The mole is defined as a specific number (6.02 × 1023) of entities. There is more than one type of chemical entity.
The atom is the chemical entity for elements represented by the symbol for the element.
Many common nonmetallic elements exist as molecules.
Molecules are uncharged entities discrete groups of atoms joined by chemical bonds.
The number of chemical entities in samples of molecular substances depends on which entity is specified.
Amount in moles can be used to describe either the number of atoms OR the number of molecules.
The amount in moles of specified atoms in a molecular substance is the number of atoms times the given amount in moles.
The atom is the chemical entity for elements represented by the symbol for the element.
Examples of elments represented by the symbol for the element are He, Cu and C. As shown in the diagrams these substances exist as isolated atoms (He) or infinite lattices (Cu or C) where every atom is equivalent to every other atom.
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Many common nonmetallic elements exist as molecules.
Molecules are uncharged entities discrete groups of atoms joined by chemical bonds.
Elemental hydrogen exists as diatomic (two-atom) molecules (represented by H2). The diagram represents a very small sample of hydrogen gas.
The number of chemical entities in samples of molecular substances depends on which entity is specified.
There are 10 H2 molecules in the sample of hydrogen shown.
There are 20 H atoms (each molecule has 2 atoms joined by a chemical bond).
There are 20 H atoms (each molecule has 2 atoms joined by a chemical bond).
Amount in moles can be used to describe either the number of atoms OR the number of molecules.
1 mol of elemental hydrogen (H2) has 6.02 × 1023 H2 molecules.
1 H2 molecule has 2 H atoms.
1 mol of elemental hydrogen (H2) has 2.0 mol H atoms.
1 H2 molecule has 2 H atoms.
1 mol of elemental hydrogen (H2) has 2.0 mol H atoms.
The amount in moles of specified atoms in a molecular substance is the number of atoms times the given amount in moles.
This can be expressed mathematically using n as the symbol for amount in moles.
amount in moles of H atoms = n(H) = 2 × n(H2) = 2 × amount in moles of H2 molecules
amount in moles of H atoms = n(H) = 2 × n(H2) = 2 × amount in moles of H2 molecules