Intro to Chemistry
Atomic Structure

Nucleus- center of an atom
-contains protons
(which are positive)
-contains neutrons
(which are neutral)
Ex- Sodium:
Atomic Structure
Outside the Nucleus:
 Electrons (which are negative) surround
the nucleus in energy levels
 Outermost electrons are called valence
electrons
An atom is defined by the
number of PROTONS IT HAS!!!
Atomic Mass Unit (AMU)


The unit of
measurement for an
atom is an AMU. It
stands for atomic
mass unit.
One AMU is equal
to the mass of one
proton.
Atomic Mass Unit (AMU)


There are
6 X 1023 or
600,000,000,000,000,0
00,000,000 amus in
one gram.
(Remember that
electrons are 2000
times smaller than one
amu).
Subatomic Particles Organized
Charge
Protons
Neutrons
Electrons
Location
Mass
Subatomic Particle Organized
Protons
Charge
Location
Mass
Positive
In nucleus
1 amu
Neutrons
Neutral
In nucleus
1 amu
Electrons
Negative
Outside of
0 amu
nucleus/ in
energy levels
Atomic
Mass
Try it out!
Read pp 104-108
then do #3, 4, 5 on page 110
The Periodic Table can
tell us a lot about the
elements.
What’s in a square?

Chemical Symbol- letter representing the atom
(sometimes from Latin)

ALWAYS write the first letter capital and second letter
lower case

Ex- Cu, Fe, Rb
Symbols
C

Carbon
Cu
Copper

All elements have
their own unique
symbol.
It can consist of a
single capital letter,
or a capital letter
and one or two
lower case letters.

Atomic number = number of protons


Don’t kill anyone in my class today!
Mass number = # protons + # neutrons

Don’t use the one on the PT unless you have to! That is an
average! Use the Mass # given for that element!
Calculating Neutrons is a simple
algebraic problem…
Atomic Mass = protons + neutrons
 Atomic Number = protons
 Write the equation…

 Mass
# = protons + neutrons
 #Neutrons = (mass number – atomic number)
What about Electrons?
In a NEUTRAL atom, every + (proton) is
balanced by a –(electron).
 Therefore, in a neutral atom,
protons=electrons and you can use the
following mneumonic:

A = P
=E
(atomic #) = (protons) = (electrons)
Complete the table below using the information given for each atom.
Atom A has 3 protons and 4 neutrons.
Atom B has 11 protons and 12 neutrons.
Atom C has an atomic number of 19 and a mass number of 39.
Atom D has an atomic number of 17 and a mass number of 35.
Atom
A
B
C
D
# of
protons
# of
neutrons
Atomic # Mass #
# of
electrons
Complete the table below using the information given for each atom.
Atom A has 3 protons and 4 neutrons.
Atom B has 11 protons and 12 neutrons.
Atom C has an atomic number of 19 and a mass number of 39.
Atom D has an atomic number of 17 and a mass number of 35.
Atom
# of protons # of
neutrons
Atomic # Mass #
# of electrons
A
3
4
3
7
3
B
11
12
11
23
11
C
19
20
19
39
19
D
17
18
17
35
17
Try it out!
(Blue Worksheet)
 Check answers at front…move onto yellow
sheet if doing well
 NEED TO KNOW…

 Nuclear
Symbol notation:
Mass #

Symbol
Atomic #
 Mass

hyphen notation:
Symbol- Mass
ex:
N-14
Atomic Mass Mystery…

Look at the atomic mass for Oxygen.
What does it say (exactly?)
 15.9999

What is the atomic mass?
P

+N
So what the heck!?!?!
 Average
of the actual isotopes on Earth!!!
How can we change the mass
of an element?

We can’t mess with protons, but what
CAN we “mess with?”
 Neutrons…
What would that change about the atom?
 Changes the MASS
 Get an ISOTOPE

Isotopes
Isotopes are different atoms of the same
element that contain the same number of
protons but different number of neutrons.
 Examples

Cl-35
vs.
Cl-37
17P
17P
18N
20N

How to write isotopes…

Mass/Hyphen Notation:
 Especially
important for a form of the isotope
that is NOT the “usual”
 Write the symbol, a dash, and the mass # for
that isotope
 Ex’s
C-14
 C-12

How to write isotopes…

Nuclear Symbol Notation
 Includes
the symbol, atomic #, and the mass
# for that isotope
 Ex’s
14
Mass #
Atomic # (=p)
6
C
How do we Draw Atoms?

