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Question Video: Determining the Chemical Formula of Sodium Chloride Science

The salt, sodium chloride, can be formed from the reaction between an acid and an alkali. What is the chemical formula of sodium chloride?

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Video Transcript

The salt, sodium chloride, can be formed from the reaction between an acid and an alkali. What is the chemical formula of sodium chloride?

A chemical formula is an expression of chemical symbols and numerical subscripts that represents the composition of a molecule or one unit of a compound. An example of a chemical formula is H2O. Capital H is the chemical symbol of hydrogen, and capital O is the chemical symbol of oxygen. The subscript two after hydrogen means that there are two atoms of hydrogen in one molecule of H2O. When no value is written, only one atom of that element is present in the molecule or unit.

To answer this question, we need to determine the chemical formula of a compound from its name. In order to write a chemical formula from a name, we need to know two key pieces of information. We need to identify what elements the compound contains and also what type of compound it is, covalent or ionic. We can determine what elements the compound contains by looking at the name and the periodic table.

Sodium is a metallic element found in the first column of the periodic table. The name chloride doesn’t appear on the periodic table exactly as written. This is because when compounds are named, the end of the second element name is changed to I-D-E. So the name chloride represents the element chlorine, a nonmetal found in column 17 of the periodic table. We can see that sodium chloride is a compound formed when a metal and a nonmetal combine. In addition, when we look at the name, no prefixes appear in front of sodium or chloride. This all points to sodium chloride being an ionic compound.

Now we’re ready to write the chemical formula of sodium chloride, an ionic compound. First, we’ll write the chemical symbol and valence for each element in the compound. We can determine the valence of many elements by looking at the periodic table. Sodium in column one has a valence of one. Chlorine in column 17 also has a valence of one. Next, we crisscross the valence values writing each valence value as a subscript to the right of the opposite chemical symbol. This gives us Na1Cl1. But ones in a chemical formula don’t have to be written. So, the chemical formula of sodium chloride is NaCl.

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