John Dalton’s Atomic Theory
1. Matter is composed of atoms. Atoms are composed of
protons, neutrons and electrons
2. All atoms of the same element are identical
3. Atoms of different elements are different
4. During a chemical reaction,
atoms combine to form new
products
John Dalton’s Atomic Theory
Each element has a different size because:
# of atoms
# of electrons
Therefore: the higher the atomic number, the bigger the
atom of the element will be.
H
O
H
Organization of Matter
Elements – building blocks of the universe
*made up of atoms
Atoms – smallest unit of matter
*made up of protons, neutrons and electrons
Protons and Neutrons make up the NUCLEUS of the atom
Electrons are located on SHELLS orbiting the nucleus
* also called orbitals
Organization of Matter
Molecules – combination of 2 or more atoms
*made up of same OR different atoms (eg. CO2 or O2)
Compound – molecule of different atoms
*H2O, CO2…
Chemical Formula – shows us how many of each atom in a
molecule
Periodic Table
A list of elements and their properties
Arranged by
Rows called PERIODS
Columns called FAMILIES
Reading horizontally, the elements atomic numbers
increase by 1
Elements in the same family all have the same number of
electrons in their outer shells*
* later slides explain
Chemical Symbols
All elements have a chemical symbol
eg.
C = Carbon
Na = Sodium
*1st letter is CAPITALIZED, 2nd is small – VERY IMPORTANT!!!
Atomic Number.
Tells us the how many protons are in the nucleus
AND
How many electrons on the shells
Shells or Orbitals
Like the moons of a planet,
ELECTRONS orbit the atoms nucleus
Each shell has a maximum capacity
Shell #1
– 2 Electrons
Shell #2
– 8 Electrons
Shell #3
– 8 Electrons
Shell #4
– 8 Electrons
Insert copy of the periodic table.
Rows on the periodic table are called periods.
All the elements listed in a row belong to the
same period. There are 7 (seven) periods.
Columns in the periodic table are called groups
or families. All elements in a group have
similar properties.
Insert copy of the periodic table.
The columns have been given an Arabic number.
The columns are numbered 1 – 18 starting at the
left and moving to the right. Please make sure that
your periodic table has them numbered like this.
Insert picture of periodic table.
Group 1 and 2 the number of Valence
electrons in the outer energy level will
match the group number.
Insert picture of periodic table.
Groups 3 through 12 do not follow any
particular rule to determine the number
of Valence electrons.
Insert picture of periodic table.
Group 13 to 18 – The Valence electrons
for each of these is the group number
less 10. For example Group 14 – 10 = 4
Valence electrons.
Elements whose atoms
gain, lose or share
electrons are reactive and
they combine to form the
many compounds we use
in our daily lives.
Elements are categorized as
metals, nonmetals or
metalloids.
Metals: An element that has
luster, is malleable and ductile,
and is said to be a good
conductor of heat and
electricity.
What is luster, malleable and
ductile?
Luster describes the way a surface reflects
light…therefore metallic luster would be shiny
like a metal object.
Malleable means to be able to press or pound
the substance into sheets or different shapes.
Ductile means that the substance can be
drawn out into thin wires.
Elements are categorized as metals,
nonmetals or metalloids (cont’).
Nonmetals: an element that is
usually a gas or a brittle solid
at room temperature. It is a poor
conductor of heat and
electricity.
Elements are categorized as metals,
nonmetals or metalloids (cont’).
Metalloid: an element that
shares some characteristics or
properties with both metals and
nonmetals.
Group 1 and 2 Elements:
These elements are so
reactive that they are only
found combined with other
elements in nature.
3
Group 1: Alkali Metals
Li
Lithium
6.941
11
Na
Sodium
22.990
19
•Soft – can be cut with a knife
•Shiny and silver colored
•Low Density (some will even float)
K
Potassium
39.098
•Most reactive of the metals
37
Rb
Rubidium
•Valence electrons = 1
85.468
55
Cs
Cesium
•Reacts violently with water
forming a hydrogen gas
132.905
87
Fr
Francium
223.020
•Compounds from these are very
useful such as NaCl
4
Be
Beryllium
9.012
12
Mg
Magnesium
24.305
20
Group 2: Alkaline- Earth Metals
•Very reactive but not as reactive
as Alkali Metals.
•Silver colored
Ca
Calcium
40.078
38
Sr
Strontium
87.62
56
Ba
barium
137.327
88
Ra
Radium
226
•More dense than Group 1 metals
•Valence electrons = 2
•Useful compounds include: Calcium
compounds such as cement, plaster,
chalk, and YOU.
6
C
Carbon
12.011
14
Si
Silicon
28.086
Group 14: Carbon Group
•Reactivity varies in this group
depending on the element
•Valence electrons = 4
32
Ge
Germanium
72.64
•This group contains 2 metals, 1
nonmetal and 2 metalloids.
50
Sn
Tin
118.710
82
Pb
Lead
207.2
•Many forms found uncombined
in nature such as diamonds
•Compounds are very useful:
proteins, fats, carbohydrates,
computer chips.
1
H
Hydrogen
1.008
Hydrogen Stands Alone:
•Properties do not match the properties
of any single group
•Valence Electrons = 1
•Easily looses that one valence electron
•Physical properties are like the
nonmetal group
•Most abundant element in the
Universe
•Its reactive nature makes it useful as a
fuel for rockets.
Valence Electrons
The outer most energy level is
usually not full or complete .
These electrons in the outer
energy level are called Valence
electrons.
Valence electrons are important
because they determine how an
element will react with other
substance.
Valence Electrons
The outer most energy level is
usually not full or complete .
These electrons in the outer
energy level are called Valence
electrons.
Valence electrons are important
because they determine how an
element will react with other
substance.