# Chapter 3 – Atoms and the Periodic Table by dfhdhdhdhjr

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```									 Chapter 3 –
Atoms and the
Periodic Table
3.1 Atomic
Structure
Atoms
Derived from the Greek
word meaning “unable
to divide”.
They are the building
blocks of molecules.
Every element is
unique particles
that cannot be
subdivided.
Atoms of the same
element are exactly the
same.
Atoms of different
elements can join to
form molecules.
protons, neutrons,
and electrons.
Nucleus
The center of an
protons and
neutrons.
Proton
A positively charged
subatomic particle in
the nucleus of the
atom
Neutron
A neutral subatomic
particle in the
nucleus of an atom.
Electron
A tiny negatively
charged subatomic
particle moving
around outside of an
atom.
Atoms have no overall
charge.
Even though atoms have
charged protons and
electrons. They have an
equal number of each. So,
they cancel each other out.
Bohr’s Model
In 1913, Neils Bohr suggested
The path defines
the electron’s
energy level.
Energy Level
Any of the possible
energies of an
electron may have
in an atom.
Modern theory states
that electrons behave
more like waves.
In 1925, Bohr proposed a
new model, that the
electrons do not follow a set
path.
Although we cannot know how the
electron travels around the nucleus
we can know where it spends the
majority of its time (thus, we can know
position but not trajectory).
The “probability” of finding an electron
around a nucleus can be calculated.
Relative probability is indicated by a
series of dots, indicating the “electron
cloud”.
Electrons are
found in
orbitals within
energy levels.
Orbital
A region in an atom
where there is a
high probability of
finding electrons.
Electrons may
occupy four
different
orbitals.
s - orbital
- Simplest orbital.
- Can only have one
orientation in space,
because its shaped like a
sphere.
- Its shape enables it to surround the
nucleus.
- 90% electron probability/cloud
for 1s orbital (notice higher
probability toward the center)
- It can hold a maximum of 2
electrons.
p - orbital
-it is a dumbbell-
shaped and can be
oriented in 3
different ways in
space. (3-Dimensions)
d - orbital
-a more complex
orbital.
-There are a possible
of 5 orientations.
-All orbitals are very
different in shape, each
can contain a maximum
2 electrons.
-Can contains a total of
10 electrons in all.
Four of the d orbital’s
resemble two
dumbbells in a clover
shape. The last d
orbital resembles a p
orbital with a donut
wrapped around the
middle.
f - orbital
-a more complex
orbital.
-There are a possible
of 7 orbitals.
-All orbitals are very
different in shape, each
can contain a
maximum 2 electrons.
-Can contains a total of
14 electrons in all.
Electrons usually
occupy the lowest
energy levels
available.
And within each
energy level,
electrons occupy
orbitals with the
lowest energy.
An s orbital has the lowest
energy.
A p orbital has slightly
more energy, followed by
a d orbital.
An f orbital has the
greatest energy.
Every atom has
one or more
valence electron.
Valence Electron
An electron in the
outermost energy
level of an atom.
3.2 A Guided
Tour of the
Periodic Table.
Periodic Law
Properties of elements tend
to change in a regular
pattern when elements are
arranged in order of
increasing atomic number,
or number of protons in
their atoms.
Period
A horizontal row
elements in the
periodic table.
As you move across a
row the # of protons
increases by 1. As does
the # of electrons.
Elements in the
same group
have similar
properties.
Group
(family) – a vertical
column of
elements in the
periodic table
Elements in the
same group have
the same # of
valence
electrons.
These elements are
not exactly alike,
they have a different
# of protons and
electrons.
Some atoms
form ions
Some atoms may
under go
ionization.
Ionization
electrons to or removing
electrons from an atom
or groups of atoms.
These are valence
electrons.
Ions
An atom or a group of
atoms that has lost or
gained 1 or more
electrons and therefore
has a net charge.
Cation
An ion with a
positive charge
Example: Lithium atom
Lithium is so reactive, it
reacts with air. It has 1
electron in the outer level
of the s orbital. This one
electron makes very
reactive.
Removing this electron
forms a positive ion
(Li +)

