Final answer:
To interpret chemical formulas with parentheses, use the subscript outside the parentheses as a multiplier for each atom in the polyatomic ion within. Subscripts indicate quantity, not arrangement, and cannot be changed to balance chemical equations, where coefficients are used instead.
Step-by-step explanation:
Understanding Chemical Formulas with Parentheses
To understand all chemical formulas including those with parentheses, it's essential to recognize that parentheses are used to indicate polyatomic ions or groups of atoms within a compound that repeat multiple times. When a polyatomic ion is represented in a formula, if there is more than one ion, the entire formula for the ion is enclosed in parentheses with a subscript following the closing parenthesis. This subscript acts as a multiplier for each atom within the ion.
For example, the formula for calcium nitrate is written as Ca(NO3)2. Here, the polyatomic ion nitrate (NO3-) appears twice in the compound, so the entire ion formula is enclosed in parentheses with a subscript 2 outside to indicate the quantity. To count atoms, you simply multiply the number of atoms within the parentheses by the subscript number. Thus, this compound contains one calcium atom, two nitrogen atoms, and six oxygen atoms (1 Ca, 2 N, 6 O).
Another key detail is to understand that the subscript affects only the atoms within the parentheses. Also, remember that molecular formulas provide the type and number of atoms in a molecule but do not describe the structure or arrangement of atoms.
When balancing chemical equations, keep in mind that you cannot change subscripts to balance but instead place coefficients before the formulas. For example, if an ionic compound like calcium nitrate reacts, you'd write the component ions and balance the equation using coefficients—not by altering subscripts.
Additionally, physical states can be indicated with symbols such as (s) for solid, (l) for liquid, (g) for gas, and (aq) for aqueous solutions directly after the chemical formula, but these do not affect how the formulas are interpreted.