Answer:
Element; compound
Explanation:
Oxygen is an element on the periodic table, but when it's combined with the element Hydrogen, it produces water, which is a compound (H2O). When two elements combine, it produces a compound.
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A specific combination of bonded atoms which always react in the same way, regardless of the particular carbon skeleton is known as the functional group. These are specific groups of atoms or bonds within organic molecules that accounts for the characteristic chemical reactions of those molecules. Examples of functional groups are the Carbonyl group, alkyl Halides, aldehydes and ketones among others.
Acetic acid, phosphoric acid, hydrochloric acid.
sodium bicarbonate, magnesium hydroxide, aluminum hydroxide
calcium carbonate, sodium bicarbonate, magnesium sulfate.