Transcript Bohr and Quantum Mechanical Model

A Whirlwind Introduction to
Bohr Model and Quantum
Mechanical Model
We’ve got a lot to do, so let’s get
going!!
Remember Niels Bohr?
• What was Bohr’s main contribution?
– Planetary model of the atom
– Electrons orbit the nucleus.
• Each orbit (also called shells) has a
specific amount of energy.
• Each orbit also has a maximum number of
electrons it can hold.
– Electrons must be in an orbit; they cannot be
in between.
How About Those Energy Levels?
• Orbits labeled with whole numbers,
n=1, n=2, n=3, etc.
• Closer to the Nucleus = Less Energy.
How Much Can an Orbit Hold?
Must fill up the lower-energy shells before moving outward.
How to Draw Bohr Models
1. Find number of electrons.
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For a neutral (no charge) atom,
atomic # = # protons = # electrons
2. Draw a nucleus in the middle.
3. Draw circles for electron shells.
4. Place dots on shells to represent
electrons.
What Would be the Bohr Model for Al?
1. Atomic # = ?
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13
# protons = ? 13
# electrons = ? 13
2. Maximum numbers to fill up shells
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Maximum # electrons in 1st shell? 2
– Do you have that many to put in there? yes
– If you fill up that shell, how may e- are left? 13-2=11
Maximum # electrons in 2nd shell? 8
– Do you have that many to put in there? yes
– If you fill up that shell, how may e- are left? 11-8 = 3
Maximum # electrons in 3rd shell? 18
– Do you have that many to put in there? no
– Can you leave the very outer one partly empty? yes
– So how many total will you put in the 3rd level? 3
3. Then draw it!
Isn’t It Pretty?
Notice e- are in pairs except for n=1. Not
necessary, but would be good to start practicing.
You Do One!
• You knew that was coming, didn’t you?
• Do Chlorine, Cl!
Check It!
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Cl: atomic number = 17 = 17p+ = 17e1st shell holds 2 (17-2 = 15 left)
2nd shell holds 8 (15-8 = 7 left)
3rd shell holds 18 (rest will fit in there)
Groupwork, Everybody’s Favorite!
1. Without leaving your seat, find a group of 3.
2. Slide your desks together gently.
3. ONE person from each group
needs to come get 1 piece
of paper and 1 marker.
4. Hold it portrait style.
5. Draw lines to make
three even sections.
6. Lay your heads down
when you’re done.
In each section…
Element Name, Symbol
1st shell = ___ electrons
2nd shell = ___ electrons
3rd shell = ___ electrons
Bohr
model
Now Homework…Yay!
• More practice with Bohr models!!
– Hydrogen, H
– Oxygen, O
– Helium, He
– Magnesium, Mg
• Don’t get excited; we’re not done!
Electron Movements
• Ground state: energy level an electron
usually occupies
• But it can move to a higher-energy, less
stable level, called an excited state.
• After it’s done being excited, the electron
can release the energy and move back
down to ground state.
See?
I’ve Had Enough of Bohr…
• Bohr’s model worked great for H, but not
so great for the rest of the elements.
• Quantum Mechanical Model was
established and in use today!
Quantum Mechanical Model
• Like Bohr’s model, electrons exist in energy
levels (and not in between).
• Like Bohr, the levels are labeled as whole
numbers, from the inside to the outside.
• Like Bohr, the lower n, the lower energy.
• Unlike Bohr, this model has electron clouds
(also called orbitals) instead of orbits which
show where an electron is likely to be.
Sounds Fascinating, Right?!
• It is!!
• The different electron clouds have different
shapes, and there is a letter associated
with each!
• Get excited!!
s orbital
• Spherical shape
• Can hold up to 2 e• Lowest energy
Color in s-block
Helium
belongs with
the s-block!
p orbital
• Dumb-bell shaped
• Can hold up to 6 e• More energy than s
orbital
Color in p-block
Helium
belongs with
the s-block!
d orbital
• Different shapes.
• Can hold up to 10 e• More energy than p
orbital.
Color in d-block
f orbital
• Very odd shapes
• Can hold up to 14 e• Highest energy
Color in f-block:
Make them
the same
color…
Now let’s go practice with the
shapes.
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Partners.
Lab tables.
Aprons, no goggles.
1 group per bowl.
Put your hands on your head when you
get there and are ready to go.
Instructions:
• In your bowl, add:
– 1/4 cup of flour (1 scoop)
– 2 tablespoons of salt (2 scoops)
– 29 mL of water
• Mix well, with a spatula or your hands.
• You may make school-appropriate shapes
until everyone catches up.