Question
A covalent molecule Q contains only six shared electrons.
What is Q?
A ammonia, \(NH_3\)
B chlorine, \(Cl_2\)
C methane, \(CH_4\)
D water, \(H_2O\)
▶️Answer/Explanation
Ans: A
It has 6 shared electrons and 2 electrons as a lone pair.
Question
In which molecule are all the outer shell electrons from each atom used to form covalent bonds?
A \(CH_4\) B \(Cl_2\) C \(H_2O\) D \(NH_3\)
▶️Answer/Explanation
Ans: A
All the outer shell electrons are used here to form covalent bonds.
In B, C and D, Cl, O and N have unshared outer shell electrons as lone pair.
Question
Which substance is a diatomic covalent compound?
A \(Cl_2\) B HCl C \(H_2O\) D MgO
▶️Answer/Explanation
Ans: B
In \(Cl_2\) , single type of Cl atoms combine.
In HCl, two different type of H and Cl atoms combine to form this diatomic covalent compound.
MgO is ionic compound.
Question
Which statement about carbon is correct?
A Diamond and graphite both have simple molecular structures.
B Diamond and graphite are both used to make cutting tools.
C Each carbon atom in diamond is bonded to three other carbon atoms.
D Graphite conducts electricity and has a giant covalent structure.
▶️Answer/Explanation
Ans: D
Graphite is a soft, black, and slippery material. It consists of carbon atoms arranged in layers of interconnected hexagonal rings. Within each layer, carbon atoms are bonded together through strong covalent bonds, forming a two-dimensional sheet. However, the layers are held together by weak van der Waals forces, allowing them to easily slide past each other. This gives graphite its characteristic lubricating and soft properties. Graphite is an excellent conductor of electricity due to the presence of delocalized electrons within the layers.
Diamond is a hard, transparent, and crystalline substance. It consists of carbon atoms arranged in a three-dimensional lattice structure. Each carbon atom forms strong covalent bonds with four neighboring carbon atoms, resulting in a rigid and tightly bound network. The arrangement of carbon atoms in diamond gives it exceptional hardness, making it one of the hardest known substances. Diamond also has a high melting point and is a good thermal conductor. It does not conduct electricity well due to the absence of free electrons or ions.
Question
Ammonia, \(NH_3\), is a covalent molecule.
Which diagram shows the outer shell electron arrangement in a molecule of ammonia?
▶️Answer/Explanation
Ans: C
C is the correct arrangement. N has a lone pair and 3 N-H bond pairs in ammonia.