Atomic Theory Class #1
Penny Lab ASAP.
Check your grades!
OB: Students will examine basic
structure of the atom, learn what the
numbers on the Periodic table mean, and
look at electron orbitals.
Take out your WHITE periodic tables now.
All atoms are made up of three sub-atomic (smaller than atoms) parts. They are the
Parts of
the atom
Particle
Charge
Symbol
Mass
Location
All atoms are made up of three sub-atomic (smaller than atoms) parts. They are the
Parts of
the atom
proton
Particle
Charge
Symbol
Mass
Location
+
+
p
1 amu
nucleus
zero in
high
school
Flying
around the
nucleus
1 amu
nucleus
electron
-
e
neutron
Ø
n°
The mass of an electron is NOT ZERO, but it’s so small, about 1/1750 of a proton or
neutron, that we will disregard it’s mass. It’s an intro class, and we can’t measure these
masses in our class anyway, but it’s not really zero in the real world.
The nucleus is the small, dense center of an atom where the protons and neutrons live.
Electrons fly around outside, relatively far away.
In this model, the nucleus is the
yellow ball in the middle. It
does not show it, but inside must
be three protons and probably 4
neutrons.
This is a model of atom #3, which
is LITHIUM.
It’s a cartoon, it’s not even
what we think atoms look like,
but it’s cute.
The mass of all atoms are measured in super tiny masses
called AMU, or ATOMIC MASS UNITS.
The vocabulary is building up already. This is another topic
to NOT FALL BEHIND ON.
Masses for the subatomic particles (approximate)
Protons = 1 amu each
Neutrons = 1 amu each
Electrons = zero mass in high school chem
Atomic
Mass
Atomic
Number
Electron
Configuration
12.011
6
2-4
Atomic Mass Numbers will be rounded to the nearest
whole number (they are not really whole numbers, we’ll
get to that later)
Mass Number = mass of protons plus neutrons
Mass = p+ plus n°
The mass of mercury is 201, so mercury has a
total of 201 protons plus neutrons.
How many of each??? Let’s learn how to figure
this out
Atomic Mass of Hg = 201 amu
Minus the protons
Equals the n°
which is the total
number of p+ plus n°
- 80 p+
121 n°
the n° + p+ = mass
Let’s do TIN, Sn
An atom of tin = 119 amu which is the total p+ + n°
Minus atomic # - 50
which is the # p+
69 left over, which are the neutrons
Mass = p+ and n°
Minus atomic number =
- p+
Equals number of neutrons = n°
All atoms are electrically neutral,
The number of p+ = e-
The positives = the negatives.
Always.
Every atom is neutrally
charged. The positive protons +
negative electrons BALANCE.
How many p+, n° and e- are in these atoms?
In
Nb
Ba
How many p+, n° and e- are in these atoms?
In
Nb
Ba
Mass = 115
Mass = 93
Mass = 137
Minus the At # - 49
Minus the At # - 41
Minus the At # - 56
Neutrons = 66
Neutrons = 52
Neutrons = 81
Calcium can also be written properly as:
Atomic mass
Atomic number
40
20
Ca
Write the Formal Symbols for these atoms:
mercury, chlorine, and copper
Calcium can also be written properly as:
40
20
Atomic mass
Atomic number
Ca
Write the Formal Symbols for these atoms:
mercury, chlorine, and copper
201
80
Hg
35
17
Cl
64
29
Cu
Electrons don’t just fly around
willy nilly
(I like that expression, and it fits)
Electrons live in orbitals, which are also energy levels.
The closer to the nucleus, the lower the energy level the orbital is.
The orbitals are only so big, they fit certain numbers of electrons.
n = 1 (the first orbital) fits up to 2 electrons total
n = 2 (the second orbital) fits up to 8 electrons total
n = 3 (the third orbital) fits up to 8 electrons too, (sometimes up to 18)
Etc. More to come on this.
Let’s look at the periodic table now
Find silver, how many electrons does it have?
Find scandium, what is the electron configuration
and total number of electrons?
Find sulfur, what’s the configuration, and total
number of electrons?
Find oxygen, configuration and total?
Let’s look at the periodic table now
Find silver, how many electrons does it have? 47
Find scandium, what is the electron configuration
and total number of electrons? 21, 2-8-9-2
Find sulfur, what’s the configuration, and total
number of electrons? 16, 2-8-6
Find oxygen, configuration and total? 8, 2-6
For any atom, the atomic number is the number of
protons, and also the number of electrons.
The electron configuration always adds up to the atomic
number.
Examples:
Na #11 has a 2-8-1
or 2 + 8 + 1 = 11 total e―
C #6 has a 2-4 configuration or 2 + 4 = 6 total e―
K #19 has a 2-8-8-1 configuration
or 2 + 8 + 8 + 1 = 19 total e―