1. Electrons In Atoms
Chapter 5

2. Atomic Models Plum Pudding Model Nuclear Model Developed by JJ Thomson
Atom is made of positive material with electrons sitting in this positive material
Nuclear Model
Developed by Ernest Rutherford
Atom has a positive nucleus with electrons moving around it --- rest of the atom is empty space
Could not explain why metals or compounds of metals give off characteristic colors when heated in a flame
Could not explain the chemical properties of elements

3. Bohr Model Developed by Niels Bohr
Considered the simplest atom (hydrogen)—has one electron
Electron is found only in specific circular paths, or orbits, around the nucleus
Each electron orbit has a fixed energy
These fixed energies are called energy levels
An electron can jump from one energy level to another
Must gain or lose the right amount of energy
Amount of energy required to move an electron from one energy level to another energy level is known as a quantum of energy
Electrons cannot be between energy levels
The higher an electron is on the energy level, the farther it is from the nucleus

4. The energy levels are not equally spaced
Higher energy levels are closer together
The higher the energy level the less energy it takes to move from that energy level to another energy level
Problem with Bohr Model:
It failed in many ways to explain the energies absorbed and emitted by atoms with more than one electron

5. Quantum Mechanical Model
Developed by Erwin Schrödinger
Modern description of electrons in atoms that comes from the mathematical solutions to the Schrödinger equation
restricts the energy of the electrons, but the electrons do not have an exact path around the nucleus
Determines the allowed energies an electron can have and how likely it is to find the electron in various locations around the nucleus
The probability of finding an electron within a certain volume of space surrounding the nucleus can be represented as a fuzzy cloud
Cloud is more dense in areas where the probability of finding the electron is high

6. Atomic Orbitals
A region of space in which there is a high probability of finding an electron
Electrons can exist in several discrete principal energy levels
Each is designated by the principal quantum number(n) that are integers (1, 2, 3, 4, etc)
Each principal energy level consists of energy sublevels that have slightly different energy values
Designated by the letters s, p, d, and f
The principal quantum number will tell you the number of sublevels in that particular energy level
Ex: n=1 1st energy level has 1 sublevel

7. All orbitals in the same sublevel have equal energy
Each sublevel contains one or more orbitals, each of which can hold two electrons
s sublevel has one orbital
p sublevel has 3 orbitals
d sublevel has 5 orbitals
f sublevel has 7 orbitals
All orbitals in the same sublevel have equal energy
Each orbital also has a specific shape
s orbital is spherical

8. p orbitals have this shape
d orbitals have this shape

9. f orbitals have this shape

10. To determine how many orbitals each energy level contains use the equation n2
Remember: n = energy level
To determine how many electrons each energy level will hold use the equation 2n2