Transcript Understanding the differences and relationships of Atoms

Understanding the differences
and relationships of
Atoms, Elements,
Molecules, and Compounds
http://education.jlab.org/qa/atoms_and_elements.html
What are atoms?
• Atoms are the smallest bits of ordinary matter
and are made from particles
called protons (which carry a positive electrical
charge), neutrons (which carry no electrical
charge) and electrons (which carry a negative
electrical charge).
• The protons and neutrons cluster together in the
central part of the atom, called the nucleus, and
the electrons 'orbit' the nucleus.
• A particular atom will have the same number of
protons and electrons and most atoms have at
least as many neutrons as protons.
What are Isotopes?
• If you had very, very good eyes and could look at the
atoms in a sample of hydrogen, you would notice that
most of the atoms have no neutrons, some of them
have one neutron and a few of them have two
neutrons. These different versions of hydrogen are
called isotopes.
• All isotopes of a particular element have the same
number of protons, but can have different numbers of
neutrons. If you change the number of protons an
atom has, you change the type of element it is. If you
change the number of neutrons an atom has, you make
an isotope of that element.
What is an element?
• An element is a substance that is made
entirely from one type of atom.
– For example, the element hydrogen is made from
atoms containing just one proton and one
electron.
• All known elements are arranged on a chart
called the Periodic Table of Elements.
What is a compound?
• A compound is a substance made from two or
more different elements that have been
chemically joined.
• Some examples of compounds are water
(H2O), table salt (NaCl), table sugar (C12H22O11)
and chalk (CaCO3).
What is a mixture?
• A mixture is a substance made by combining
two or more different materials in such a way
that no chemical reaction occurs.
• A mixture can usually be separated back into
its original components.
• Some examples of mixtures are a tossed salad,
salt water and a mixed bag of M&M's candy.
What is the difference between a
compound and a molecule?
• A molecule is formed when two or more atoms join together
chemically. A compound is a molecule that contains at least
two different elements. All compounds are molecules but not
all molecules are compounds.
• Molecular hydrogen (H2), molecular oxygen (O2) and
molecular 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 would be
referred to as a molecule. For example, a single molecule of
molecular 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.
More on molecules and compounds…
• A molecule is what you get when any atoms join together.
• A compound is what you get when atoms of two or more
different elements join together.
• All compounds are molecules, but not all molecules are
compounds.
• Water is a molecule because it is made from atoms that
have been chemically combined. It is also a compound
because the atoms that make water are not all the same some are oxygen and some are hydrogen.
• Oxygen in the atmosphere is a molecule because it is made
from two atoms of oxygen. It is not a compound because it
is made from atoms of only one element - oxygen. This type
of molecule is called a diatomic molecule, a molecule made
from two atoms of the same type.
• Imagine going to an ice cream store. Let's say that they
have 30 different flavors of ice cream. Those are elements,
the things that I have available to build my dessert from.
The smallest amount of ice cream that the store will sell to
me is a scoop. This is an atom. If I want, I can put two or
more scoops of ice cream together. This is a molecule. If my
molecule has more than one flavor of ice cream, I can call it
a compound.
– element - a basic substance that can't be simplified
(hydrogen, oxygen, gold, etc...)
– atom - the smallest amount of an element
– molecule - two or more atoms that are chemically joined
together (H2, O2, H2O, etc...)
– compound - a molecule that contains more than one element
(H2O, C6H12O6, etc...)
• What's wrong with the ice cream analogy? Splitting an
atom creates different elements (split an oxygen atom and
you don't have oxygen any longer). Splitting a scoop of ice
cream results in smaller blobs of the same flavor. For the
analogy to hold true, the flavor of the ice cream would have
to change when you split a scoop (the chocolate 'element'
would have to change into some other 'element' (flavor)).
Carbon (C)
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The Element Carbon
6
C
Carbon
12.0107
Atomic Number: 6
Atomic Weight: 12.0107
Melting Point: 3823 K (3550°C or 6422°F)
Boiling Point: 4098 K (3825°C or 6917°F)
Density: 2.2670 grams per cubic centimeter
Phase at Room Temperature: Solid
Element Classification: Non-metal
Period Number: 2 Group Number: 14 Group Name: none
What's in a name? From the Latin word for charcoal, carbo.
Say what? Carbon is pronounced as KAR-ben.
Carbon, the sixth most abundant element in the universe, has been known since ancient times. Carbon is most commonly
obtained from coal deposits, although it usually must be Estimated Crustal Abundance: 2.00×102 milligrams per kilogram
Number of Stable Isotopes: 2 (View all isotope data)