How many electron pairs are shared between the two atoms in a nitrogen molecule?
- A.One
- B.Two
- C.Three
- D.Four
Correct answer
Explanation
The correct answer is C, three. A nitrogen atom has five valence electrons and needs three more to complete its octet, so two nitrogen atoms share three pairs of electrons and form a triple bond, written N to N with three lines. That triple bond, made of one sigma and two pi bonds, is very strong, which is why nitrogen gas is so unreactive that it is used to fill food packets and to provide an inert atmosphere. Option A is wrong because one shared pair would make a single bond, as in the hydrogen or chlorine molecule. Option B is wrong because two shared pairs make a double bond, as in the oxygen molecule or in ethylene. Option D is wrong because no ordinary covalent molecule of nitrogen shares four pairs; the octet rule allows at most three here. Remember the set: hydrogen single, oxygen double, nitrogen triple.
Read the full article: Chemical Bonding and Reactions: Types, Rules and Facts
Practice Questions
View allWhich of the following is NOT a double displacement reaction?
- A.BaCl2 + H2SO4 → BaSO4 + 2HCl
- B.2H2 + O2 → 2H2O
- C.CuSO4 + H2S → CuS + H2SO4
- D.NaOH + HCl → NaCl + H2O
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In a double displacement reaction two compounds exchange their ions, so both reactants must be compounds. Here hydrogen and oxygen are elements combining to form a single product, water, which makes it a combination reaction and also a combustion and redox reaction, but certainly not a double displacement.
Read the full explanation →Which among the following compounds has a double bond?
- A.Ethane
- B.Methane
- C.Acetylene
- D.Ethylene
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Ethylene, also called ethene, has the formula C2H4, and its two carbon atoms share two pairs of electrons, which is a carbon-carbon double bond made of one sigma and one pi bond; it is the simplest alkene.
Read the full explanation →The number of sigma and pi bonds in benzene, respectively, is:
- A.12 and 3
- B.3 and 3
- C.6 and 3
- D.9 and 3
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Benzene has the formula C6H6 and a ring of six carbon atoms, each carrying one hydrogen. Count the sigma bonds first: six carbon-carbon bonds around the ring and six carbon-hydrogen bonds give twelve sigma bonds.
Read the full explanation →Which of the following is an amphoteric oxide?
- A.Aluminium oxide
- B.Iron (II) oxide
- C.Magnesium oxide
- D.Carbon dioxide
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An amphoteric oxide reacts with both acids and bases to give a salt and water. Aluminium oxide dissolves in hydrochloric acid to give aluminium chloride and in sodium hydroxide to give sodium aluminate, so it behaves as a base in one case and as an acid in the other.
Read the full explanation →Which of the following is used as a catalyst in the hydrogenation of vegetable oil?
- A.Pb
- B.Ni
- C.H2
- D.He
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Vegetable oils contain unsaturated fatty acids with carbon-carbon double bonds, and when hydrogen is passed through the oil at about 60 degrees Celsius in the presence of finely divided nickel, the double bonds add hydrogen and become saturated, turning the liquid oil into semi-solid vanaspati.
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