Li + is less reactive,

because now its outer
energy level is full.
Anion
An ion with a
negative charge.
Example: Fluorine atom
Fluorine is also very
reactive; however it
gains an electron to
become less reactive.
It has 7 valence electrons
and needs only 1 to
complete its outer energy
level.
Therefore, easily gaining 1
electron & becoming a
negative ion (F -).
Atomic Structure of
Atoms
All atoms have different
structure and different
properties; therefore,
different structure.
Atomic Number
(Z)
The number of
protons in the
nucleus of an atom.
Examples:
Helium (He) has 2
protons
Z=2
Cesium (Cs) has 55
protons
Z = 55
Mass Number (A)
Mass number equals
the # of protons and
neutrons in the
nucleus in the atom.
Ex: Fluorine (F)
has 9 protons and
10 neutrons, A =
19 for fluorine.
Although atoms of the
same element always
have the same
Atomic number, they
can have a different
mass numbers.
Isotopes
Any atoms have the
same # of protons,
but a different # of
neutrons.
Ex: Hydrogen has 3
isotopes.
1. Protium – has 1
proton in its nucleus.
(A = 1) Most common
form
2. Deuterium – has 1
proton and 1 neutron
in its nucleus, call
heavy hydrogen.
(A = 2)
3. Tritium – has 1
proton and 2
neutrons in its
nucleus. (A = 3)
Atomic numbers (Z)
and mass numbers (A)
maybe included with
the chemical symbol.
A
ZX
Mass Number
235
92   U
Atomic Number
Calculating the # of
neutrons in an atom.
If you know the Atomic
number and the Mass
number, all you have
to do is subtract.
# of Neutrons
=
mass # – atomic #

(# of Neutrons = A – Z )
Ex: For our
Uranium - 235
# of Neutrons = A – Z
# of Neutrons = 235 – 92
# of Neutrons = 143
The mass of an atom.
The mass of a single atom
is very small. A single
Fluorine atom is one
trillionth of one billionth
of a gram.
Because it is very hard
to work with atomic
mass are expressed in
atomic mass units
(amu).
atomic mass unit
(amu)
A quantity equal to
1/12 of the mass of
a Carbon-12 atom.
average atomic
mass
The weighted average
of the masses of all
naturally occurring
isotopes of an element.
EX: If we look back at
Hydrogen.
There are 3 isotopes. The
average atomic mass 1.00794
amu. This means there are
more isotopes of Hydrogen-1,
than Hydrogen-2 or Hydrogen-
3.
3.3 Families of
Elements
Elements are either
classified as Metals
or Nonmetals.
Metals
The elements that are
good conductors for
heat and electricity.
Most elements
are metals.
Usually solids
and shiny.
Nonmetals
The elements that
are usually poor
conductors of heat
and electricity.
Nonmetals, except
Hydrogen, are found on
the right side of the
periodic table.
Can be solids, liquids, or
gases.
Solids are dull and brittle.
There are some
nonmetals that can
conduct under
certain
circumstances.
Semiconductors
The intermediate
conductors of heat and
electricity.
Sometimes called
metalloids.
Metals can be
classified even
further into 4
different groups.
Alkali Metals
Highly reactive
metallic elements
located in Group 1
of the periodic table.
•Has 1 valence
electron.
•Can be easily
removed to form a +1
ion.
•Highly reactive.
Look on your
Periodic table.
Lithium Sodium
Potassium Rubidium
Cesium    Francium
Since they are so reactive,
these elements are not
found in nature. They
combine with other
elements to form
compounds.
Alkaline Earth
Metals
The reactive metallic
elements located in
Group 2 of the
Periodic Table.
•They have 2 valence
electrons.
•They are less reactive
than alkali metals.
•May form an ion of a +2
charge if both valence
electrons are removed.
Look at the
Periodic Table
•Beryllium Magnesium
•Calcium    Strontium
They are combine with
other elements to form
compounds.
Ex: Calcium Compounds
– shells of sea life, coral
reefs, limestone, or
marble.
Magnesium
Compounds –
speeds up the
processes of the
human body.
Transition Metals
The metallic
elements located in
groups 3 – 12 of the
periodic table.
•Much less reactive than
Alkali or Alkaline
Metals.
•Can lose electrons to
form + ions.
•Some metals can lose up
to 4 electrons.
All Metals are good
heat and electrical
conductors.
They can be stretched and
shaped without breaking.
Mercury is the only
metal that is a
liquid at room
temperature.
Technetium and
Promethium are
synthetic
elements.
•Technetium is used to
help diagnose cancer
and other medical
problems.
•Promethium is used in
‘glow in the dark’ paint.
•Elements with atomic #
greater than 92 are man
Nonmetals
•Found on the right side
of the periodic table.
•Some elements in
groups13-16 and all in
groups 17 & 18.
•May gain
electrons to form
– ions
•Carbon combines with
other elements to form
millions of carbon
containing compounds.
•Carbon compounds are
found in both living and
nonliving things.
Nonmetals and
there compounds
are plentiful on
Earth.
Halogens
The highly reactive
elements located
in Group 17 of the
periodic table.
•The valence shell is
almost full; therefore,
these elements easily
accept an electron.
•Creating a (-) ion,
anion.
•Fluorine
•Chlorine
•Bromine
•Iodine
•Astatine
Noble Gases
•The unreactive
gases located in
Group 18 of the
Periodic Table.
•These elements exist
only as single atoms,
•All gases are inert,
non-reactive.
•Outer level is full of
electrons.
•They don’t form with
other elemental
atoms to form atoms.
Helium Neon
Argon Krypton
Semiconductors
•Elements classified as
nonmetals, each one
has some properties of
metals.
•Known as ‘metalloids’
•They are able to conduct
heat & electricity.
•Silicon most familiar,
used for computers and
other electronic devices.
•Boron     Silicon
•Germanium
•Arsenic
•Antimony
•Tellurium
3.4 Using
Moles to
Count Atoms.
Counting Things
•One of the first things
we do as child.
•When we count large
#’s of small things, we
use counting units.
The mole is useful
for counting small
particles.
Mole
The SI base unit that
describes the amount
of a substance.
A mole is a collection
of a very large
number of particles.
602,213,670,000,
000,000,000,000
Constant
•The # of particles in
1 mol; equals 6.022
x 1023 /mol.
Molar Mass
The mass in
grams of 1 mol
of a substance.
Ex: 1 mole of
Titanium-22 atoms
has a molar mass of
47.87 g
•Think of it as
47.87 grams per
mole of Titanium.
•47.87 g/mol
Molar mass of an
element in grams
is the same as
average atomic
mass in amu.
Find the molar mass for
the following elements:
1.Gold
2.Einsteinium
3.Gallium
4.Cesium
Find the molar mass for
the following elements:
1.Gold        196.97 g
2.Einsteinium 252.08 g
3.Gallium      69.72 g
4.Cesium      132.91 g
Conversion Factors
A ratio equal to one
that expresses the
same quantity in
two ways.
Can be anything:
1 ream of = 500 sheets
paper      of paper
1 inch = 2.54 cm
10 km = 6.2 miles
Converting
Amount (mol) to
Mass (g)
•1st establish the amount
of matter in moles from
the problem.
•2 nd look up the element

