Download Chapter 2 Atoms, Molecules and Ions Atomos “uncuttable” Protons +

Chapter 2 Atoms, Molecules and Ions
Atomos  “uncuttable”
Dalton’s Atomic Theory ~1805 (page 38)
…Atoms are small, indivisible balls.
Mid-1800s: scientists find that
atoms consist of:
Protons
charge
+1
Neutrons
0
Electrons
-1
Modern View of Atomic Structure
1. Atoms in their elemental form are
electrically Neutral
2. Mass of 1 proton ≈ Mass of 1 neutron
3. e- s are MUCH lighter than protons & neutrons
4. Nucleus consists of protons and neutrons only;
nuclei contain all of the positive charge and
almost all of the mass of the atom
5. Most of an atom’s volume is empty space
http://www.youtube.com/watch?v=5pZj0u_XMbc
How big are atoms?
1Å = 10-10 m
Atoms:
Atomic Number
Mass Number
Atomic Symbols
Isotopes:
Atoms of a given element that differ only in the # of
neutrons.
Atomic Weight of an Element =
Weighted average of all isotopes of the element
AW = Σ (mass of each isotope) x (its % abundance)
The Periodic Table
• Elements are arranged by atomic number, and in
groups with similar properties in vertical columns.
Group names you must know:
1 - alkali metals
2 - alkaline earth metals
3 -12 Transition metals
17 - halogens
18 - noble gases
(rare, or “inert” gases)
Location of Metals and Nonmetals
Ions
Ions have UNEQUAL #s of protons and electrons
∴ ions are charged particles
Ions form when a neutral atom loses or gains
one or more electrons.
• Metals form Positive ions
• Nonmetals form Negative ions
Metal Atoms lose e-s
(oxidation) to form
CATIONS
Non-Metal Atoms gain
e-s (reduction) to form
ANIONS
Cl
Na
Na+
e-
Cl-
When a nonmetal gains an e-, where does it come from?
Predicting Ionic Charges; can we?
sometimes….
how?
• Find nearest noble gas
• Use periodic table; count # of e-s a metal
must lose or a nonmetal must gain
• Note: Cannot predict for ALL atoms, but
can often tell from formula.
Ions combine to form Ionic Compounds, which are
1.  Composed of ions ;
with
2. Neutral overall; Amount of
positive charge must equal
amount of negative charge.
3. Formed by transfer of
e-(s) from metal to nonmetal
4.  Held together by electrostatic attraction
Pg. 60 & 62
Group 1A
Group 2A
Group 3A
Group 7A
Group 6A
Group 5A
Can’t predict!
Nomenclature =naming substances.
1.Ionic Compounds
Cation name is unchanged
Add anion name: Simple anions - names end in ide
• if cation’s (metal’s) charge is variable use Roman numerals
PbS
HgS
vs PbS2
vs Hg2S
Fe2O3
vs FeO
2. Polyatomic Ions; many common ones
end in –ide or -ate
ex.
OH- (hydroxide ion)
CN- (cyanide ion)
C2H3O2- (acetate ion)
• Polyatomic cations have -ium ending
Oxyanions
Memorize these 5 common oxyanions:
NO3-
nitrate
ClO3- chlorate
CO32- carbonate
SO42- sulfate
PO43- phosphate
All related forms are derived from these
Green = Ba(NO3)2
Red = SrCO3,
Li2CO3
Stars = KClO4
Black = PbO2
White= PbCO3
Blue
= CuSO4
Reddish-yellow =PbO
Green =FeSO4
Oxyanions
Common form = ate
ex: SO42- (sulfate ion)
• one less O = ite
ex: SO32- (sulfite ion)
• One more or two fewer O s; Use Prefixes :
perchlorate ion (ClO4-)
chlorate ion
(ClO3-)
chlorite ion
(ClO2-)
hypochlorite ion (ClO-)
Announcements
1. Office hours canceled today; Chapter 2 homework
is now due Monday night instead of Sunday night…
2. If you are in lab section:
036
Monday 2- 5 pm
TA: Awanthi
037/S37 Tuesday 1-4 pm
TA: Lyndsay
or
You will take the exam upstairs in SEM 326
next Friday.
Figure 2.26 (p. 61)
Note:
• Oxyanions with 2- and 3- charges can add H+
to form anions with less negative charge.
Acids
Neutral compounds that produce H+ ions in water
• Acids formed by simple anions have a hydro
prefix and an ic suffix:
• ex. HCl is hydrochloric acid.
HF is ?
• Anions whose names end in ate have acids with
an ic suffix:
• HNO3 is nitric acid.
• H2SO4 is sulfuric acid
• HSO4- is NOT named as an acid; why not?
Molecular Compounds
1. Made of neutral nonmetal atoms only
2. Neutral overall; no charges involved (no ions!)
3. Formed by sharing of e-s between atoms
• Chemical formulas
• Empirical formulas
Homonuclear Diatomic Molecules:
7 exist in nature
Binary Molecular Cmpds:
• Contain two different nonmetals
• Named like ionic compounds, except
• Prefixes are used to indicate how
many atoms of each element:
• mono (1)
• di (2)
• tri (3)
• tetra (4)
• penta (5)
• hexa (6)
• hepta (7)
• octa (8)
NaCl
SiO2
(table salt)
sand
CaCO3
limestone,
shells
quartz