1. Chapter 13: Electrons in Atoms
Models of the Atom
Electron Arrangement in Atoms

2. Chapter 13: Electrons in Atoms -- Models of the Atom --
The Evolution of Atomic Models
Dalton Model
Thomson Model
Rutherford Model
Bohr Model
Quantum Mechanical Model

3. Chapter 13: Electrons in Atoms -- Models of the Atom --
Dalton’s Model
Solid indivisible mass
No concept of subatomic particles

4. Chapter 13: Electrons in Atoms -- Models of the Atom --
Thomson’s Model
The “plum-pudding” model
Electrons stuck in positively charged material
Nothing about protons, neutrons, arrangements, or ion formation

5. Chapter 13: Electrons in Atoms -- Models of the Atom --
Rutherford’s Model
The first nuclear atom
Most of the mass is concentrated in the nucleus of the atom

6. Chapter 13: Electrons in Atoms -- Models of the Atom --
Bohr’s model
Said electrons orbited nucleus in fixed definite paths
Each energy level has electrons that can “jump” (quantum jump) to other energy levels based on specific amounts of energy (quanta)

7. Chapter 13: Electrons in Atoms -- Models of the Atom --
The Quantum Mechanical Model
Mathematical solutions from Erwin Schrodinger’s model developed this
Estimation of probability of where electrons are found in the “fuzzy cloud”

8. Chapter 13: Electrons in Atoms -- Models of the Atom --
The Quantum Mechanical Model
Designates energy levels of electrons by using principal quantum numbers (n)
n = 1, 2, 3, 4, …
Average distance of the electron from the nucleus increases with increasing values of n
Sublevels of arrangement (arrangements in space)
Sublevel contains atomic orbitals (regions where electrons are most likely to be found)
Denoted by the letters s, p, d, and f
Each orbital contains two electrons

9. Chapter 13: Electrons in Atoms -- Models of the Atom --
The Quantum Mechanical Model
Summary of Principal Energy Levels, Sublevels, and Atomic Orbitals
Principal Energy Level
Number of sublevels
Type of sublevel
n = 1 1
1s (1 orbital)
n = 2 2
2s (1 orbital), 2p (3 orbitals)
n = 3 3
3s (1 orbital), 3p (3 orbitals),
3d (5 orbitals)
n = 4 4
4s (1 orbital), 4p (3 orbitals),
4d (5 orbitals), 4f (7 orbitals)

10. Chapter 13: Electrons in Atoms -- Models of the Atom --
Atomic Orbitals
s orbital
In the p orbitals, the areas close to the nucleus that have very little probability of finding an electron are called nodes

11. Chapter 13: Electrons in Atoms -- Models of the Atom --
Atomic Orbitals
In the d orbitals, the areas close to the nucleus that have very little probability of finding an electron are called nodes

12. Chapter 13: Electrons in Atoms -- Models of the Atom --
Atomic Orbitals
**The maximum number of electrons that can occupy a principle energy level is given by the formula 2n2
Increasing Energy
(increasing distance from nucleus)
Energy Level (n) 1 2 3 4
Maximum # of electrons allowed 8 18 32