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CHEMICAL FORMULAS

CHEMICAL FORMULAS. Chemical Formulas. A chemical formula provides the clearest and simplest method of designating compounds. It indicates the number and kind of elements present in the compound. Compounds that consist of two elements are called binary compounds. Binary Compounds. AlCl 3

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CHEMICAL FORMULAS

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  1. CHEMICAL FORMULAS

  2. Chemical Formulas • A chemical formula provides the clearest and simplest method of designating compounds. • It indicates the number and kind of elements present in the compound. • Compounds that consist of two elements are called binary compounds.

  3. Binary Compounds • AlCl3 • NaCl • MgO • CO2 • LiH

  4. General Rules for Oxidation Numbers • Charge on pure elements is _______. • All metals of Group IA are ________. • All metals of Group IIA are _______. • The charge on all elements in GroupIIIA is _____ except Tl which can also be ____. • The charge on hydrogen is ___or __. • The charge on fluorine is ____.

  5. General Rules for Oxidation Numbers 7. Other halogens (VIIA) are ____ except when combined with oxygen. Then they are +. 8. Group IVA elements are ___ when negative. 9. Group VA elements are ____ when negative. 10. Group VIA elements are ___ when negative.

  6. Polyatomic Ions Memory Work • Ammonium_______ Cyanide_________ • Acetate__________ Carbonate_______ • Nitrate__________ Sulfate__________ • Hydroxide_______ Phosphate________

  7. Writing Formulas of Compounds 1. Write the symbol for the positive element first. • The element name with the ending changed to -ide indicates the element with a negative oxidation number.

  8. Writing Formulas of Compounds • Examples: • Oxide = ________ telluride = ________ • Chloride = ______ hydride = ________ • __________ = S2- __________ = P3-

  9. Writing Formulas of Compounds • Use subscripts to make the formula contain the number of atoms required for a neutralformula unit. Example: sodium chloride Na1+ Cl1- 1+1- = 0 NaCl

  10. Writing Formulas of Compounds • calcium chloride sodium oxide

  11. Writing formulas of compounds • Magnesium nitride potassium hydride

  12. Writing formulas of compounds • If more than one polyatomic ion appears in the formula put the polyatomic ion in parentheses. Example: potassium nitrate

  13. Writing formulas of compounds • Magnesium nitrate

  14. Writing formulas of compounds • If a Roman numeral appears after the name of the positive element, this number indicates the oxidation number of the positive element. Example: tin (IV) chloride

  15. Naming Binary Compounds • State the name of the positive element first. • State the name of the negative element and change the ending to -ide. • NaCl sodium chloride • CaS _____________

  16. Naming Binary Compounds • If the positive element can have morethan one positive oxidation number use the stock system: • Stock System- Put a Roman numeralin parentheses after the name of the positive element to show its oxidation number.

  17. Naming Binary Compounds • CuCl2 • Note: Do not use the Stock System if only one positive oxidation number is possible.

  18. Naming Compounds that contain Polyatomic Ions • Write the name of the positive element first. • If the positive element has more than one possible oxidation number use the stock system. • The names and formulas of polyatomic ions are generally to be memorized.

  19. Examples

  20. Greek Prefix System • An older system of nomenclature is often used, especially for compounds containing only nonmetals. • Greek prefixes are used to tell how many atoms are present in the formula.

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