11. What are allotropes? Name any three allotropes of carbon.
Answer: Allotropes refer to the different forms of the same element, where the atoms combine in different ways, so at the same temperature and pressure, they can exist in different forms.
Graphite, diamond and fullerene are the allotropes of carbon.
Q12. Does LPG contain carbon?
Answer: Yes, LPG contains carbon. It is a mixture of butane and isobutane (carbon compounds).
Q13. Why does carbon not form a C4+ cation?
Answer: Carbon does not form a C4+ cation because donating four electrons from a carbon atom requires significant energy, which is unavailable. Thus, it does not form a C4+ cation.
Q14. What are the three primary uses of carbon?
Answer: The three primary uses of carbon are as follows:
1. Carbon is used as a fuel (in the form of coal), which is predominantly carbon.
2. Graphite is used to make pencil tips, high-temperature crucibles, dry cells, electrodes, and lubricants, which is an allotrope of carbon.
3. Diamonds are used in jewellery and industry for cutting, drilling, grinding, and polishing due to their extreme hardness, which is also an allotrope of carbon.
Q15. Why does carbon not form a C4- anion?
Answer: Carbon does not form a C4- anion because carbon is tiny and contains six protons. It is ineligible to hold ten valence electrons. Thus, it does not form a C4- anion.
Practice Questions on Valency of Carbon
Q1. Why does carbon forms multiple compounds?
Q2. How do you calculate the valency of an atom?
Q3. Why does carbon not form ionic bonds?
Q4. What is covalency? What is the covalency of carbon?
Q5. Why is carbon tetravalent?
Click the PDF to check the answers for Practice Questions.
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