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Atoms
Atom
• smallest part of element that has all
properties of the element
• If you break an atom apart into sub-atomic
particles, they no longer have the properties
of the element
– For example, if you take a lump of coal (the
element carbon), and break it into smaller and
smaller pieces, the smallest piece that still acts
like coal is one atom of carbon.
Parts of an Atom
• 2 main parts
– nucleus
– electron cloud.
• Most space between
nucleus and electron
cloud is empty
Electron
Cloud
Nucleus
• Nucleus is located in the center of
the atom
• 2 subatomic particles:
– Protons
– Neutrons
+ Protons +
Sub-atomic particle
•
•
•
•
Charge = + (positive)
Mass = 1 amu
Location = nucleus
Every atom of an element has the
same number of protons
• Protons IDENTIFY the element…no
two elements can have the same
number of protons….
= Neutrons =
Sub-atomic particle
• Charge = 0 (neutral)
• mass = 1 amu
• Location = nucleus
• Number of
neutrons in an
element can vary
- Electron Sub-atomic particle
• Charge = - (negative)
• mass ≅ 0.005 amu
– 1836 electrons = mass 1 proton
• Location = electron cloud outside &
around nucleus
Periods
•Each row is called a “period”
•The elements in each period have
the same number of shells
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Groups
Except for He, it
has 2 electrons
•Each column is
called a “group”
•Each element in a
group has the same
number of electrons
in their outer orbital,
also known as
“shells”.
•The electrons in the
outer shell are called
“valence electrons”
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Element
Properties
METALLOIDS
NON METALS
METALS
3 categories on the
periodic table:
o 1. Metals
(left)
o 2. Metalloids
(zig zag)
o 3. Nonmetals
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Parts of an Atom
Electron
Cloud
Protons
Neutrons
Electrons are what determines
how an atom reacts
ato
m
But where exactly are
the
electrons inside an
atom?
Orbitals
areas within atoms
where there is a high
probability
of finding electrons
Orbital Levels
• closest to nucleus – max 2
electrons
• 2nd shell – max 8 electrons
• 3rd shell – max 8 electrons
• fill shells closest to nucleus
first
Hydrogen
NUCLEUS
Helium
-
-
NUCLEUS
Lithium
-
-
NUCLEUS
Beryllium
-
-
NUCLEUS
-
Boron
-
-
NUCLEUS
-
-
Carbon
-
-
NUCLEUS
-
-
Nitrogen
- -
-
NUCLEUS
-
-
Oxygen
- -
-
NUCLEUS
- -
-
Fluorine
- -
-
NUCLEUS
- -
-
Neon
- -
-
NUCLEUS
- -
-
Sodium
-
- -
-
-
NUCLEUS
- -
-
Magnesium
-
- -
-
-
NUCLEUS
- -
-
Aluminum
-
- -
-
-
-
NUCLEUS
- -
-
Silicon
-
- -
-
-
-
NUCLEUS
- -
-
Phosphorus
-
-
- -
-
-
-
NUCLEUS
- -
-
Sulfer
-
-
- -
-
-
-
NUCLEUS
- -
-
-
Chlorine
-
-
- -
-
-
-
NUCLEUS
- -
-
-
Argon
-
-
- -
-
-
NUCLEUS
-
-
-
- -
-
-
Science has determined where
the orbitals are inside an atom,
but it is never known precisely
where the electrons are inside
the orbitals
Because of this unknown we call
the orbitals an “electron cloud”
Knowing how electrons are
arranged in an atom is
important
because that controls how
atoms react with each other to
form molecules
HAPPY ATOMS
• valence number – number of
electrons in outer most shell of
atom
• Atoms want outer most shell to be
full, will lose or gain extra electrons
Sodium
-
VALENCE
-
--
-
-
NUCLEUS
--
-
Chlorine
-
-
--
-
-
-
NUCLEUS
--
-
-
-
Sodium
Chloride
Sodium
Chlorine
“SALT” --
-
--
NUCLEUS
--
-
--
-
-
--
NUCLEUS
-
--
-
-
Molecule
two or
more atoms
that are
chemically
bonded
NaCl
H2O
O2
SO4
H2
CO2
N2
O3
Compound
two or more
different
elements
that are
chemically
bonded