a)
Identify the central atom.
The central atom is N.
Determine the number of valence electrons around the central atom.
Nitrogen has 5 valence electrons. It forms three bonds with three methyl groups (CH3), contributing 3 electrons. The two dots represent a lone pair, contributing another 2 electrons. In total, the nitrogen atom has 5 + 3 + 2 = 8 electrons in its octet.
Determine if the central atom can accept electrons.
The nitrogen atom has a complete octet. The lone pair can be donated.
Classify the molecule.
The nitrogen atom can donate its lone pair. Thus, the molecule is a Lewis base.
\(\boxed{\text{Lewis base}}\)
b)
Identify the charged atom.
The charged atom is the carbon atom bonded to the methyl group.
Determine the number of valence electrons around the charged atom.
Carbon has 4 valence electrons. It makes 3 bonds with 3 carbon atoms of the ring, contributing 3 electrons. There is a positive charge, so it has lost one electron. The total count of electrons around carbon is 4 - 1 + 3 = 6. It lacks 2 electrons from a full octet.
Determine if the charged atom can accept electrons.
The positively charged carbon can accept electrons to complete its octet.
Classify the ion.
The charged carbon atom can accept electrons, making this ion a Lewis acid.
\(\boxed{\text{Lewis acid}}\)
c) $\mathrm{FeCl}_{3}$
Identify the central atom.
The central atom is Fe.
Determine the typical charge on the central atom.
Transition metals like Fe can have various oxidation states. In $\mathrm{FeCl}_{3}$, Cl has a -1 charge and there are three of them, hence Fe carries a charge of +3.
Determine if the central atom can accept electrons.
Fe in +3 state has empty orbitals and can accept electrons.
Classify the molecule.
The Fe atom can accept electrons. Thus, the molecule is a Lewis acid.
\(\boxed{\text{Lewis acid}}\)
\(\boxed{\text{a) Lewis base}}\)
\(\boxed{\text{b) Lewis acid}}\)
\(\boxed{\text{c) Lewis acid}}\)
Answered
