A molecule of ethylamine is made up of two carbon atoms, seven hydrogen atoms, and one nitrogen atom. (a) Write its molecular formula. (b) The reactive group in ethylamine is \(\mathrm{NH}_{2}\). Write its condensed structural formula.

Based on the information given in the exercise, we determine the molecular formula by listing the total number of atoms of each element present in the molecule. Since ethylamine consists of two carbon atoms, seven hydrogen atoms, and one nitrogen atom, its molecular formula can be represented as \(\mathrm{C}_{2}\mathrm{H}_{7}\mathrm{N}\). (a) The molecular formula of ethylamine is \(\mathrm{C}_{2}\mathrm{H}_{7}\mathrm{N}\).

To represent the condensed structural formula, we need to connect the atoms in the molecule, keeping in mind the reactive group \(\mathrm{NH}_{2}\). Ethylamine consists of two carbon atoms which are bonded as an ethyl group (with single bonds) with attached hydrogen atoms. The first carbon atom is bonded to three hydrogen atoms, and the second carbon atom is bonded to two hydrogen atoms. The nitrogen atom in the reactive group \(\mathrm{NH}_{2}\) is attached to the second carbon atom in the ethyl group, with two hydrogen atoms bonded to it. The condensed structural formula can be written as follows: \(\mathrm{CH}_{3}\mathrm{CH}_{2}\mathrm{NH}_{2}\) (b) The condensed structural formula of ethylamine is \(\mathrm{CH}_{3}\mathrm{CH}_{2}\mathrm{NH}_{2}\).