Counting Atoms

Front

What is an element?

Back

An element is a pure substance that cannot be broken down into simpler substances by chemical means. Each element is made up of atoms that have the same number of protons.

Front

How do you determine the number of different elements in a chemical formula?

Back

Count the unique symbols in the formula. Each symbol represents a different element.

Front

What does the subscript in a chemical formula indicate?

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

Front

What is a compound?

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A compound is a substance formed when two or more elements chemically bond together in a fixed ratio.

Front

How many atoms are in a molecule of H2O?

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A molecule of H2O contains 3 atoms: 2 hydrogen atoms and 1 oxygen atom.

Front

What is the significance of parentheses in chemical formulas?

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Parentheses indicate that the atoms inside them are grouped together and may be multiplied by a subscript outside the parentheses. For example, in Ca(OH)2, the '2' applies to both O and H.

Front

How many oxygen atoms are in Mg(NO3)2?

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There are 6 oxygen atoms in Mg(NO3)2. Each nitrate (NO3) has 3 oxygen atoms, and there are 2 nitrates.

Front

What is the formula for calculating the total number of atoms in a compound?

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Add the number of atoms of each element together, considering their subscripts. For example, in C3H8, there are 3 carbon atoms and 8 hydrogen atoms, totaling 11 atoms.

Front

What does the term 'molecular formula' mean?

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A molecular formula shows the number and type of atoms in a molecule, but not how they are arranged. For example, C6H12O6 is the molecular formula for glucose.

Front

How do you identify the number of sulfur atoms in Al2(SO4)3?

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There are 3 sulfur atoms in Al2(SO4)3. The sulfate (SO4) group contains 1 sulfur atom, and there are 3 sulfate groups.