Final answer:
The name of elements in a compound is distinguished from their free state by using numerical prefixes to indicate the number of atoms and modifying the second element's name with an -ide suffix, like in carbon dioxide for CO₂.
Step-by-step explanation:
When elements combine to form compounds, the naming convention differs from the names of the uncombined elements. The answer to the question about how the name of the elements in each compound differs from that of the free elements, before combining, is that elements in compounds are given numerical prefixes (option c) to indicate the number of atoms of each element present in the compound, and the second element's name is modified with the suffix -ide. For example, the compound consisting of carbon and oxygen with one carbon atom and two oxygen atoms is named carbon dioxide (CO₂), where the 'di-' prefix indicates two oxygen atoms.
The naming process involves arranging the elements based on their position in the periodic table, with the more metallic element (left and/or bottom) named first. If there are multiple atoms of an element, numerical prefixes like mono-, di-, tri-, and tetra- are used, except that no prefix is added to the first element's name if there is only one atom of it. Special exceptions exist such as compounds containing hydrogen where hydrogen is usually listed first, exemplified by the name dihydrogen monosulfide for H₂S.