When atoms share one or more electrons in their outer electron shells in order for each to complete its own shell, a covalent bond is formed between the atoms. The more electrons shared, the stronger the bond. The atoms of some elements always have a complete outer shell of electrons. These elements are said to be inert, meaning that they do not react with other elements to form compounds. Most covalent compounds are gases or liquids at room temperature. Oxygen, hydrogen, and nitrogen are examples of elements usually found in a covalent compound.
What can you infer from the information?
It is common knowledge that oxygen, hydrogen, and nitrogen are among the most abundant elements in nature. These elements are usually found bonded with elements by covalence, which means that they have reacted with other elements to form covalent bonds.