of the period table and
find its molar mass in g
for conversion factor
Conversion factor will
be:
Atomic mass(g)=1 mole
or
1 mole=Atomic mass(g)
Set up for factor
label method.
Given
info
Set up for factor
label method.
Given   atomic mass of
info      element
Set up for factor
label method.
Given    atomic mass of
info       element
1mole of element
Ex: How many grams
in 23 moles of Silver?
23 mol
of Ag
Conversion Factor
1 mol of Ag
=
107.8682 g of Ag
Ex: How many grams
in 23 moles of Silver?
23 mol 107.8682 g
of Ag   of Ag
Ex: How many grams
in 23 moles of Silver?
23 mol 107.8682 g
of Ag   of Ag
1 mol of Ag
2480.96 g of Ag
- Multiply #’s above the
horizontal line
- Units of moles of Ag
will cancel leaving just
grams of Ag.
Ex: How many grams
2.8 mol
of Rn
Conversion Factor
1 mol of Rn
=
222.0176 g of Rn
Ex: How many grams
2.8 mol 222.0176 g
of Rn   of Rn
Ex: How many grams
2.8 mol 222.0176 g
of Rn    of Rn
1 mol of Rn
621.64928 g of Rn
Converting Mass (g)
to Amount (mol)
Set up is the same
except we switch/flip
the conversion factor
ratio.
Ex: Convert 729 g of
Th to moles.
729 g
of Th
Conversion Factor
1 mol of Th
=
232.0381 g of Th
Ex: Convert 729 g of
Th to moles.
729 g    1 mol of Th
of Th
Ex: Convert 729 g of
Th to moles.
729 g    1 mol of Th
of Th
232.0381 g of
Th
3.142 mol of Th
Ex: Convert 50 g of Sr
to moles.
50 g
of Sr
Conversion Factor
1 mole of Sr
=
87.62 g of Sr
Ex: Convert 50 g of Sr
to moles.
50 g      1 mol of Sr
of Sr
Ex: Convert 50 g of Sr
to moles.
50 g      1 mol of Sr
of Sr
87.62 g of Sr
0.571 mol of Sr

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