Which of the following statements is true regarding the Lewis structure for methylamine, CH3NH2?

a) There will be an unshared pair of electrons on the nitrogen atom.
b) There will be three covalent bonds to the carbon.
c) Nitrogen will form a double bond with the adjacent carbon.
d) Both a and c are correct.
e) All of the above are correct.

H

|
HC-H
|
HNH
..

a is true.
b is not true; there are 4 covalent bonds to C.
c is not true. There is no double bond.
d and e can't be right

The correct statement regarding the Lewis structure for methylamine, CH3NH2, is a) There will be an unshared pair of electrons on the nitrogen atom.

In the Lewis structure of methylamine, the nitrogen atom shares three of its valence electrons with hydrogen atoms, forming three covalent bonds. The remaining electron on nitrogen is not shared with any other atom and is considered as an unshared pair of electrons. Therefore, option a) is the correct statement.

To determine which statement is true regarding the Lewis structure for methylamine, CH3NH2, let's analyze the structure of the molecule.

To draw the Lewis structure of methylamine, we first need to determine the total number of valence electrons for all the atoms in the molecule. Carbon has 4 valence electrons, hydrogen has 1 valence electron, and nitrogen has 5 valence electrons. Since there are three hydrogen atoms and one nitrogen atom in the molecule, the total number of valence electrons is:

(4 carbon valence electrons) + (1 nitrogen valence electrons) + (3 hydrogen valence electrons) = 4 + 5 + 3 = 12 valence electrons.

To distribute the electrons in the Lewis structure, we start by connecting the atoms with single bonds. Carbon will bond to each hydrogen atom, and nitrogen will bond to carbon. This gives us the following structure:

H H

H─C─N

H

After using three pairs of electrons for the single bonds (1 pair for each bond), we have 9 valence electrons remaining.

Next, we need to fulfill the octet rule for each atom, except for hydrogen, which only needs 2 electrons to complete its outer shell. Carbon already has a full octet, as it has 8 electrons surrounding it. Nitrogen, on the other hand, still requires an additional electron to complete its octet.

To provide this additional electron to nitrogen, we can take one pair of electrons (2 electrons) and form another bond between carbon and nitrogen. This gives us the following structure:

H H

H─C─N
│ │
H H

After using a pair of electrons to form the additional bond, we have 7 valence electrons remaining.

At this point, we can distribute the remaining electrons as unshared pairs to fulfill the octet rule for nitrogen. This leaves us with the final structure:

H H
│ │
H─C─N─H
│ │ │
H H H

From the Lewis structure of methylamine, we can conclude that statement a) "There will be an unshared pair of electrons on the nitrogen atom" is true.

Therefore, the correct answer to the question is option a) "There will be an unshared pair of electrons on the nitrogen atom."