Molecules and Ions. Chemical bonds Atoms are held together in compounds by chemical bonds

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

• Review