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Atomic Structure Nucleus- center of an atom -contains protons
(which are positive) -contains neutrons
(which are neutral)
Ex- Sodium:
Atomic StructureOutside 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 600,000,000,000,000,000,000,000 amus in one gram.
(Remember that electrons are 2000 times smaller than one amu).
Subatomic Particles Organized
Charge Location Mass
Protons
Neutrons
Electrons
Subatomic Particle Organized
Charge Location Mass
Protons Positive In nucleus 1 amu
Neutrons Neutral In nucleus 1 amu
Electrons Negative Outside of nucleus/ in energy levels
0 amu
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
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.
C Carbon
CuCopper
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 # of protons
# of neutrons
Atomic # Mass # # of electrons
A
B
C
D
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 3B 11 12 11 23 11C 19 20 19 39 19D 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 #
Atomic #
Mass hyphen notation: Symbol- Mass ex: N-14
Symbol
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 isotopeEx’s
C-14 C-12
How to write isotopes…
Nuclear Symbol Notation Includes the symbol, atomic #, and the mass
# for that isotopeEx’s
14
6CMass #
Atomic # (=p)
How do we Draw Atoms?
Bohr Models Lewis Dot Diagrams
How to draw a Bohr Model1. Draw a nucleus & put protons and neutrons inside.
(may use a square shape so you don’t draw any electrons on it)
2. 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 shellUse 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 Structure1. Use the group # (top of the row on the
PT) to determine # of valence electrons
2. Write the symbol.
3. 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 Structure1. Find the group # (top of the row on the PT)
Let’s do Phosphorus
2. Write the symbol. P
3. 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 Organizes elements in a particular way
All 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.
Let’s Color
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
Solid non-metals are brittle and break easily.
dull. Many non-metals are
gases.
Sulfur
Properties of Metalloids/Semiconductors
Metalloids (metal-like) have properties of both metals and non-metals. They are solids that can be
shiny or dull. They conduct heat and
electricity better than non-metals but not as well as metals.
They are ductile and malleable.
Silicon
Families Periods 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.
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 133 valence electrons
Carbon Family- group 144 valence electrons
Nitrogen Family- group 155 valence electrons
Oxygen Family- group 166 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)
Ex-
A 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)
Ex-A 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 CHARGEGet 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 chargeMeans you added an electron!
CATION- has a positive chargeMeans you lost an electron
