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Dalton’s Atomic Theory and
Atomic Basics
Ch 4: 4.1 to 4.7
Element, Compound, or Molecule?
Element- grab your ear like so
Compound- clap as shown
Molecule-move to the groove
H2: ________
MgO: _______
Fe: _________
Na2SO4 : _______
Hg: _________
KI: __________
1. Elements are made of tiny particles
called ________
2. All atoms ____________________
3. The atoms of a given element are
_______________________________
4. Atoms of one element can combine with
_______________ to form __________.
A given compound always has the same
_______________________________
5. Atoms are not __________ or
__________ in chemical
reactions. Bonds can
_______ and _______, but
_______ cannot
2 Mg(s ) + O2(g ) --> 2 MgO(s )
Your turn 
Everyone Responds
• sulfur has 16 total electrons, while nitrogen
has only 7
• Potassium iodide (KI) combines with lead
nitrate (Pb(NO3)2) to form solid lead iodide
(PbI2)
reaction
• Hydrogen gas, H2, contains only H atoms
• The balanced chemical reaction of
magnesium with oxygen is below:
2 Mg(s ) + O2(g ) --> 2 MgO(s )
Formulas of Compounds
In a chemical formula, atoms are indicated
by element __________ and the numer of
each type of atom is indicated by a
numerical _________. The state of matter is
often indicated by _______________.
Examples:
CaCl2(s)
C6H6(l)
The modern view of the atom
Opposite charges attract, like
charges repel.
The nucleus of an atom contains:
____________________
____________________
Electron cloud contains
____________________________
The net charge of any atom or compound is
______
Masses of Particles
Proton = ________ amu
Neutron = _______ amu
Electron = _______ amu
This means that the majority of an atom’s
mass comes from _______ and _______.
Rutherford’s Experiment- 1911
• Alpha particles shot at a thin gold foil
• Some are _______, some go ________, some
__________!
– Proves atoms have positively charged nucleus
– Disproves Lord Kelvin’s __________________
Vocab time!
Atomic number:
# of _________ in the nucleus
Mass number:
sum of # of ________ + # of ___________
Find the atomic number of each of the
following: B, Au, Be, C
Practice problems
Isotopes
Atoms with the same number of ________
but different numbers of ___________
Questions:
What is the charge on an isotope?
Will the mass number of the isotope be
different than that of the more naturally
abundant atom?
Why aren’t the masses listed on the periodic tables
whole numbers?
Calculating average atomic mass:
Weighted average:
(% abund. in dec. form)*(atomic mass/weight) +….
Example #4: Silicon
mass number
exact weight
percent abundance
28
27.976927
92.23
29
28.976495
4.67
30
29.973770
3.10
The answer for silicon: 28.086
Try this one on your own!
Isotope
name
Isotope
mass
(amu)
Silver-107 106.90509
percentage
51.86
Silver-109 108.90470 remainder
The Cathode Ray Tube
J.J. Thompson discovered that atoms
contain electrons, using a CRT
diagram: