The -ium suffix is a Latin suffix which forms abstract nouns, thus it is used to form chemical elements' name from its naming origin, such as minerals (calcium from calx) or person names (gadolinium). To confirm and add a reference to the other two answers.

What does the suffix ium means?

-ium, a suffix found on nouns borrowed from Latin, esp. ... millennium), and derivatives of personal nouns, often denoting the associated status or office (collegium; consortium; magisterium);

How many elements end in the suffix ium?

There are 81 elements (grey) that end in the suffix –ium or –um, which is derived from Latin and denotes a metallic substance.