Download Electron Configurations (Section 5.3) part 1

Electron
Configurations
Objectives:
3.0 Use the periodic table to identify
periodic trends, including atomic radii,
ionization energy, electronegativity, and
energy levels.
3.1 Utilizing electron configurations,
Lewis dot structures, and orbital
notations to write chemical formulas
Ground State Electron
Configurations
• Electron configuration: the arrangement
of electrons in an atom
• What is “ground state”?
• Three rules define how electrons are
arranged in an atom’s orbitals:
1. The aufbau principle
2. The Pauli exclusion principle
3. Hund’s rule
The Aufbau Principle
• Each electron occupies the lowest energy
orbital available, according to the aufbau
diagram:
The Pauli Exclusion Principle
• A maximum of 2 electrons may occupy a
single atomic orbital, but ONLY if the
electrons have opposite spins
(represented by ↑ and ↓).
Hund’s Rule
• Single electrons with the same spin must
occupy each equal-energy orbital before
additional electrons with opposite spins
can occupy the same orbitals (i.e., 1 ↑ in
each 3p orbital BEFORE a ↓ can pair up
with a ↑ in an orbital).
Orbital Diagrams and Electron
Configuration Notations
• These are just 2 different ways to
represent an atom’s electron
configuration.
Orbital Diagrams:
• Have a box for each of the atom’s orbitals.
• Boxes contain either ↑ (1 electron), or ↑↓
(full orbital), or may be empty.
• Each box is labeled with the principal
quantum number and the sublevel
associated with the orbital.
• Examples on board
Electron Configuration
Notation
• Shorthand to designate all electrons and
their orbitals
• Designates principal energy level and
sublevel, and includes a superscript to
show the number of electrons in the
orbital.
• Example: Carbon 1s22s22p2
• What is the electron diagram for carbon?
• Table 5-3, p.137
Electron Configuration
Notation (cont.)
• What is the electron configuration
notation for the following elements?
a.
b.
c.
d.
e.
f.
Helium
Neon
Argon
Krypton
Xenon
Radon
• What do these elements have in
common?
Electron Configuration
Notation (cont.)
• Electron configuration notation can be
abbreviated by noble-gas notation.
• [He] = 1s2
• [Ne] = 1s22s22p6
• So magnesium can be written:
– 1s22s22p63s2 -OR– [Ne]3s2
• How would you write phosphorous?