General Chemistry I
2 - Atoms, Molecules, and Ions
Atomic Theory of Matter
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
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
n Compounds - formed by combining atoms of more than 1
element, and always have the same number and type of atoms.
- 1 type of atom.
Na, Fe, etc...
- 2 or more types of atoms combined chemically.
CO2, NaClO4, etc...
- no interaction of atoms in elements/compounds.
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.
- Like charges repel each other; unlike charges attract.
but can cause materials to fluoresce.
'bend' the rays w/magnetic or electric field.
of bending can be used to determine the charge to mass (e/m) ratio.
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 Not affected by magnetic fields
n Form of energy
n Becquerel - link to phosphorescence
- 3 types
n a - He nucleus (2+)
n b - fast electrons
n g - similar to X-rays
– indivisible sphere
– Plum Pudding model
nut muffin model
of a particles
found protons and neutrons in the nucleus
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
for atoms is extremely small
atomic mass about 4 x 10-22 g!
an ‘atomic’ scale for masses
to the mass of a carbon atom
defined by # of protons in the nucleus
protons called the atomic number (Z)
- different # of neutrons
+ neutrons = mass number (A)
specific isotope by mass # and symbol - 12C, 16O, etc.
- atom of a specific isotope.
Problems 1, 3, 5, 11-17 odd
grouping of elements based on similar chemical and physical properties
w/similar properties in columns
'shape' of periodic table
- Family or group.
- alkali metals
- alkaline earth metals
- noble gases
American labeling convention
Molecules and Ions
packages of atoms bound together (covalent bonds)
be same element or different elements (O2, HCl,C12H22O11,...)
be neutral (no charge)
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)
n Typically nonmetals with other metals
n some polyatomic ions will consist of metals/nonmetals
(CrO42-) of only metals (Hg22+)
n held together by difference in charges
n no molecules - use empirical formulas.
n Write formula by insuring the same number of + and -
Problems 19, 21, 25, 29-37 odd
n element + ion
(Na+ - sodium ion) for A and Group 2B metallic ions
n element + (charge in roman numerals) + ion for
n Transition elements and heavier representatives
n Fe2+ - iron(II) ion
n Fe3+ - iron(III) ion
n Table 2-4 lists the common cations
Learn BOTH formula
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;
n NO3- - nitrate; NO2-
n more than 2 - use prefix per- (more, -ate) and hypo-
n look at the chlorine series
oxy anions with hydrogen
hydrogen or bi-
- carbonate; HCO3- - hydrogen carbonate or bicarbonate
Learn BOTH formula and charge!
- name of cation with name of anion
- sodium chloride
- calcium carbonate
- iron (II) sulfate
- hydrostemic acid
n HCl -
- hydrosulfic acid
n -ate 6 -ic
n -ite 6 ous
ClO4- - perchlorate; HClO4
- perchloric acid
n Binary molecular compounds
n use prefixes to indicate # of each type of atom
n Table 2.6
last element ending
changed to -ide
n CO2 - carbon dioxide
n N2O5 - dinitrogen, pentoxide
n Common names
n H2O - water; NH3 - ammonia
Problems 39 - 49 odd