AP BIOLOGY

Detailed explanation-1: -A water molecule has three atoms: two hydrogen (H) atoms and one oxygen (O) atom. That’s why water is sometimes referred to as H2O.

Detailed explanation-2: -A compound is a substance that contains two or more elements chemically combined in a fixed proportion. The elements carbon and hydrogen combine to form many different compounds.

Detailed explanation-3: -Water is a compound composed of atoms of two elements, hydrogen and oxygen, bonded together. A molecule of water is composed of two hydrogen atoms (H) and one oxygen atom (O). This relationship is expressed in the chemical formula for water, H2O (Fig. 1.4).

Detailed explanation-4: -To find out what water is made of, it helps to look at its chemical formula, which is H2O. This basically tells us that the water molecule is composed of two elements: hydrogen and oxygen or, more precisely, two hydrogen atoms (H2) and one oxygen atom (O).

Detailed explanation-5: -Oxygen is a chemical element – a substance that contains only one type of atom. Its official chemical symbol is O, and its atomic number is 8, which means that an oxygen atom has eight protons in its nucleus.