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Vicki Hughes
Labs and Activities that go with this presentation:
Let’s Get Chemical
CHEMISTRY
ATOMS AND ELEMENTS
• Chemistry is the study of elements.
• Elements are made of atoms.
Elements = natural substances that cannot be broken
down into simpler substances.
Which one of these items is an element?
Alchemy = Chemistry
Gold was the
most fascinating
element during
the middle ages.
All matter is made up of individual particles
called atoms, which cannot be divided.
Atoms are measured in nanometers (nm).
Each atom has mass and takes up space.
John Dalton
You Can’t Touch Anything 5:29
http://www.youtube.com/watch?v=yE8rkG9Dw4s&list=PL2CA3E9D995E348E3
Matter is anything that has mass and occupies
space.
All matter is made of atoms.
Atoms are the smallest form of elements.
About 100 elements
• Hydrogen is an element that
accounts for about 90% of
total mass of the universe.
• Hydrogen makes up
about 1% of Earth’s
crust and most of that is
in water.
All of an atom’s positive charge is
concentrated in the nucleus.
Ernest Rutherford
Structure of an Atom
Proton = positive charge
Neutron = no charge
e-
The number of protons and
neutrons varies with each
element, however they are
usually equal to each other.
Electron = negative charge
Electrons are located
outside the nucleus
and are in motion.
e-
eProtons and neutrons
are grouped together
in the nucleus.
(Atomic Mass)
Atomic Number = Number of protons
Atomic Mass = protons + neutrons
# of Neutrons = Mass Number – Atomic Number
Atomic Mass?
6 + 6 = 12
# of electrons?
6 protons
balanced by 6
electrons
ISOTOPES: variations of an element
• Have a different
number of neutrons
but same number of
Protons
• Designated by the
name of the
element and its
atomic mass
number.
12
14
Normal carbon nucleus
(ACT L6 and EOG L1)
Dimitri Mendeleev
I have created a
periodic table where the
elements are arranged
according to their number
of protons. This puts
elements with similar
properties in the same
column.
Yes, clearly I am a genius!
Just watch this…
SciShow Mendeleev’s Perioidc Table
http://www.youtube.com/watch?v=wu0LixSBpk&list=UUZYTClx2T1of7BRZ86-8fow
The PERIODIC TABLE organizes the atoms of the elements
by properties and atomic number.
Atomic Numbers
PERIODIC TABLE
OF THE ELEMENTS
https://www.youtube.com/watch?v=sm1uxjGm_N0
There are over 100 elements in nature.
The Periodic Table is divided into metals, metaloids and
nonmetals.
Warning: Some periodic
tables are not color=coded!
METALS
METALOIDS
NONMETALS
Group – elements in a column with similar chemical and
physical properties.
Period – horizontal rows.
GROUP
Shows progression of the chemical
properties of the elements.
PERIOD
GROUP
Elements on the left of a period have a lower atomic mass
than elements on the right of a period.
Elements at the bottom of a group have more protons
than elements at the top of the group.
PERIOD
Properties of Metals, Metaloids, & Nonmetals
http://www.periodicvideos.com/
METALOIDS
METALS
NONMETALS
Each element has a symbol that is used only for that
element.
Symbols you should know:
Co = cobalt
C = carbon
O = oxygen
N = nitrogen
H = hydrogen
Cr = chromium
Cs = cesium
Mg = magnesium
Na = sodium
Cl = chlorine
Pb = lead
K = potassium
Symbol
6
C
12.01
Each element has a box that provide information about
that element.
Atomic #
6
Symbol
C
12.01
Atomic Mass
How do you calculate the number of neutrons?
Neutrons = Atomic Mass – Atomic Number
Atomic #
6
C
12.01
Atomic Mass
Bohr-Rutherford Diagrams
Bohr-Rutherford diagrams
are a special type of
illustration that shows the
arrangement of the electrons
around an atomic nucleus.
Octet Rule states that no
more than 8 electrons will be
assigned to any shell.
Neils Bohr
Bohr-Rutherford Diagrams
1. Draw the nucleus as a circle.
Put the number of protons (atomic number) and neutrons
(mass number - # of protons) in the nucleus.
P=19
N=20
39 – 19 = 20
The electrons are in shells (levels) around the nucleus.
1st Shell = 2 electrons
3rd Shell = 18 electrons
2nd Shell = 8 electrons
4th shell = 32 electrons
P=19
N=20
Draw the electrons by adding shells (circles) around the
nucleus. The first shell has only 2 electrons. But the
remaining shells usually have no more than 8 electrons.
e- e-
eeee- e-
ee-
ee-
P=19
N=20
eee- e-
eeee-
Practice drawing Bohr diagrams for these elements:
Calcium (Ca)
Nitrogen (N)
Oxygen (O)
Carbon (C)
ELECTRON CONFIGURATION
• Valence Electrons =
electrons in outermost shell.
