Final answer:
A group of two or more atoms chemically bonded together is called a molecule. If the atoms are of the same type, it's simply a molecule, like H2, while if they are of different types, such as in H2O or CH4, the substance is both a molecule and a compound.
Step-by-step explanation:
A group of 2 or more atoms (either the same or different type) chemically bonded together is known as a molecule. When these atoms are chemically bonded, they form a more or less stable grouping that is generally less reactive than the separate atoms. An example of a molecule comprising the same type of atoms is H2, also known as molecular hydrogen or hydrogen gas. However, when the molecule consists of different types of atoms, it is referred to as a compound, such as H2O (water), which consists of hydrogen and oxygen atoms bonded together, or CH4 (methane), which is composed of carbon and hydrogen atoms. Therefore, the correct answer to the student's question is option 1: A molecule.