Molecules and Ions

Chemical bonds Atoms are held together in compounds by chemical bonds

Covalent Bonds If atoms are held together by sharing electrons then this is known as a chemical bond Covalent bonds form molecules Molecules are represented by chemical formulas, H2O Or by structural formulas, H – O – H Or by models

Ionic Bonds If electrons are transferred then an ionic bond is formed NaCl Na  Na+ + e- Cl + e  Cl-

Periodic Table Lots of info Charge Atomic Mass Atomic Number Metals and Non-Metals Alkali Metal (I), Alkali Earth Metals (II), Halogens (VII), Noble Gases (VIII), Trans. Met.

Periods Horizontal rows on PT

Groups Columns on PT

Naming Simple Compounds Binary Compounds These are compounds that are composed of two types elements

Binary Ionic Compounds (Type I) These compounds contain a positive ion (cation) and a negative ion (anion) Na+, cation Cl-, anion

Rules for Naming Type I Binary Ionic Compounds Cation always named first Anion always named second A monoatomic cation is named as the element is named, Na+ is sodium A monoatomic anion is named as the element but as an –IDE, so Cl- is ChlorIDE See Table 2.3

Name These CsF Cesium Flouride AlCl3 Aluminum chloride LiH Lithium Hydride

Binary Ionic Compounds (Type II) Many cations can form more than one type of ions Especially the Transtition Metals Use Roman Numerals to indicate charge Ion of higher charge ends in –ic Ion of lower charge end in –ous Fe (II) ferrous, Fe(III) ferric

Naming Type II Binary Compounds CuCl Copper (I) chloride HgO Mercury (I) oxide Fe2O3 Iron (III) oxide

Write the formula for these Manganese (IV) oxide MnO2 Lead (II) chloride PbCl2

If the cation only has one possible ion thenn DO NOT USE a roman numeral It is understood what the charge on the ion is

Polyatomic Ions Some ions are made up of two or more atoms These are known as polyatomic ions SO4 -2, OH-, NO3- See Table 2.5 Must know formula and charge Use flashcards

Name these compounds Na2SO4 Sodium sulfate KH2PO4 Potassium dihydrogen phosphate Na2CO3 Sodium carbonate

WriteFormulas Sodium Hydrogen Carbonate NaHCO3 Potassium perchlorite KClO4

Binary Covalent Compounds (Type III) These are compounds formed between two non-metals

Rules for Naming Binary Covalent Compounds (Type III) The first element in the formula is named first The second is named as if it was an anion Prefixes denote the number of atoms present Mono- is never used for the first element as it is assumed. Mono- is used for the second element, Co See p. 63

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