Chemistry 1364
General Chemistry I
Chapter
2 - Atoms, Molecules, and Ions
Atomic Theory of Matter
n Democritus
n Greek philosopher
n First to propose finite divisions of matter
n Was not the ‘common’ belief, so fell into disfavor
n John Dalton
n English schoolteacher
n Proposed 4 postulates of atomic behavior which are the
cornerstone for atomic theory
Dalton’s Postulates
n Element - extremely small particles - atoms.
n All atoms of an element are identical; atoms of
different elements are different.
n Atoms of one type are NOT changed into atoms of
another type by chemical reactions; atoms are neither created nor destroyed in
chemical reactions.
n Compounds - formed by combining atoms of more than 1
element, and always have the same number and type of atoms.
n Elements
- 1 type of atom.
n Au,
Na, Fe, etc...
n Compound
- 2 or more types of atoms combined chemically.
n H2O,
CO2, NaClO4, etc...
n Mixture
- no interaction of atoms in elements/compounds.
n Sea
water, coffee, iced tea, etc…
n Law of conservation of mass
n Mass the same at the end as the beginning.
n Law of constant composition
n Compound will always have the same ratio of elements
n Law of multiple proportions
n 2 or more compounds from elements, then the masses of
elements will be small whole number ratios.
n Physics
- Like charges repel each other; unlike charges attract.
n Cathode
rays
n invisible,
but can cause materials to fluoresce.
n can
'bend' the rays w/magnetic or electric field.
n Amount
of bending can be used to determine the charge to mass (e/m) ratio.
n Thompson
n e/m = 1.76 x
108 coulomb / g
n If charge or mass could be determined, the other could
using the e/m ratio.
n Millikan Oil Drop Experiment
n Attempt to determine the charge on an electron.
n Charge = 1.60 x 10-19 C
n Mass = 9.10 x 10-28 g
n (1.60 x 10-19 / 9.10 x 10-28) =
1.76 x 108
n Radioactivity
n X-rays
n Not affected by magnetic fields
n Form of energy
n Becquerel - link to phosphorescence
n Rutherford
- 3 types
n a - He nucleus (2+)
n b - fast electrons
(-)
n g - similar to X-rays
n Dalton
– indivisible sphere
n Thompson
– Plum Pudding model
n Banana
nut muffin model
n Nuclear
atom
n Rutherford/Geiger/Marsden
experiment
n scattering
of a particles
n some
straight back!
n later
found protons and neutrons in the nucleus
Modern View
n Electron charge = -1.602 x 10-19 couloumb
n Proton charge = +1.602 x 10-19 couloumb
n charges equal magnitude but opposite sign
n refer relative as +1 or -1
n Nucleus very small
n 10-4 D vs atom at 1-5D
n 1 D = 10-10 m
n Masses
for atoms is extremely small
n Largest
atomic mass about 4 x 10-22 g!
n Need
an ‘atomic’ scale for masses
n Atomic
Mass Units
n amu
n Relative
to the mass of a carbon atom
n More
later…..
n Element
defined by # of protons in the nucleus
n #
protons called the atomic number (Z)
n isotopes
- different # of neutrons
n protons
+ neutrons = mass number (A)
n indicate
specific isotope by mass # and symbol - 12C, 16O, etc.
n nuclide
- atom of a specific isotope.
Problems 1, 3, 5, 11-17 odd
Periodic Table
n Triads
n early
grouping of elements based on similar chemical and physical properties
n Elements
arranged
n increasing
atomic number
n grouped
w/similar properties in columns
n Defines
'shape' of periodic table
n More
later….
n Column
- Family or group.
n IA
- alkali metals
n IIA
- alkaline earth metals
n VIA
- chalcogens
n VIIA
- halogens
n VIIIA
- noble gases
n North
American labeling convention
Molecules and Ions
n Molecules
n Distinct
packages of atoms bound together (covalent bonds)
n can
be same element or different elements (O2, HCl,C12H22O11,...)
n Diatomic
elements
n must
be neutral (no charge)
n nonmetal/nonmetal
n Formulas
n molecular - what and how much
n empirical - what in smallest whole number ratio
n structural - what is hooked to what
n Ions - charged particles
n cations (+) and anions (-)
n show charge by superscript following symbol (Na+,
Al3+, S2-, Cl-, ...)
Types of Ions
n monatomic - single atom gains/loses electrons
n use periodic table to predict charge on monatomic ion.
n polyatomic - groups of atoms (similar to molecules)
w/charge.
n Typically nonmetals with other metals
n some polyatomic ions will consist of metals/nonmetals
(CrO42-) of only metals (Hg22+)
Ionic compounds
n held together by difference in charges
n metal/nonmetal
n no molecules - use empirical formulas.
n Write formula by insuring the same number of + and -
charges.
Problems 19, 21, 25, 29-37 odd
Nomenclature
n cations
n element + ion
(Na+ - sodium ion) for A and Group 2B metallic ions
(representative)
n element + (charge in roman numerals) + ion for
variable charge
n Transition elements and heavier representatives
n Fe2+ - iron(II) ion
n Fe3+ - iron(III) ion
n Table 2-4 lists the common cations
n
Learn BOTH formula
and charge!
n anions
n drop end and replace with -ide
n chlorine 6 chloride
n sulfur 6 sulfide ...
n polyatomic (oxy) anions
n when two are formed, the one with more oxygens -ate;
fewer -ite
n NO3- - nitrate; NO2-
- nitrite
n more than 2 - use prefix per- (more, -ate) and hypo-
(less, -ite)
n look at the chlorine series
n anions
n polyatomic
oxy anions with hydrogen
n use
hydrogen or bi-
n CO32-
- carbonate; HCO3- - hydrogen carbonate or bicarbonate
n Table
2.5
n
Learn BOTH formula and charge!
n Compound
- name of cation with name of anion
n NaCl
- sodium chloride
n CaCO3
- calcium carbonate
n FeSO4
- iron (II) sulfate
n Acids
n binary
- hydrostemic acid
n HCl -
hydrochloric acid
n H2S
- hydrosulfic acid
n oxo-
n -ate 6 -ic
n -ite 6 ous
n
ClO4- - perchlorate; HClO4
- perchloric acid
n Binary molecular compounds
n use prefixes to indicate # of each type of atom
n Table 2.6
n
last element ending
changed to -ide
n CO2 - carbon dioxide
n N2O5 - dinitrogen, pentoxide
n Common names
n H2O - water; NH3 - ammonia
n others…
Problems 39 - 49 odd