Transcript Element - Bardstown City Schools

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Scientist used to
believe that matter was
made up of four
elements (air, earth,
fire and water).
We now know that all
matter in the universe
is made of slightly
more than 100
different substances
called elements.
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Element - a pure
substance that
cannot be broken
down into any other
substances by
chemical or physical
means.
Gold
Elements are the
simplest substances.
Copper
Iron
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The elements do not
only exist alone …
they combine with
other elements to
make all the matter in
the world.
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The six elements found
in the amount in living
things are:
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All living things,
including humans, are
made mostly of just
six elements
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Nitrogen
Carbon
Hydrogen
Oxygen
Phosphorous
Sulfur
The way to remember it
this is N’CHOPS. Pork
Chops, N’CHOPS
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Mendeleev is best
known for his work
on the periodic table;
arranging the 63
known elements into
a Periodic Table based
on their mass
He lived from 18341907
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Atomic number is on top
The symbol is in the
middle.
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Can be one capital letter
like “O” for oxygen
Can be one capital letter
and one lowercase like
“Au” for gold when there
are two letter abbreviations.
Element name MAY OR
MAY NOT BE LISTED
WITH THE SYMBOL!
The atomic mass is below
the symbol.
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The periodic table was originally organized by increasing
mass (Mendeleev).
The modern periodic table is organized by increasing
atomic number.
The number starts at 1 with Hydrogen, increases going to
the right with Helium, 2.
It then jumps down a row and starts to the far left with
Lithium, 3 and continues with this pattern until you get
to the sixth row and we will discuss.
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Period – the name for each row of elements
(left to right)
Family – the name for each column of element (
up and down)
THE PERIODIC TABLE PICTURES
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What is the smallest
possible piece of
matter?
All matter is made up
of atoms.
Atom - is the basic
particle from which
all elements are
made.
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All atoms are made of the same 3 subatomic
(smaller than an atom) particles.
•Protons
•Electrons
•Neutrons
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Different elements
have different
properties because
their atoms are
different.
The hydrogen atom
has 1 proton and 1
electron
The helium atom has 2
protons, 2 neutrons,
and 2 electrons.
•Atoms are made of protons
(+), neutrons (no chargeneutral), and electrons (-).
•The number of protons
determines which elements
can be formed from the atoms
•Remember, the atomic
number of an element tells
you the number of protons in
that element
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Atoms of most elements have the ability to combine
with other atoms.
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When atoms combine, they form a chemical bond,
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Chemical Bond - a force of attraction between two
atoms.
In many cases, atoms combine to form larger
particles called molecules.
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Molecules – when two or more atoms join together
by chemical bonds.
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 For Example: A molecule of water is made of a 2 different
elements and three atoms total, H2O.
 H – 2 atoms of Hydrogen as shown by the subscript 2
 O – 1 atom of Oxygen (anytime there is not a subscript after an
element, it is assumed to be a 1) (we will discuss this again)
Two atoms of the same element can also combine to
form a molecule.
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Oxygen molecules consist of two oxygen atoms.
There are 7 elements that combine to form DIATOMIC
molecules in nature – Hydrogen (H2), Nitrogen (N2),
Oxygen (O2), Fluorine (F2), Chlorine (Cl2), Bromine (Br2),
and Iodine (I2)
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Compound - a molecule that contains at least two different elements
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All compounds are molecules BUT not all molecules are compounds.
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Remember…..A molecule is formed when two or more atoms join
together chemically.
Diatomic hydrogen (H2), diatomic oxygen(O2) and diatomic nitrogen
(N2) are not compounds because each is composed of a SINGLE element.
Water (H2O), carbon dioxide (CO2) and methane (CH4) are compounds
because each is made from more than one element.
The smallest bit of each of these substances (COMPOUNDS) would be
referred to as a molecule.
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For example, a single molecule of diatomic hydrogen is made from two atoms of
hydrogen while a single molecule of water is made from two atoms of hydrogen
and one atom of oxygen.
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CO2
The number 2 below the
symbol for oxygen tells you
that the ratio of carbon to
oxygen is 1 to 2.
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There is 1 Carbon atom
for every 2 Oxygen atoms.
(Anytime there is not a
subscript after an element,
it is assumed to be a 1)
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If a different ratio of carbon
atoms to oxygen atoms are seen
in a formula, you have a
different compound.
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CO
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Carbon to oxygen ratio is 1 to 1.
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There is 1 Carbon atom for
every 1 Oxygen atom.
For example, Carbon Monoxide
– a gas produced in car engines
– has the formula CO.
Carbon Dioxide – a gas we
exhale – has the formula CO2
When elements are chemically combined, they form
compounds having properties that are different from
those of the uncombined elements.
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SULFUR AND SILVER UNCOMBINED
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For example, the element
sulfur is a yellow solid and
the element silver is a
shiny metal.
SULFUR AND SILVER –
BONDED IN A COMPOUND
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When silver and sulfur
combine, they form a
compound called silver
sulfide, Ag2S. You would call
this black compound tarnish.