Download Ch. 3 - Atomic Structure

 Mass Number
 Isotopes
 Ion
Sub atomic Particles:
particles inside an atom
 Proton = p+
 Electron = e Neutron = n0
Protons & Neutrons have
the most mass and are
located in the center of
the atom – nucleus.
Electrons are have such a
small mass – they are
considered almost
massless
Atomic # is the
number at the
top of each
block on the
periodic table
 Atomic # = #p
 Neutral Atom
#p = #e-
1
H
1.00784
 Number of protons
and neutrons in the
nucleus
 always a whole
number
 NOT on the
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Periodic Table!

mass # = protons + neutrons
Hyphen Notation: element name – mass #
 Nuclear Symbol: Mass #atomic #symbol

 Hyphen notation: carbon-12
 Nuclear symbol:
Mass #
Atomic #
12
6
C

Chlorine-37
› atomic #:
17
› mass #:
37
› # of protons:
17
› # of electrons:
17
› # of neutrons:
20
37
17
Cl
Carbon – 12
Atomic #
Mass#
#P
#E
#N
What is the same?
What is different?
Carbon – 14
Atomic #
Mass#
#P
#E
#N

Atoms of the same element with different
mass numbers.(because of different #neutrons)
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
Boron – 10
Boron – 11
Boron – 13

Which of these has more neutrons?

There are billions and billions of atoms in
any element on the periodic table.

All the atoms in element have isotopes:
same atom but with a different mass.

How do we know what the mass of all
those atoms will be?
12
12
148
12
12
12
12
12
12
14
8
12
Average
Atomic
Mass

Average Atomic mass: the
average mass of ALL the
isotopes of that element.

This number is located on
the bottom of each block
on the periodic table

Not a whole number

Different from the Mass #

Mass #: is the mass
of a single atom

Similar to a grade on
an assignment in
class.

Average Atomic Mass:
is the average mass of
billions of atoms

Similar to your average
at the end of the year –
an average of all your
assignment grades
12
12
148
12
12
12
12
12
12
14
8
12
Average
Atomic
Mass
 Models:
reasonable
representation of a very large or
a very small object.
 Atoms are very tiny and we can
not physically see the parts of an
atom – so a model (drawing) is
used to represent the atom.
 Atomic structure is an important
property of an atom and it must
be represented correctly.
 Proton
& Neutrons are in the
nucleus,
 Electrons move around the
nucleus – but they are in specific
locations around the nucleus.
 Electrons
are very tiny, have almost no
mass, and move very fast.
 The
location of an electron is hard to
identify because it moves so fast – so
electrons are modeled by an electron
cloud or ring around the nucleus.
 When
drawing models of atoms – it is
important that the electrons are drawn
in the correct ring!

The most important electrons in an atom
are the valence electrons.

Valence electrons are the electrons in
the last ring.
› Determine the ion charge
› Determine the chemical properties
› Determine the type of bonding

Drawing of an atom that includes the 3 sub
atomic particles. (drawing of the PEN table)
Protons and neutrons in nucleus
 Electrons in rings around the nucleus

› 2 electrons in 1st ring
› 8 electrons in
2nd
ring
Boron – 11
Atomic #
Mass#
#P
#E
#N
# Valence electrons

Draw a Bohr Model for the following:
Beryllium – 7
P
E
N
Magnesium – 24
P
E
N
# Valence electrons