# Writing Formulas and Naming Compounds Atoms and molecules react with one another to become more stable. Atoms become more stable by either gaining/losing.

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Writing Formulas and Naming Compounds Atoms and molecules react with one another to become more stable. Atoms become more stable by either gaining/losing electrons so that they have 8 valence electrons (full outer energy level). Na1s 2 2s 2 2p 6 3s 1 1 valence electron Cl1s 2 2s 2 2p 6 3s 2 3p 5 7 valence electrons

Sodium will lose 1 e- to get 8 valence electrons (a noble gas configuration). Chlorine will gain 1e- to get 8 valence e- (a noble gas configuration). Na  Na +1 + 1e- Cl + 1e-  Cl -1 Na +1 + Cl -1  NaCl The Na +1 and Cl -1 ions have very different properties than the Na and Cl atoms.

Atoms form ions by gaining or losing electrons. The metals tend to lose electrons (positive ions), the nonmetals tend to gain electrons (negative ions). The position of the element on the periodic table can help determine how many valence electrons the atom has, and what charge it will probably have when it becomes an ion.

Groups and Ion Charges Group Valence e- Gain/Lose e- Ion charge 11 Lose 1 +1 22 Lose 2 +2 133 Lose 3 +3 144Tweener+4/-4 155 Gain 3 -3 166 Gain 2 -2 177 Gain 1 18800

Ions are atoms with different numbers of protons and electrons. They are formed by either gaining or losing electrons. If an atom loses electrons, it has more protons than electrons and becomes positively charged. This is called a cation, and usually happens to the metals. If an atom gains electrons, it has more electrons than electrons and becomes negatively charged. This is called an anion, and usually happens to the nonmetals.

Monatomic Ions – an ion made up of only one type of atom (H +1, Ca +2, S -2, Cl -1, …) Polyatomic Ions – an ion made up of two or more different types of atoms (NO 3 -1, OH -1, SO 4 -2, NH 4 +1, …) The compound Na 3 PO 4 is made up of 3 monatomic ions (Na +1 ) and 1 polyatomic ion (PO 4 -3 ).

Ions are named differently than elements because they have different properties. In General Metals – the word ion is added after the name of the element. Na = sodiumNa +1 = sodium ion Nonmetals – the ending of the element is dropped, and –ide is added. Br = bromineBr -1 = bromide O = oxygenO -2 = oxide

Ionic compounds are made from ions combining. The compound has no net charge, or is neutral, even though it is made up of both positive and negative ions. Naming compounds and writing formulas is easy if you know the names, charges and formulas of all of the ions on the ion list. If you don’t know these, you will be guessing on all of your names or formulas.

Polyatomic Ions FormulaName NH 4 +1 Ammonium NO 3 -1 Nitrate ClO 3 -1 Chlorate OH -1 Hydroxide C 2 H 3 O 2 -1 Acetate SO 4 -2 Sulfate CO 3 -2 Carbonate PO 4 -3 Phosphate

Elements with more than one charge NameSymbolNameSymbol Copper (I) Cu +1 Copper (II) Cu +2 Chromium (II) Cr +2 Chromium (III) Cr +3 Manganese (II) Mn +2 Manganese (III) Mn +3 Cobalt (II) Co +2 Cobalt (III) Co +3 Iron (II) Fe +2 Iron (III) Fe +3 Nickel (II) Ni +2 Nickel (III) Ni +3 Tin (II) Sn +2 Tin (IV) Sn +4 Lead (II) Pb +2 Lead (IV) Pb +4

Naming Ionic Compounds Give the name of the positive ion, cation, including the roman numeral if appropriate followed by the name of the negative ion, anion. Names of the cation are the same as the name of the element. Names of monatomic anions usually end with -ide. Names of polyatomic anions usually end with –ate.

NaClsodium chloride LiNO 3 lithium nitrate CuClcopper (I) chloride CuCl 2 copper (II) chloride Sr(ClO 3 ) 2 strontium chlorate MgOmagnesium oxide CaSO 4 calcium sulfate FeBr 3 iron (III) bromide

Writing correct ionic formulas Write the cation followed by the anion Write the cation followed by the anion Cross the numerical charges to become the subscripts. Drop all +/- signs Cross the numerical charges to become the subscripts. Drop all +/- signs If the subscripts are 1, do not write the 1. If the subscripts are multiples, reduce them. If the subscripts are 1, do not write the 1. If the subscripts are multiples, reduce them. If more than one polyatomic ion is needed, put ( ) around the polyatomic ion before adding the subscript. If more than one polyatomic ion is needed, put ( ) around the polyatomic ion before adding the subscript.

Ionic Compounds Made up of positive and negative ions Made up of metals and nonmetals “Salts” Will conduct electricity when dissolved in water Electrons are transferred between atoms Opposites attract Positive ion always comes first

Covalent Compounds Made up of two or more nonmetals Electrons are shared between atoms Do not conduct electricity in water No ions are present

Prefixes PrefixMeaningPrefixMeaning Mono-1Hexa-6 Di-2Hepta-7 Tri-3Octa-8 Tetra-4Nona-9 Penta-5Deca-10

Naming covalent compounds Give the prefix telling how many of the first element (except mono-), then give the name of the first element. Give the prefix telling how many of the first element (except mono-), then give the name of the first element. Give the prefix telling how many of the second element, then give the name of the second element ending with –ide. Give the prefix telling how many of the second element, then give the name of the second element ending with –ide. P 2 O 5 COCO 2 N 2 O 4 P 2 O 5 COCO 2 N 2 O 4 PCl 3 ICl 3 SiO 2 N 4 Cl 7 PCl 3 ICl 3 SiO 2 N 4 Cl 7

Naming Acids: HX, H 2 X, H 3 X If the anion X ends in –ide If the anion X ends in –ide hydro (name of anion, drop the ending) –ic acid hydro (name of anion, drop the ending) –ic acid HCl hydro chloric acid HBr hydrobromic acid H 2 O hydro oxic acid H 2 S hydro sulfuric acid If the anion X ends in –ate If the anion X ends in –ate (name of the anion, drop the ending)-ic acid (name of the anion, drop the ending)-ic acid HNO 3 nitric acid H 2 SO 4 sulfuric acid HClO 3 chloric acid HC 2 H 3 O 2 acetic acid

Names and formulas of common acids H 2 SO 4 H 2 SO 4 HCl HCl HNO 3 HNO 3 HC 2 H 3 O 2 HC 2 H 3 O 2 H 3 PO 4 H 3 PO 4 Sulfuric Acid Sulfuric Acid Hydro chloric acid Hydro chloric acid Nitric acid Nitric acid Acetic acid Acetic acid Phosphoric Acid Phosphoric Acid

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