Download Ch 2 Notes

Atoms, Molecules, and Ions
Old Dead Greek Guys (400 B.C.)
 Democritus— matter is made up of
indivisible particles
 Aristotle—matter is continuous
2.1
Antoine Lavoisier (1789)
 The Father of Modern Chemistry
 Law of Conservation of Mass
 Mass is neither created nor destroyed
 Discovered 33 elements
2.2
M. & Mme. Lavoisier
2.2
Joseph Louis Proust (1800ish)
 Law of Definite Proportion
 A given cmpd always contains exactly the
same proportion of elements by mass
2.2
Dalton’s Atomic Theory (1808)
1. Each element is made up of tiny particles
called atoms
2. The atoms of a given element are identical,
that atoms of different elements are different
3. Cmpds are formed when atoms of diff.
elements combine, a given cmpd has same #
& types of atoms
4. Rxns involve reorganization of atoms
2.3
John Dalton
2.3
Dalton’s Model of the Atom
 Called the Marble Model
2.3
J. J. Thomson
2.4
J. J. Thomson (1898-1903)
 Studied cathode ray tubes
 “ray” was a stream of negatively charged
particles, called electrons
 He get credit for discovering electrons
2.4
Cathode Ray Tube (CRT)
Direction of electron travel
Cathode:
- electrode
Anode:
+ electrode
2.4
J. J. Thomson
 Used the CRT to measure the charge to mass ratio of
an electron
 e/m = -1.76 x 108 C/g
 e = charge on e- in coulombs (C)
 m = e-’s mass in grams (g)
2.4
Plum Pudding Model
2.4
Millikan’s Oil Drop (1909)
 Did an experiment with charged oil drops
 Used e/m & the magnitude of the e- charge to
calc the mass of an e Mass of e- = 9.11 x 10-31 kg
2.4
Millikan’s Oil Drop
2.4
Radioactivity
 Henri Becquerel Accidentally Discovered
Radioactivity
 Marie and Pierre Curie Studied radioactivity
and discovered other radioactive elements.
2.4
Becquerel (1896)
 Discovered radioactivity by accidentally placing a
uranium “rock”
onto a photographic plate
2.4
Radioactivity
 Spontaneous emission of radiation from an
element
 a radiation: attracted to neg. plate

Particles w/ 2+ charge
 b radiation: attracted to pos. plate

High-speed electrons
 g radiation: no attraction

Not particles, similar to X-rays
2.4
a
g
b
Earnest Rutherford
 Gold foil experiment, also called the a-particle
experiment
 Discovered the nucleus: center has a positive charge
and most of the atoms mass
 Electron move around the nucleus at a distance that is
large relative to the nuclear radius
a-particle experiment
 a-particles were shot at a sheet of gold foil
 Most particles went straight through representing that
atoms are mostly empty space
 Some particles were deflected off of the gold foil
showing that there was in fact a dense nucleus in the
center of an atom
Rutherford Model
Niels Bohr
Bohr Model
 The e-’s orbit the nucleus of an atom in specific
pathways
 Also called the solar system model since it
mimics how the planets orbit the sun
Bohr Model
Structure of the Atom
Particle
Symbol
Charge
Mass (amu)
Location
Proton
p
Positive
1
Inside
Neutron
n
Neutral
1
Inside
Electron
e-
negative
0
Outside
Atomic Number
 The # of protons in an atom
 Also gives the # of e-’s since an atom is
electrically neutral
 For every proton there is an e What makes one element different from
another
50
Sn
Tin
Ion
 When an atom gains or loses one or
more e-’s
 Gain of e-  neg. charge
 Loss of e-  pos. charge
Ion Problems
1. How many protons, neutrons, and
25
2
electrons are present in the 12
Mg ion?
2. Write a chemical symbol for the ion with
74 p and 68 e-.
Ion Problems - Answers
1. How many protons, neutrons, and
25
2
electrons are present in the 12
Mg ion?
 12 p, 13 n, 10 e2. Write a chemical symbol for the ion with
74 p, 110 n, and 68 e-.

