Quantum Numbers Quantum Numbers specify the properties of atomic orbitals and their electrons There are four quantum numbers: principal quantum number orbital quantum number magnetic quantum number spin quantum number

Principal Quantum Number The principal quantum number (n) specifies the main energy levels around the nucleus As n increases, the distance from the nucleus increases (So as the numbers become larger the levels become further from the nucleus) Currently the values for n are 1 to 7 These orbitals are called subshells or sublevels The four most common Principal quantum numbers are given letter abbreviations s, p, d, f

Orbital Quantum Number Orbital Quantum Number ( l ) indicates the shape of the orbital where the electron can be found Begin 1st 2-13-2000

“s” Orbital

“p” Orbital

“d” Orbital

“f” Orbital

Magnetic Quantum Number 3. Magnetic Quantum Number (ml ): indicates the orientation of an orbital about the nucleus it tells which axis that sublevel is located on (x, y, or z axis)

Spin Quantum Number The Spin Quantum Number (s) is a value (of 1/2) that describes the angular momentum of an electron. An electron spins around an axis and has both angular momentum and orbital angular momentum. Because angular momentum is a vector, the Spin Quantum Number (s) has both a magnitude (1/2) and direction (+ or -)

Begin 3rd 2-15-2000 Using Quantum Numbers Quantum numbers can be used to write electron configurations Electron configurations show how electrons are most likely distributed around the nucleus Begin 3rd 2-15-2000

Rules for Electron Configurations 1. Aufbau Principle: Electrons enter orbitals of lowest energy first 2. Hund’s Rule: Orbitals of equal energy are each occupied by one electron before any one orbital is occupied by a second electron Begin 5th 2-15-2000

Rules for Electron Configurations 3. Pauli Exclusion Principle: an atomic orbital may describe at most two electrons The maximum number of electrons in any orbital is “2” No two electrons in the same atom can have the same set of four quantum numbers

Guidelines for Electron Configurations 1. Determine number of electrons 2. Each orbital can hold 2 electrons 3. A “ s ” sublevel has 1 orbital and holds 2 electrons A “ p ” sublevel has 3 orbitals and holds 6 electrons A “ d ” sublevel has 5 orbitals and holds 10 electrons A “ f ” sublevel has 7 orbitals and holds 14 electrons

Order of Filling of Energy Levels 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 6f 7s 7p 7d 7f Begin 7th 2-15-2000

Warm-Up The density of a substance is 5.25 g/mL. What is the mass(in kilograms) of 0.75 L of the substance?

Warm-Up What elements are the following: 1s22s22p4 1s22s22p63s23p64s23d7 1s22s22p63s23p64s23d104p65s24d105p11

Practice Long Hand Electron Configurations Cd B P Ba As I Na

Review Write the Long Hand/Expanded electron configuration for the following elements: Sn Ga Y

Noble Gas Electron Configuration Place the following Element using the Noble Gas/short hand electron configuration: Sc I Ru Fr Fe F

Practice Problems Write the Noble Gas Electron Configuration for the following: Tc Zn K I P

Orbital diagrams show how electrons fill each sublevel s has 1 sublevel p has 3 sublevels d has 5 sublevels f has 7 sublevels