The Atom Tutorial
Chemistry
Atoms are named according to their number of protons Add a proton it becomes BORON!
Atoms/Ions/Isotopes
Protons
Electrons Neutrons Anything with 6 protons is CARBON!
Symbol
8 4 Be 9 5 B 12 6 C
Mass # 8 9
# p+ 4 5
# no 4 5
# e4 5
12
6
5
6
Isotopes
More or less neutrons
Atoms/Ions/Isotopes
Protons
Electrons Neutrons
Add a neutron it is STILL Beryllium, just a different MASS!
Symbol
8 4 Be 9 5 Be
Mass # 8 9
# p+ 4 4
# no 4 5
# e4 4
Ions
More or less electrons
Atoms/Ions/Isotopes
Protons
Electrons Neutrons
Take away two electrons, charges don’t balance anymore it is an ion with a +2 charge!
Symbol
8 4 Be 8 Be+2 4
Mass # 8 8
# p+ 4 4
# no 4 4
# e4 2
Working with Symbolizing
I like using these symbols, you can see the subtraction problem you will need to do.
96 42 54
Mo
Z = 42 p+ = 42 n0 = 54 e- = 42
Working with Symbolizing
I like using these symbols, you can see the subtraction problem you will need to do.
25 12 13
Mg
+2
THINK of the charged particles 12 positive protons
Z = 12 p+ = 12 n0 = 13 e- = 10
So… you’ll only need 10 negative electrons to get a balance of +2 on a particle
Think About It!
• An atoms weight comes from the protons and neutrons. The electrons are so tiny they don’t matter for weight! • Like a sumo wrestler weighing in with ten lady bugs on his shoulder. (the electrons are like the lady bugs, they don’t change his mass very much).
Remember John Dalton’s Atom
• Dalton thought of atoms as indivisible spheres • His proof for this was the Law of Definite Composition (water is H2O not H1.5O)
• He of course was wrong… • Atoms can be split into parts • no p+ and e-
Models of the Atom
Person Model of Atom
Solid sphere
Evidence
Law of Definite Composition Cathode Ray Tube
Flaw
Can divide atoms
Dalton
Thomson Rutherford Bohr
Sphere with electrons
Electrons not moving
Electrons orbit a nucleus
Gold Foil Experiment
Not circular orbits
Orbitals of electrons
Line Spectra
Only worked for hydrogen
Electron Configurations
3 Simple Rules 1) Electrons fill lowest energy level first 2) Maximum number of 2 e- per orbital 3) Orbitals half-fill before they fill (per sublevel)
NOT (Each orbital gets one before an orbital can get seconds)
6p 6s 5s 4s 5p 4p
5d
4f
4d 3d
Ca = 20 e-
3s
3p
2s
2p
1s
1s2 2s2 2p6 3s2 3p6 4s2
6p 6s 5s 4s 5p 4p
5d
4f
4d 3d
Ca+2 = 18 e-
3s
3p
2s
2p
1s
1s2 2s2 2p6 3s2 3p6
Dot Diagrams
• Symbolize outer shell electrons (Highest s and p orbitals only) • Why?
Those are the electrons involved in bonding and chemical reactions
LEFT RIGHT TOP BOTTOM
X In the table in Assignment #4: Na 1s22s22p63s1 Ne 1s22s22p6
Na
Ne
Ni
1s22s22p63s23p64s23d8
Ni
Using the Periodic Table To Draw Dot Diagrams
Lab 20
Element and Electron Atomic Number Configuration
Highest s and p ONLY
Orbital Filling Diagram
Dot Diagram
nitrogen (7)
1s22s22p3
s
p
N
Average Atomic Mass (Atomic Weight)
• An average of an element’s isotopes • The number seen on the periodic table
How to Calculate Average Atomic Weight
Na is made up of: 95.6% Na-23
and
4.4% Na-22
{ (0.956) (23) + (0.044) (22) } =
(21.988 + 0.968) =
22.956 23.0 g/mol
Lab 19 Explanation
Nitrogen Oxygen CO2
~ 78% ~ 21% ~ 0.3%
Height of Water = the space the oxygen gas used to take up before it became a solid