Atomic
Composition
Unit 3 –
Nuclear Model of the atom
What do we know about atoms?
The atom is made of subatomic particles
called nucleons.
There are different types of nucleons
3 Major Subatomic Particles
ELECTRON
e-
Negatively Charged
Atomic Mass – 0.0005 amu
Basically round to zero amu
PROTON
p+
Positive Charge
Mass of 1.007 amu
Found in nucleus of atom
Neutron no
No charge - “neutral”
Mass of 1.0009 amu
Found in Nucleus
Other Subatomic
Particles
Computer Generated
picture of two bombarded
atoms.
Symbol -Z
All atoms of the
same element
have the same
number of
protons in the
nucleus.
ATOMIC NUMBER =
NUMBER OF PROTONS
Symbol -A
Mass comes from the nucleus of the atom.
Mass number = # protons + # neutrons
No overall Charge
Number of
protons and
electrons are the
same
Number of
neutrons = mass
number minus
atomic number
Nitrogen
?protons, neutrons,
electrons
Copper
?protons, neutrons,
electrons
PROTONS = 7
PROTONS = 29
NEUTRONS= 7
NEUTRONS= 35
ELECTRONS= 7
ELECTRONS= 29
Ion
There was either:
1. Gain of electron(s)
X
1. Loss of electron(s)
X+
Calculating
nucleons in an ion
If an atom is not
electrically neutral than
there is an imbalance of
the proton to electron
ratio and we have an ion.
If we have an ion one of
two scenarios are
present:
Protons are in greater
number than electrons so
we have a positive ion.
Protons are in less
number than electrons so
we have a negative ion.
 Example: How many
protons, neutrons
and electrons are
there in Mg +2 In an
atom or ion the
number of protons is
always the same.
(atomic number)
 Calculating the number
Mg +2
?proton neutrons electrons
In an atom or ion
the number of
protons is always
the same. (atomic
number)
of neutrons is the Mass
number minus the
atomic number
 Calculating electrons in
an ion we have to look
at the charge on the
ion. If the ion is positive
then there are more
protons than electrons
and if the number is
negative then there are
more electrons than
protons
 Magnesium has a mass
Mg
+2
?proton neutrons electrons
Magnesium has an
atomic number of 12
so the
PROTONS = 12
number of 24 so the
NEUTRONS =
24 (mass #) – 12(atomic #) = 12
 Magnesium has a charge of a
+2 so the number of protons
are 2 more than the number
of electrons. Since the
number of protons does not
change we will subtract 2
from the atomic number to
give us ELECTRONS=
12 (atomic #) -2(the number on
the charge = 10 the number of
electrons.
Al+3
?proton neutrons electrons
O-2
?proton neutrons electrons
PROTON = 13
PROTON = 8
NEUTRON = 27-13=14
NEUTRON = 16-8=8
ELECTRON = 13-3=10
ELECTRON = 8+2=10
METALS LOSE ELECTRONS
BECOMING POSITIVELY CHARGED.
NONMETALS GAIN ELECTRONS
BECOMING NEGATIVELY CHARGED.
How do we write all of this
information?
3. Add the # of
neutrons to the
number of protons.
REMEMBER - this is
the atomic mass.
Complete Chemical
Symbol
Write the symbol for the
atom with 28 protons, 28
electrons and 31 neutrons.
Ni
28
59
4. Check to see if
you have an atom or
ion.
the number
2. Write
1. an
the
Look
number
upIfthe
orin
protons
does
not
of protons
symbol
the
by using
the
equal
the
number of
lower left
number
handof
side
protons.
electrons then
of the REMEMBER:
element.
the you
will need
to add ais+
number
of protons
or the
a – charge.
thecharge
same as
atomic number.
How do we write all of this
information?
3. Add the # of
neutrons to the
number of protons.
REMEMBER - this is
the atomic mass.
Complete Chemical
Symbol
Write the symbol for the ion
with 8 protons, 10 electrons
and 8 neutrons.
O
8
16
-2
4. Check to see if
you have an atom or
ion.
the number
2. Write
1. an
the
Look
number
upIfthe
orin
protons
does
not
of protons
symbol
the
by using
the
equal
the
number of
lower left
number
handof
side
protons.
electrons then
of the REMEMBER:
element.
the you
will need
to add ais+
number
of protons
or the
a – charge.
thecharge
same as
atomic number.
How do we write all of this
information?
3. Add the # of
neutrons to the
number of protons.
REMEMBER - this is
the atomic mass.
Complete Chemical
Symbol
Write the symbol for the ion
with 20 protons, 18 electrons
and 20 neutrons.
+2
Ca
20
40
4. Check to see if
you have an atom or
ion.
the number
2. Write
1. an
the
Look
number
upIfthe
orin
protons
does
not
of protons
symbol
the
by using
the
equal
the
number of
lower left
number
handof
side
protons.
electrons then
of the REMEMBER:
element.
the you
will need
to add ais+
number
of protons
or the
a – charge.
thecharge
same as
atomic number.
How do we write all of this
information?
Element name – atomic mass
How many protons, neutrons
and electrons are in
Tantalum-181.
Protons – 73
Electrons – 73
1. The number of
protons comes from
the atomic
2.number.
The number of
Neutrons
– 108
electrons equals the
number protons
because this is a
neutral atom.
3. The number of
neutrons is equal to
the mass number
minus the atomic
number.
Now it your turn to practice
Complete the in class practice WS
Example Using the Bohr Model
1s22s22p63s1
Na is a metal and wants to lose
an electron so it has a full energy
level of electrons.
1s22s22p63s23p5
Cl is a nonmetal and wants to gain and
electron so it can have a full energy
level.
Example Using the Bohr Model
1s22s22p6
11 protons and 10 electrons
make an ion with a +1 charge.
1s22s22p63s23p6
17 protons and 18 electrons
make an ion with a -1 charge.