184
74
W
6
.
Mass Number
 The number of protons + neutrons
 Protons and neutrons are called nucleons
Isotopes
 Atoms that have the same # of protons but a
different number of neutrons
 Major diff between two isotopes is their mass
 Example:
 Carbon-12: 6 protons, 6 neutrons, 6 electrons
 Carbon-14: 6 protons, 8 neutrons, 6 electrons
Chemical Symbol
Mass # (M)
141
56
Ba
Atomic #
(Z)
2
Charge
Chemical Symbols
# of protons = Z
# of neutrons = M – Z
# of electrons = Z – charge
Problems
1. How many p, n, &
e
are
present in the 59 Ni2 ion?
28
 Write the chemical symbol
for the ion with 53 p, 74 n,
and 54 e-.
Problems - Answers
1. How many p, n, & e- are
2  ion?
present in the59
28 Ni
 28 p, 31 n, & 26 e-
2. Write the chemical symbol
for the ion with 53 p, 74 n,
and 54 e-.
 Symbol =
127 
53
I
Atomic Mass
 Atomic mass is the average mass of all the
isotopes of the element
 Weighted by abundances of isotopes
 Based on Carbon-12 isotope: def’n of atomic
mass unit
READ IT!!!!
READ IT!!!!
Naming Ionic Compounds
 Use your common ion chart
 The common ions must be
memorized! You will NOT get to use
the chart on any test.
Monatomic Cations
Same name as the element
Group IA  +1 ions
Group IIA  +2 ions
+
Na
= soduim
Monatomic Cations
 Transition metals will form more than one cation
 Add roman numerals to name for the charge
 Fe2+  iron(II)
 Fe3+  iron(III)
Monatomic Anions
 Name ends in –ide
 Cl- = Chlorine  Chloride
 Group VIIA  -1 ions
 Group VIA  -2 ions
Polyatomic Ions
 Get their names from the common ion chart
 SO42- = sulfate
 PO43- = phosphate
Sample Problems
 What are the formulas for
1. sodium bromide
2. copper(II) phosphate
Sample Problems - Answers
 What are the formulas for
1. sodium bromide

Na+ Br-  NaBr
2. copper(II) phosphate

Cu2+ PO43-  Cu3(PO4)2
Sample Problems
 What are the names for
1. NaC2H3O2
2. Fe(OH)2
Sample Problems - Answers
 What are the names for
1. NaC2H3O2

Na+ C2H3O2-  sodium acetate
2. Fe(OH)2

Fe2+ OH-  Iron(II) hydroxide
Oxyanions
 Series of anions with varying #’s of oxygen
atoms
 Smaller # of O’s: -ite
 Larger # of O’s: -ate

Ex: SO32- sulfite
SO42- sulfate
More than 2 oxyanions:
 ClO ClO2-
 ClO3 ClO4-
hypochlorite
chlorite
chlorate
perchlorate
Sample Problems
 What are the formulas for
1. cesium perchlorate
2. sodium hydrogen carbonate
Sample Problems - Answers
 What are the formulas for
1. cesium perchlorate

Cs+ ClO4-  CsClO4
2. sodium hydrogen carbonate

Na+ HCO3-  NaHCO3
Sample Problems
 What are the names for
1. Fe(NO3)3
2. KH2PO4
Sample Problems - Answers
 What are the names for
1. Fe(NO3)3

Fe3+ NO3-  iron(III) nitrate
2. KH2PO4

K+ H2PO4-  potassium hydrogen
phosphate
Naming Covalent Cmpds
 Numerical prefixes are used
 Common ion chart is not used
Numerical Prefixes
1. mono2. di3. tri4. tetra5. penta-
6. hexa7. hepta8. octa9. nona10. deca-
Naming Covalent Cmpds
 If there is only one atom of the first
element it doesn’t get a prefix
Naming Covalent Cmpds
 Element furthest to the right in
periodic table (or the most
electronegative element) is named 2nd
and its name ends in -ide
Sample Problems
 What are the formulas for
1.
boron trifluoride
2. diphosphorous pentoxide
Sample Problems - Answers
 What are the formulas for
boron trifluoride
1.

BF3
2. diphosphorous pentoxide

P2O5
Sample Problems
 What are the names for
1. SiO2
2. CO
Sample Problems - Answers
 What are the names for
1. SiO2

Silicon dioxide
2. CO

Carbon monoxide
Acids
 Give off protons (H+) in water
 Acids ionize into H+ ions and an anion A HA  H+ + A HCl  H+ + Cl-
Acids w/o oxygens
 Prefix: hydro Suffix: –ic acid
 HCl: hydrochloric acid
 H2S: hydrosulfuric acid
Acids w/ Oxygen in Anion
-ate to –ic acid
2. -ite to –ous acid
1.
Acid
Anion Name
Acid Name
H2SO4
SO42Sulfate
SO32Sulfite
Sulfuric acid
H2SO3
Sulfurous acid
Oxyacids
Acid
Anion
Name
HClO
Hypochlorite
Hypochlorous acid
HClO2
Chlorite
Chlorous acid
HClO3
Chlorate
Chloric acid
HClO4
Perchlorate
Perchloric acid