Lewis Structures
Show the valence electrons in an atom – just the outmost level
Drawing Lewis Dot Diagrams
http://www.youtube.com/watch?v=ulyopnxjAZ8
3
4
5
6
7
N
Lewis Structures
H O HO
H
H
Practice drawing Lewis structures for these elements:
Calcium (Ca)
Nitrogen (N)
Oxygen (O)
Carbon (C)
Atoms are NEUTRAL if they have all of their electrons.
Carbon is neutral if it has 6 electrons.
Atomic #
6
C
12.01
Atomic Mass
8
4
5
6
7
Noble gases -- Group 8
• have full electron shells
• least likely to combine with
other elements.
MOLECULES, COMPOUNDS, and CRYSTALS (EOG L3)
•
•
Atoms gain electrons (negatives) and become more negative.
Atoms with 2-3 valence electrons will LOSE electrons and
become more positive.
Who will lose and who will gain an electron?
+
Na
Cl
Atoms have no overall electrical charge.
Ions have charges because they have gained or lost an e-.
x
+
_
Lost 1 e-
Gained 1 e-
Became positive
Became negative
Molecule = two or more atoms join together chemically.
Compound = molecule with at least two different
elements.
This is a molecule, but…
: :
: :
Molecular hydrogen (H2),
molecular oxygen (O2) and
molecular nitrogen (N2)
are not compounds
because each is composed
of only one kind of
element.
=
:
:N=N
O=O
H-H
…it is NOT a compound!
This is a molecule, AND…
Water (H2O), carbon
dioxide (CO2) and
methane (CH4) are
compounds because
each is made from more
than one element.
O
H
O=C=O
H
…it is also a compound!
The smallest bit of each of
these substances would be
referred to as a molecule.
ACT L7 (1-4 only)
EOG L2
One water (H2O) molecule
Element, Molecule, Compound, or Isotope?
1.
2.
3.
4.
5.
6.
7.
8.
water
carbon dioxide
oxygen gas (O2)
helium
carbon with an atomic mass of 12
carbon with an atomic number of 6
carbon with 8 neutrons
carbon with an atomic mass of 14
MIXTURES
A mixture is matter made up
of two or more substances
that combine physically only.
In Heterogenous Mixtures
substances are not distributed
evenly throughout the
mixture.
Cup of Lucky Charms.
In Homogenous Mixtures
substances are distributed
evenly throughout the
mixture.
Mustard, Ketchup, small cup, stirrer
Solvent is the
Solutions are homogenous
mixtures in which one
substance dissolves
completely into the other.
substance that
does the
dissolving.
Solute is the
substance that
gets dissolved.
Drink mix, water, cup, stirrer
Separation Anxiety!
How do you separate mixtures?
Sifting = separation by particle size.
Separation Anxiety!
How do you separate mixtures?
Filtration = separating a solid from a liquid in a heterogenous
mixture.
Separation Anxiety!
How do you separate mixtures?
Evaporation = separating a solid from a liquid in a solution.
PHYSICAL AND CHEMICAL CHANGES
Physical Properties Boiling Point = point at which
matter changes from a liquid to a gas.
Do you know what
“dry ice” really is?
Melting Point = point at which
matter changes from a solid to a
liquid.
Freezing Point = point at which
Solid CO2!
matter changes from a liquid to a
solid.
PHYSICAL
Properties of Matter
Shape = physical limitations.
Odor = aroma of substance.
Color = reflection of light.
Solubility = measure of the
ability to dissolve in another
substance
(Solute is what is being dissolved and
the Solvent is what is doing the
dissolving)
PHYSICAL
Properties of Matter
Conductivity = ease with which
electrons move through the material.
Magnetism = ability to be attracted
or repelled by another materials due
to a magnetic field.
Malleability = ability to be
hammered or rolled into sheets.
Ductility = ability to be pulled and
stretched into wire.
Polarity = arrangement of atoms
PHYSICAL Properties of Matter
Density = amount of mass
contained in a unit volume.
• 1. Regularly-shaped
objects use a ruler and a
balance and D=m/v
• 2. Irregularly-shaped
objects use a graduated
cylinder and a balance
and D=m/v
• 3. Liquids are compared
with other liquids.
PHYSICAL Properties of Matter
Ways to Change Matter
Density decreases as temperature increases!
Increasing Heat
Ways to Change Matter
Motion of particles increases as temperature increases!
Increasing Heat
CHEMICAL
Properties of Matter
Reactivity = ability of a material
to combine with or change into
another substance.
• Reacting to oxygen
(burning)
• Reacting to acids
pH = acidity or basicity
Combustibility = tendency to
burn
What is a chemical reaction?
A chemical reaction is the
change of a substance into a new
one that has a different chemical
identity.
How can I tell if a chemical
change is occurring?
• emission of light
• a change in temperature
• formation of a precipitate
(a solid substance that settles
to the bottom)
• evolution of a gas
• a color change
http://www.youtube.com/watch?v
=gs0j1EZJ1Uc
Glowsticks
Properties of Matter
Physical Changes
Chemical Changes
EOG L4 & L5
Any
Questions?