Counting Atoms in Chemical Formulas

Front

What is a chemical formula?

Back

A chemical formula is a way of expressing the number and type of atoms in a molecule using element symbols and subscripts.

Front

What does a subscript in a chemical formula indicate?

Back

A subscript indicates the number of atoms of the element in the molecule. For example, in H2O, the '2' indicates there are two hydrogen atoms.

Front

How do you determine the number of atoms in a compound with parentheses?

Back

Multiply the subscript outside the parentheses by the subscripts of each element inside. For example, in (NO3)2, there are 2 nitrogen and 6 oxygen atoms.

Front

What is the difference between a coefficient and a subscript?

Back

A coefficient indicates the number of molecules, while a subscript indicates the number of atoms in a molecule.

Front

How many oxygen atoms are in 4H2SO4?

Back

There are 16 oxygen atoms (4 x 4 = 16) in 4H2SO4.

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What does it mean if there is no subscript next to an element in a chemical formula?

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If there is no subscript, it means there is only 1 atom of that element in the molecule.

Front

How many total atoms are in C3H5(NO3)3?

Back

There are 21 total atoms: 3 Carbon, 5 Hydrogen, 3 Nitrogen, and 9 Oxygen.

Front

What is the formula for a compound containing 2 sodium (Na), 1 sulfur (S), and 4 oxygen (O) atoms?

Back

The formula is Na2SO4.

Front

What is the significance of the number in front of a chemical formula?

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The number in front of a chemical formula (coefficient) indicates how many molecules of that compound are present.

Front

How many hydrogen atoms are in the formula C2H6?

Back

There are 6 hydrogen atoms in C2H6.