Bohr Models

Lewis Dot
Diagrams
How to draw a Bohr Model
1.
Draw a nucleus & put protons and neutrons inside.

2.
(may use a square shape so you don’t draw any electrons
on it)
Remember the p=e in a neutral atom, so begin
putting electrons on the energy levels until you use
them all up.

Fill energy levels in order (can’t put any in 2nd shell until
you’ve filled the first)
Drawing Bohr models, cont…
Helpful hints:
1. Draw electrons at each of the four “corners”, then
double up
2. Write the number of electrons you drew (in
parentheses) on each energy level to help you keep
track.
Electron configurations (Bohr Models)

But…that can be a pain…
Most of the time we only really care about
the valence electrons
 Valence Electrons- electrons in the
outermost shell

 Use
the GROUP NUMBER!!!
Valence Electrons
Find the number of valence electrons by
counting over the rows (skipping transition
metals)

Notice- rows 13, 14, 15, 16, 17, 18 have 3,
4, 5, 6, 7, and 8 valence electrons
respectively.
Valence Electrons are what
react!
How to draw a Lewis Dot
Structure
1.
2.
3.
Use the group # (top of the row on the
PT) to determine # of valence electrons
Write the symbol.
Draw dots around the symbol equal to the
# of valence electrons (if group 2- draw
two dots)
1.
Place dots one at a time around the top,
right, bottom and left side of the atom before
you double any up.
How to draw a Lewis Dot Structure
1.
2.
3.
Find the group # (top of the row on the PT)
Let’s do Phosphorus
Write the symbol. P
Draw dots around the symbol equal to the
group number (if group 2- draw two dots)
1.
Place dots one at a time around the top, right,
bottom and left side of the atom before you double
any up.
Octet Rule
Most atoms want to have 8 electrons in
their outer shell.
Octet rule exceptions…
(octet rule=Most atoms want to have 8
electrons in their outer shell)
 Helium
 What
is its group number?
 Why doesn’t it make sense to draw that many
dots?
 Because it only has 2 electrons TOTAL!
Elements with a full outer shell
naturally
Lewis Dot Structures
Families on the
Periodic Table
Elements


Science has come a
long way since
Aristotle’s theory of Air,
Water, Fire, and Earth.
Scientists have
identified 90 naturally
occurring elements,
and created about 28
others.
Elements

The elements,
alone or in
combinations, make
up our bodies, our
world, our sun, and
in fact, the entire
universe.
Mendeleev



In 1869, Dmitri Ivanovitch Mendeléev
created the first accepted version of
the periodic table.
He grouped elements according to
their atomic mass, and as he did, he
found that the families had similar
chemical properties.
Blank spaces were left open to add
the new elements he predicted would
occur.
Periodic Table

All
Organizes elements in a particular way
the elements in this column
(“family”) have similar properties.
That’s why they are grouped
together.
EX- Valence electrons can be
determined from the group number!
What does it mean to be
reactive?
We will be describing elements
according to their reactivity.
 “Reactive
Elements” do not have a full
outer shell of electrons. Therefore,
they will “react” with other elements to
get a full outer shell.
First let’s draw our staircase in
black…
Make a chart

Metals

Nonmetals
Properties of Metals

Physical Properties of
Metals…






Solid at room temperature
good conductors of heat and
electricity.
shiny.
ductile (can be stretched into
thin wires).
malleable (can be pounded into
thin sheets).
A chemical property of many
metal is its reaction with
water which results in
corrosion. (rust)
Properties of Non-Metals

Physical properties of
Non-metals …


poor conductors of heat
and electricity.
not ductile or malleable



Sulfur
Solid non-metals
are brittle and
break easily.
dull.
Many non-metals are
gases.
Properties of
Metalloids/Semiconductors

Metalloids (metal-like)
have properties of both
metals and non-metals.



Silicon
They are solids that can be
shiny or dull.
They conduct heat and
electricity better than nonmetals but not as well as
metals.
They are ductile and
malleable.
Families


Columns of elements are
called groups or families.
Elements in each family
have similar but not
identical properties.


