Physical Science notes 11-14-07
The mass of a proton is 1850 times greater than the mass of an electron.
We are only concerned with the number of electro ns in the atom. They revolve around
the nucleus of an atom in energy levels or energy clouds. They are spinning around the
nucleus rapidly.
Let’s draw a schematic design of the arrangement of an atom.
P+_____
N ______
E- ______
Let’s take the element oxygen
Atomic #8, atomic mass #16
Number of electron = 8
Number of protons = 8
Number of neutrons = 8
(# neutrons = subtract the atomic # from the atomic mass)
An atom of oxygen has the following:
P8
N8
E8
Now we are concerned with these 8 electrons. They revolve around the nucleus in energy
shells.
Major Energy Shells
K
2
L
8
M
18
N
32
O
32
P
32
Q
either 1 or 2
1
Physical Science notes 11-14-07
Now oxygen has 8 electrons
Major electron configuration:
K2
L6
Oxygen has a -2 valiance number because it is lacking 2 electrons in its outer level to
make it full.
The sub-major shells are as follows
s2
p6
d 10
f 14
Oxygen has 8 electrons
Let’s plot the arrangement of electrons for the element silver (Ag)
Atomic number 47
Atomic mass 108
P 47
N 61
Put in major shells:
K
L
2
8
put in sub-major shells
s2
s2
p6
E 47
M
18
N
18
O
1
s2
p6
d10
s2
p6
d10
s1
Explain diagonal rule: fill in all sub-majors then go to the next level.
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Physical Science notes 11-14-07
Let’s plot arrangement of the electrons for the element Iodine (I) atomic number 53,
atomic mass 127
Put in the major shells
K
L
2
8
put in sub-major shells
s2
s2
p6
P 53
N 74
E 53
M
18
N
18
O
7
s2
p6
d10
s2
p6
d10
s2
p5
valiance electrons for Iodine: -1
Let’s plot the arrangement of electrons for the element uranium
Atomic number 92
Atomic mass 238
P 92
N 146
E 92
K
2
L
8
M
18
N
32
O
21
P
9
Q
2
s2
s2
p6
s2
p6
d10
s2
p6
d10
f14
s2
p6
d10
f3
s2
p6
d1
s2
3