Download Atoms, Elements, and Compounds

Atoms,
Elements, and
Compounds
Why do we study
Chemistry in Earth
Science?
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Chemistry is the study of matter.
Matter is anything that has mass and
takes up space.
All living and non living things we
study in Earth Science are made up
of matter!
ATOMS
Atoms are the building blocks
of matter!
 Atoms are very tiny but are
made up of even smaller
particles called neutrons,
protons, and electrons.
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Neutrons and Protons
Neutrons and protons are
located in the center of an
atom, called the nucleus.
 Protons are positively
charged particles.
 Neutrons are particles that
have no charge.
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Electrons
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Electrons are negatively charged
particles located outside the nucleus.
Electrons are constantly moving
around an atom’s nucleus in energy
levels.
There are an equal number of
protons and electrons in an atom, so
the overall charge is zero
How do I tell how many
protons, neutrons, and
electrons are in an atom??
1. Look at your Periodic
Table of Elements.
2. The atomic number is
the number of protons in
an atom of an element.
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Atoms must have equal
numbers of protons and
electrons…so, in our atom of
krypton, we must have 36
electrons since it contains 36
protons.
3. And the number of
neutrons is…
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The atomic weight is basically a
measurement of the total number of
particles in an atom’s nucleus.
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To find the number of
neutrons, you must first find
the mass number.
Here, Krypton’s mass number is
84 since its atomic weight, 83.80,
rounds up to 84.
The mass number is a count
of the number of particles in
an atom’s nucleus.
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What do we find in an
atom’s nucleus???
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PROTONS AND NEUTRONS!!
So,
• Mass Number= (#of
Protons)+ (# of Neutrons)
•84= 36+?
The number of
neutrons in an atom
of krypton is
48
Summary…
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For any element,
• Number of Protons= Atomic
Number
• Number of Electrons= Number of
Protons=Atomic Number
• Number of Neutrons= Mass
Number-Atomic Number
Electrons fill the energy levels
outside the nucleus.
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Level
Level
Level
Level
Level
Level
1
2
3
4
5
6
holds
holds
holds
holds
holds
holds
2 electrons.
8 electrons.
18 electrons.
32 electrons.
50 electrons.
72 electrons.
Energy levels do not have to be
completely filled to start filling the
next level.
Let’s try some on our own…
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How many protons, neutrons, and
electrons are found in each element?
• Carbon (C)
• Nitrogen (N)
• Oxygen (O)
• Phosphorus (P)
• Calcium (Ca)
• Hydrogen (H)
Atomic Radius
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size of atom
measured from center of nucleus to outside of
electron cloud
expressed in picometers (1012 pm = 1 m)
usually 40-270 pm
Example
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An atom has a radius of 140 pm.
How large is that in meters?
1m
12
10
140 pm  12
 140 10  1.4 10 m
10 pm
Now, what is an
element???
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An element is a pure substance
that cannot be broken down into
other substances by physical or
chemical means.
Elements are made of only one
type of atom.
There are 118 known elements,
94 occur naturally.
Isotopes
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Although atoms of the same element
have the same number of protons
and electrons, atoms of an element
can have different numbers of
neutrons.
Atoms of the same element that have
different numbers of neutrons are
called isotopes.
Compounds
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Elements can combine to form more
complex substances. These
substances are held together by
chemical bonds (covalent and ionic.)
A compound is a pure substance
formed when two or more different
elements combine.
Compounds have several unique
characteristics.
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Compounds are always formed from
a specific combination of elements in
a fixed ratio. Ex: H2O
Compounds are chemically and
physically different from the
elements that form them.
Compounds cannot be broken down
into simpler compounds by physical
means, such as crushing or tearing.
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Compounds can, however, be broken
down by chemical means into
simpler compounds or their original
elements.