For example, lithium (Li),
sodium (Na), potassium (K),
and other members of family
IA are all soft, white, shiny
metals.
All elements in a family
have the same number of
valence electrons.
Periods


Each horizontal row of
elements is called a period.
The elements in a period
are not alike in properties.


In fact, the properties change
greatly across even given
row.
The first element in a period
is always an extremely active
solid. The last element in a
period, is always an inactive
gas.
Hydrogen


Hydrogen is in a family of its own.
It’s a nonmetal on the metal’s side
 It’s
a gas at room temperature.
Alkali Metals





Group one
the first column of the
periodic table.
1 valence electron.
All metal properties (They
are shiny, etc)
Soft metals: easily cut with
a knife.
Alkali Metals





They are the most reactive metals.
They react violently with water.
http://www.youtube.com/watch?v=uqDWbknpi
Vk
http://www.youtube.com/watch?v=92Mfric7JUc
Alkali metals are never found as free
elements in nature. They are always bonded
with another element.
Use Purple
Alkaline Earth Metals





Group 2
Second column of metals
(Properties of metals)
Also very reactive (but not as reactive as
Alkali metals)
They have two valence electrons.
Transition Metals

Big group in the middle.



(group varies)
Properties of metals.
(They are good conductors
of heat and electricity, etc.)
Everything else varies
(valence electrons,
reactivity, etc)
Use orange
Halogen Family



Group 17
Second column from the
right.
Halogens have 7
valence electrons,
which explains why they
are the most reactive
non-metals. They are
never found free in
nature.
They react with alkali metals to
form salts.
Use Red
Noble Gases




Group 18
8 valence electrons
colorless gases
extremely un-reactive.



Becauses their outermost energy level is full.
called inert.
Rare Earth Elements


The thirty rare earth
elements are composed
of the lanthanide and
actinide series.
One element of the
lanthanide series and
most of the elements in
the actinide series are
called trans-uranium,
which means synthetic or
man-made.
The next 4 families are named by the
element at the top of the row

Boron Family- group 13
3

Carbon Family- group 14
4

valence electrons
Nitrogen Family- group 15
5

valence electrons
valence electrons
Oxygen Family- group 16
6
valence electrons
Predicting Ion
Formation
Let’s look at our families- What ion
will each form?

It all starts with the noble gases…
Everyone wants to be NOBLE
These are the “magic numbers”
Each of these atomic numbers will make a
“full outer shell”
 Other families will lose or gain electrons to
get the these “numbers”

Alkali Metals

All (except hydrogen- of course) will lose
one electron to form a __________
charge.

(+1)
Alkaline Earth Metals

All will lose two electrons to form a __________
charge.

(+2)
ExA neutral Mg atom has 12 protons and 12 electrons
(+12) + (-12) = 0
A Mg ion has 12 protons and only 10 electrons
(+12) + (-10) = +2
Boron Family

All will lose three electron to form a ____
charge.

(+3)
Carbon Family is special

All have four valence electrons, so it can
lose four OR gain four to fulfill its octet!
So it can form a _____ or a ______ion!
-(+4) or (-4)
Nitrogen Family

All have five valence electrons, so it can
gain three to fulfill its octet!
So it can form a ________ion!
- (-3)
Oxygen Family

All will gain two electrons to form a __________
charge.

(-2)
ExA neutral Oxygen atom has 8 protons and 8 electrons
(+8) + (-8) = 0
An Oxygen ion has 8 protons and 10 electrons
(+8) + (-10) = (-2)
HALOGENS

All will gain one electrons to form a
__________ charge.

(-1)
How about those noble gases?

They will NOT FORM IONS!!!
What subatomic particles CAN
we “mess with?”

Already know…Neutrons…
 Get

an ISOTOPE, changes the mass
But what if I mess with Electrons…
 What
would that change about the atom?
 Changes the CHARGE
 Get an ION
Intro to Ions
How are these ions made?





Can you mess with protons?
Would messing with neutrons do
anything to the charge?
What must you mess with???
What charge does an electron
have?
So what would happen to the
atom if they LOSE one? Would
they get more positive or more
negative overall???
IONS
If you mess with the electrons you change
the overall charge of the atom…an atom
that is no longer neutral is called an ION.
 ANION- has a negative charge

 Means

you added an electron!
CATION- has a positive charge
 Means
you lost an electron