How to Write Zinc Sulfate
To write the formula for zinc sulfate, it is first necessary to know what it is. Zinc sulfate is a compound of zinc, sulfur and oxygen. If it has not been oven-dried, it will contain "water of crystallization." Zinc, sulfur, oxygen and hydrogen (from the water) are all elements. The smallest particle of an element is called an atom. Atoms combine to form molecules. Zinc sulfate exists as molecules. Although molecules are built up of charged atoms, there is no overall or net charge to them. Knowing this makes it possible to write the formula for zinc sulfate.
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Instructions
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Learn the shorthand symbol for zinc. The chemical symbol for Zinc is Zn. Compounds are held together because of electrical charges. Zinc forms "ions" with a charge of plus two. This is because zinc loses two electrons, each with a minus one charge, when forming compounds. Zinc ions are written as Zn⁺². When writing compounds, however, it is not customary to include charges unless there is a special reason to do so, since compounds have all their charges balanced out, so that they are neutral.
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Learn the symbol for sulfur and oxygen, which are S and O, respectively. Sulfur can have a variety of valences, a term which refers to how many electrons can be easily lost or gained by an atom when forming compounds. There are at least three different valences for sulfur. Oxygen's valence is minus two. Sulfate's formula is SO₄⁻². Since oxygen is minus two and there are four of them, that adds up to minus eight. But the overall charge is only minus two. Sulfur in sulfate has a valence of plus six.
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Determine the formula for water. Hydrogen's symbol is H. Hydrogen has a valence of plus one. Everyone knows the formula for water is H₂O. This is because oxygen minus two requires two atoms of hydrogen plus one to balance the charges.
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Write zinc sulfate's formula. Since zinc has a plus two and sulfate has a minus two, the charges cancel when the formula for zinc sulfate is ZnSO₄. There is no easy way to know the formula for zinc sulfate plus water of crystallization. Chemistry books reveal there are seven waters of crystallization.
Write down the formula for hydrated zinc sulfate: ZnSO₄·7H₂O. The correct name for this structure is zinc sulfate heptahydrate.
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Tips & Warnings
Oregon State University's Valley Library provides a special collection of lecture videos on the topic of valence by Nobel Prize winner Linus Pauling (see Resources).
