Aword element at the end of the roots that changes or adds to its meaning is a(n)

A word element at the end of the root that changes or adds to its meaning is a suffix.

Like prefixes, suffixes are a type of affix. This means that when added to a word base, they create a derivative or inflectional form of this word, with a new meaning.

For example,

adding the suffix -ly to an adjective makes it an adverb (commercial - commercially);adding the suffixes -able or -ible to a verb makes it an adjective which means "fit or liable to be ..." (break - breakable)

Ifound the exercise on the internet. attached is the list mentioned above.in order for a compound to be considered optically active it can't have any axis or plan of symmetry. the molecule  shouldn't also  be superimposable on its mirror image.with such considerations, the compounds that are optically active are: -third compound on the first image is optically active; -second and third compound from the second image are optically actives.