Download Class Notes - Electron Configuration

Bohr model of the atom
• Danish physicist Neils Bohr
proposed the concept of energy
levels to explain the spectrum of
hydrogen.
• He proposed that there are many
different energy levels that an
electron can be in around the
nucleus.
• These energy levels surround the
nucleus and are far away from the
nucleus (~10,000 times the
diameter of the nucleus).
Energy levels
• In the Bohr model of the
atom, the first energy level
can accept up to two
electrons.
• The second and third
energy levels hold up to
eight electrons each.
• The fourth and fifth energy
levels hold 18 electrons.
• 2,8,8,18…
Rules for Filling Energy Levels
When part of an atom, electrons always obey these rules:
1.
The energy of an electron must match one of the energy
levels in the atom.
2. Each energy level can hold only a certain number of
electrons, and no more, but it can hold less.
3. 2, 8, 8, 18
4. As electrons are added to an atom, they settle into the
lowest unfilled energy level.
5. Once an energy level is filled, then electrons start filling
the next energy level.
Practice
A. What is the highest energy level that contains electrons in the
neutral Oxygen atom?
B. How many electrons are in this highest energy level?
Solution:
Atomic # = 8
#Protons = 8
# Electrons = 8
Fill the energy levels:
A) 2nd Energy Level
B) 6 electrons.
Practice
A. What is the highest energy level that contains electrons in the
neutral Chlorine atom?
B. How many electrons are in this highest energy level?
Solution:
Atomic # = 17
#Protons = 17
# Electrons = 17
Fill the energy levels:
A) 3rd Energy Level
B) 7 electrons.