chapter 13: electrons in atoms models of the atom electron arrangement in atoms

Chapter 13: Electrons in Atoms

• Models of the Atom• Electron Arrangement in Atoms

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

Chapter 13: Electrons in Atoms-- Models of the Atom --

Dalton’s Model

• Solid indivisible mass• No concept of subatomic particles

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

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

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)

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”

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

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 33s (1 orbital), 3p (3 orbitals),

3d (5 orbitals)

n = 4 44s (1 orbital), 4p (3 orbitals),4d (5 orbitals), 4f (7 orbitals)

Chapter 13: Electrons in Atoms-- Models of the Atom --

Atomic Orbitals

• In the p orbitals, the areas close to the nucleus that have very little probability of finding an electron are called nodes

s orbital

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

Chapter 13: Electrons in Atoms-- Models of the Atom --

Atomic Orbitals

Increasing Energy(increasing distance from

nucleus)

Energy Level (n) 1 2 3 4

Maximum # of electrons allowed

2 8 18 32

**The maximum number of electrons that can occupy a principle energy level is given by the formula 2n2