Molecules and Ions
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