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Chapter 2Part B
Molecules and Molecular Compounds 2.6
• Only rare gases (8A) naturally found as isolated atoms
• Rest of matter exists as molecules or
ions
Chemical Formulas 2.6
• Diatomic molecules:– H2, O2, N2, F2, Cl2, Br2, I2
Molecular Compounds 2.6
• Compounds composed of molecules with >1 type of atom
Most molecular substances composed of non-metals
Chemical formula
Molecular and Empirical Formulas 2.6
• Molecular formula: Chemical formula with actual number of atoms in a molecule
• Empirical formula: chemical formula with relative number of each type of atom in a molecule (smallest whole number subscripts)
Molecular formula Empirical FormulaC4H10 CH5
H2O H2O
H2O2 HO
Structural Formula 2.6
• 2D:• Shows composition AND attachment of atoms• 3D:• Perspective structural formula
– Uses elemental symbols
• Ball and stick structural formula– Different color = different atom
• Space filing model – Different color = different atom
Ions and Ionic Compounds 2.7
• Typically the nucleus (+ and °) is unchanged by chemical reactions
• Gain or loss of electrons (-) produces:– CATions + loss of electrons– ANions – gain of electrons
Formation of a Cation 2.7
Na: atomic number 11 Na+: 11 protons and 10 electrons = loss of 1 electron
Formation of an Anion 2.7
Cl: atomic number 17 Cl-: 17 protons and 18 electrons = loss of 1 electron
Generally 2.7
• Metals - electron cations• Nonmetals + electron anions• Therefore ionic compounds are
metal:nonmetal
• *Chemical properties of ions are very different from chemical properties of parent atom (just from the loss of a few – charges)*
Why Do Atoms Ionize? 2.7
• Atoms prefer to gain/lose electrons in order to have the same amount of electrons as their nearest noble (inert) gas– = stability!
Simple Ion Rules 2.7
Ionic Compounds 2.7• Cations + anions• Metal element + non-metal element• (Metal ion + non-metal ion)• Very strong chemical bond• Must be electrically neutral formula
– Careful with charges and subscripts!
Nomenclature of Inorganic Compounds 2.8
• 50,000,000 + chemical substances known!– Therefore only some have common names
Therefore we have a system for naming…
– *memorizing and naming PRACTICE are only way*
Inorganic Compounds-Cations 2.8
– 1—Cations: name of metal atom + ion• A. One cation only: Al3+ = aluminum ion
– *Metals from groups IA, IIA, Al, Ag+ and Zn2+*
• B. several cations: Fe2+ = iron (II) ion; ferrous ion
(different properties)Fe3+ = iron (III) ion; ferric ion– *typically transition metals*
Inorganic Compounds-Cations (cont) 2.8
– C. cation formed from nonmetal atoms• NH4
+ ammonium ion
• H3O+ hydronium ion
Anions 2.8
• 2--anions:
(A. Mono and some polyatomic)
(B. Most polyatomic)
1 23 4
Oxyanions (cont) 2.8
3 O atoms
4 O atoms
Oxyanions (cont) 2.8
– C. add H+ to oxyanion: add hydrogen to anion name
Common Anions 2.8
Ionic Compounds 2.8
• 3. Ionic Compounds: cation name + anion name– NaCl sodium chloride
– AgNO3 silver nitrate
Acids 2.8• *recognize since typically contain H as first
element in compound*• * it is similar to an ionic compound with H+
as the cation joined to some anion*• 1
2
3
Binary Molecular Compounds 2.8
• * 2-element molecular compounds* • *naming is similar to naming ionic compounds*
• RULES:– 1—element closest to metals is written first
• *exception: compound contains O + Cl, Br or I?• O written last
– Cl2O = dichlorine monoxide
– 2—both elements in same group?• Lower one named first
– 3—name of second element ends in –ide• NF3 = nitrogen trifluoride
– 4—Greek prefixes used to indicate number of atoms on each element (mono not used with first element)
• Cl2O = dichlorine monoxide
2.8
Organic Compounds 2.9• *Can contain C,H,O,N*• Alkanes: contain only H and C; simplest
class
– 1C:4other atoms
Organic Compounds (cont) 2.9
• Alkane derivatives:– replace H with functional grp
• OH=alcohol
–Isomers: same chemical
– formulas but different arrangements of atoms
• describe key experiments that led to the discovery of electrons and the nuclear model of the atom
• understand and explain Dalton’s atomic theory including Law of Multiple Proportions
• describe atomic structure• describe electrical charge and relative masses of +,
and –• be able to use chemical symbols, atomic number and
mass number to express the subatomic composition of elements and their isotopes
• be able to calculate atomic weight from atomic masses and isotope abundances
• describe the organization of elements in the periodic table, including:
• periods and groups• metals, non-metals and metalloids• group names and characteristics
Learning Goals
• explain how ions are formed and be able to use the periodic table to predict the charges of common ions
• distinguish between molecular substances and ionic substances
• distinguish between molecular and empirical formulas
• be able to write molecular, structural and ionic formulas as well as binary inorganic compounds and acids from names and vice versa
• ID organic compounds and name simple alkanes and alcohols