Transcript 04-Atoms_ molecules _ ions

Chapter 2
Atoms,
Molecules &
Ions
Atomic Theory
• Elements composed of atoms
• Atoms can’t be changed by
“normal” chemical reactions
• Compounds of multiple atoms
• John Dalton
Conservation of Mass
•In ordinary chemical
reactions, matter can
be neither created nor
destroyed
Constant
Composition
•Compounds contain
elements that are always
in the same proportions
Period 2 stopped here 9/7/06
Multiple Proportions
•The elements
making up a
compound will form
whole number ratios
Atom
•The smallest particle an
element can be broken
down into and still
maintain the identity of
the element
Nuclear Atom
•Proved by
Rutherford & Bohr
in the famous gold
foil experiments
Subatomic Composition
•Proton: in the nucleus
•Neutron: in the nucleus
•Electron: outside the
nucleus
Proton
•In Nucleus
•+1 relative charge
•About 1 amu in mass
Neutron
•In nucleus
•Neutral, zero charge
•Mass is about 1 amu
Electron
•Outside the nucleus
•-1 in relative charge
•Negligible mass
about 1/2000 amu
Electron Charge
•Determined by
Robert Milliken in
the famous oil
droplet experiment
Atomic Number
•The number of
protons in an
element
•Z number
Mass Number
= number of protons
and neutrons in an
atom
A - number
Nuclear Symbol
A
4
X
Z
General
Formula
He
2
Specific
Example
Isotopes
•Atoms that contain the
same number of protons,
but different number of
neutrons
•Z constant, A variable
Isotopes are useful!
• C14- dating
• Isotopic - tracing – Works
like a flag – you can follow
an atom or molecule
through a reaction
Shorthand for isotopes
Instead of
full notation:
14
C
Write: C-14
6
So, only the A number
(protons + neutrons)
Atomic Mass
• All elements have >1 isotope.
• The percentage of one isotope is its
relative abundance.
• Atomic mass =
(A # of isotope 1 x % isotope #1) +
(A # of isotope 2 x % isotope # 2) + etc…
Periodic Table
• Hierarchy of all the elements.
• The order is used to predict
size, charge, electronic
structure & reactivity of
elements
Periods
•Rows which
indicate energy
level or shell or
size of the atoms
Groups or Families
•Columns which indicate
the number of electrons
in the outermost energy
level determining
charge & reactivity
Metals
•Left three quarters of
the chart
•Lose electrons
•Become positive
Nonmetals
•Upper right portion
•Gain, lose, or share
electrons when they
react
Metalloids
•Along the stair-stepped
line from B to At
•Share properties of
metals & nonmetals
Radioactivity
•The spontaneous
breakdown of an
unstable nucleus
Compound
•A grouping of atoms
that are chemically
combined
Molecule
•A compound
that can exist
by itself
Diatomic Molecule
•Two atoms of the same
element that are
chemically combined
•Cl2, F2, O2
Ion
•Charged Particle
-1
•Cl
Polyatomic Ion
•A group of atoms
chemically combined
that together has a charge
-2
•SO4
9/7/06 period 1 stopped here
Binary Compound
•A compound made up of
two elements in any ratio
•NaCl
•Mg3P2
Chemical Formula
•A formula that shows the
number and kinds of
atoms in a compound
•CaCO3
Molecular Formula
•A formula that shows
the number and kinds
of atoms in a molecule
•C6H12O6
Period 4 stopped here 9/7/06
Atomic Structure
•List & describe the
three subatomic
particles
Atomic Structure
•Fill in the Chart:
• Isotope protons neutrons electrons
• U-235
• 56
80
• 14
13
Calculate the atomic mass of
the element made up of the
following isotopes:
99.50 % H-1
0.30 % H-2
0.20 % H-3
Calculate Pt’s atomic mass :
5.0 % Pu-242
5.0 % Pu-243
80.0 % Pu-244
10.0 % Pu-245
Determine the number
of atoms in each
compound
•C6H12O6 NaNO3
•H3PO4 Al2(SO4)3