Transcript elements and compounds

Atoms, Elements,
Compounds and Mixtures
What is an atom?
An atom is defined as the smallest
particle of an element.
John Dalton, a British School Teacher,
proposed the atomic theory in 1802.
He tested his ideas by carrying out
experiments.
What were some of
Dalton’s ideas?
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In any element, all of the atoms are exactly
alike.
Atoms of different elements are different
Atoms of each element have a unique mass.
Daltons ideas are still used today and form the
basis of our understanding of atoms
How big are atoms?
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One grain of sand on a typical beach
contains more atoms than there are
grains of sand on the entire beach.
There are about 2,000 billion billion
(2,000,000,000,000,000,000,000) atoms
of oxygen in a drop of water.
Each dot of ink in a newspaper photo
contains about a billion billion atoms
(1,000,000,000,000,000,000)
Particles…
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Protons
Neutrons
Electrons
Subatomic Particles…
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Protons are positive +
Neutrons are neutral
Electrons are negative –
Protons and neutrons are in the center of
the nucleus
Electrons are situated in electron clouds
spinning around the nucleus
– Valence Electrons – involved in the formation of
chemical bonds – these are the outermost
electrons in the electron cloud. These can be
transferred or shared depending on the element
IONS
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An ION is an atom or group of atoms
that carry an electric charge.
So…if an atom has more protons it
is???
If there are more electrons??
What are elements?
Elements are defined as a substance
that cannot be broken down into any
other substances by chemical or
physical means.
***Elements are made up of atoms.
Where do you find
elements?
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EVERYWHERE!!!!!!!!!!!!!
All of the matter in the universe is made
from about 100 different elements.
These elements are organized to form the
Periodic Table of Elements.
Some common elements are: Oxygen
(O), Carbon (C), Hydrogen (H) and Gold
(AU)
Things to know…
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Atomic Number = the number of
protons and electrons
The difference between the atomic
number and the atomic mass = the
number of neutrons
There has to be a
pattern…
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There were only 55 elements known in
1830 – today we are up to over 100.
Dimitri Mendeleev is the man
responsible for organizing the Periodic
Table as we see it today. It is
organized in order of an increasing
atomic mass.
He also grouped elements that bonded
alike and had similar properties – he
even predicted a few.
Organizing…
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Period: a row in the
periodic table
Group or Family:
column on the periodic
table – these all have
similar properties –
some are stronger than
others…
Atomic Number – the
number of
protons/electrons in
element
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Atomic mass: average
mass of elements
atoms – usually
increases with atomic
number.
Elements higher than
93 are artificially made
Really high numbers
like 114, 116, 118, etc
– have Latin names
relating to their
location
Classification…
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Groups are typically named based on the
first element in the group: Example:
Group14 is the Carbon family.
Group 1 are metals that react violently
with water, Group 11 reacts slowly with
water, Group 17 reacts violently with
Group 1, Group 18 doesn’t really react at
all…
The table works because it based on
atoms – especially valence electrons.
What are molecules?
Molecules are defined as a combination of two
or more atoms that are bonded together.
Some molecules are made of atoms that are alike O2
(oxygen, the gas you breathe) two oxygen atoms
combine.
Other molecules are made of atoms that are different
like H2O.
BONDING…
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2 primary kinds…
IONIC – bonding of 2 oppositely
charged ions (like magnets) - positive
attracts negative and vice versa. NaCl
is an ionic bond.
Covalent – bond formed when 2 atoms
share electrons – they are attracted at
the same time. H2O is an example.
What is a Compound?
A compound is defined as a substance
made of two or more elements
chemically combined in a specific ratio.
For example, carbon dioxide gas (CO2) is
a compound made of one carbon atom
and two oxygen atoms.
What is the difference between
molecules and compounds?
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.
What is a mixture?
A mixture is two or more substances
(elements, compounds or both) that
are together in the same place but are
not chemically combined into a new
substance.
Soil is an example of a mixture because
if you look closely you can see sand
and clay in the soil sample.
How does a mixture differ
from a compound?
Two ways:
1) Substances in a mixture keep their
individual properties.
2) The parts of a mixture are not
necessarily present in specific ratios.
Atom, Molecule, or
Compound ??
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Atoms - smallest particle of an element
Element – cannot be broken down by any
means possible
Molecule – 2 or more atoms that are
bonded together. For example O2 and H2O.
Compounds – substance made of 2 or more
elements. For example: H2O
ALL compounds are also molecules, BUT all
molecules ARE NOT compounds… WHY??