4. Bohr modelcompared electrons
to planets
• Because science is always
changing, we realized that
Bohr’s model could not
explain all of our
observations!!
5. Electrons are found in
orbitals-behave like wavesquantum theory!
There are four kinds of
orbitals:
s orbitals
p orbitals
d orbitals
f orbitals
6. Each orbital has a
different amount of
energy
Orbitals closer to the nucleus
have less energy than orbitals
further from the nucleus
7.
8.
9.
10. Valence Electrons
Electrons that are found in
the outermost energy level
of an atom
How do we know how many
valence electrons a
particular atom has???
11. The first orbital can hold
electrons
2
The second and third orbitals
can each hold 8 electrons
Higher orbitals are more
complicated and will be
learned in Chemistry class!
12. How many valence electrons
would an electrically neutral
Carbon atom have???
Carbon has 6 protons,
therefore an electrically
neutral atom would need 6
electrons to balance the
charge
13. Carbon’s first orbital can
only have 2 electrons
6 total electrons – 2
first shell electrons
leaves 4 electrons in
the outer shell (valence
shell)
16. Periodic Law says:
1) Properties of elements
tend to change according
to a regular pattern when
those elements are
arranged by increasing
atomic number!!
17. What does this mean???
It means that elements with
certain characteristics in
common (like # of valence
electrons) are more likely to
have similar chemical
properties (like what kinds
of atoms they react with!)
19. Periods and Groups
Vertical columns (up-down) are
called GROUPS
All elements in a particular
group will have the same
number of valence electrons,
which gives them all similar
chemical properties
20. Atoms that have lost or
gained electrons are
called…IONS
Atoms that have lost or
gained neutrons are
called…ISOTOPES
21. Cation=atom that has
lost electrons, giving it
a positive charge
i.e. Li +
Anion=atom that has
gained electrons,
giving it a negative
charge
i.e. Cl -
23. Metals continued
Alkali Metals-found in
Group 1
-Highly reactive
-one valence electron
-readily form cations
(+)
-not found naturally in
nature-why?
24. Alkaline Earth Metals
-Found in Group 2
-Very reactive, but not as
reactive as Alkali Metals
-2 valence electrons
-readily form cations (+2)
-too reactive to be found alone
in nature
25. TRANSITION METALS
Groups 3-12
Can form more than one
cation, depending on what
they are bonding with
Very useful in technology
and economy
26. Nonmetals
Found on the right side of the periodic
table
Very plentiful on earth-especially carbon,
silicon, oxygen, nitrogen, and sulfur
Readily form anions by gaining electrons
to form full outer shells
27. Halogens
-elements in Group 17
-very reactive, especially with alkali metals!
-7 valence electrons-only need ?? To have a full
shell…
-form anions (-1) by GAINING that one missing
electron
28. Noble Gases-Group 18
-Found in Group 18
-all inert gases
-full valence shells-do not need to get
any more electrons, therefore they
do not react with other atoms or
elements
-will not form ions
29. Semiconductors
Found on the “stairsteps”
Intermediate conductors of heat
and electricity-not as good as
metals, but better than
nonmetals
Classified as nonmetals, but have
some properties of metalssometimes called “metalloids”
30. Using Moles to Count Atoms
The mole is a counting unit, much like
“dozen” or “pair”
A dozen = 12 objects
A pair = 2 objects
A mole = 6.022 x 10 23 objects
6.022 x 10 23 is known as Avogadro's
constant
31. Molar Mass
Average atomic mass is the mass of 1
atom
Molar mass is the mass of 1 mole of
atoms
The number is the same for both of these
and can be found on the periodic table,
usually under the Chemical symbol for
that particular element
The only difference for these two values
is the unit you use -Atomic Mass Unit
vs grams/mole
32. Conversion Factors
Just as we used a conversion factor to
do our metric conversions, we will use
a conversion factor to go from
moles → mass
and
mass → moles
33. More Conversion Factors
For our purposes, the conversion factor is
the molar mass of an element-found on
the periodic table
So...
1 mole Carbon = 12.011 grams
12.011 grams Carbon = 1 mole
