Download - Electron Arrangement
Rutherford’s Failure
Rutherford’s model could not describe behavior of atoms
Think About It: Why do
certain atoms react while others don’t? Why
do some fireworks
glow red and others green?
Bohr’s Atom
Hypothesis: each electron exists in a certain “orbit” or “energy level”
Electrons can never exist in between
Higher energy levels are further from the nucleus
Quanta
A quantum (pl. quanta) is the amount of energy required for an electron to move up an energy level
Quantum Mechanical Model
Determines allowed electron energies and how likely it is to find an electron in various locations around the nucleus
Dense cloud = high probability
Atomic Orbitals
Region of space in which there is a high probability of finding an electron
Why It’s Important:
The exact location of each electron
controls the atom’s properties!
“Address” of Electron
Each electron will be foundOn a PRINCIPAL ENERGY LEVEL In one of several SUBLEVELSOn an ORBITAL
Principal Quantum Numbers
Each principal energy level is assigned a principal quantum energy number, n
n can be 1, 2, 3, or 4, etc…
Sublevels
Each principal energy level has specific sublevels where an electron can be found
# of sublevels corresponds to principal quantum number Level 1 has 1 sublevel Level 2 has 2 sublevels…
Why s, p,d, and f?
The orbital names (s, p, d, f, g, h,...) are derived from the characteristics of their spectroscopic lines: sharp, principal, diffuse and fundamental, the rest being named in alphabetical order. For mnemonic reasons, some call them spherical & peripheral.
Atomic Orbitals
Each orbital can hold one pair of electrons
Each member of the pair has an opposite spin
2nd Principal Energy Level
• 2 sublevels (s and p)
• 2 electrons in s orbital• 6 electrons in p orbitals
• 8 total (10 combined with 1st)
3rd Principal Energy Level
• 3 sublevels (s, p and d)
• 2 electrons in s orbital• 6 electrons in p orbitals• 10 electrons in d orbitals
• 18 total (28 combined with 1st and 2nd)
4th Principal Energy Level
• 4 sublevels (s, p, d and f)
• 2 electrons in s orbital• 6 electrons in p orbitals• 10 electrons in d orbitals• 14 electrons in f orbitals
• 32 total (60 combined with 1st, 2nd, and 3rd)
Electron Configuration
Way that electrons are arranged in various orbitals
Arrangement governed by three rules
Aufbau Principle
Electrons first occupy sublevels/orbitals of lowest energy
Sublevels from some principal energy levels overlap others
Aufbau Diagrams
Display the order in which sublevels/orbitals are filled (to achieve the most stable configuration)
Pauli Exclusion Principle
Each orbital holds, at most, two electrons.
Two occupy the same orbital, two electrons must have opposite spins.
This is written or
Hund’s Rule
In each sublevel, one electron enters each orbital until each has one with the same spin direction
Not until all orbitals have one electron can any have two
Electron Configurations
Sublevels are filled in the following order:
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s
Electron Configurations
Contain 3 items:Number represents energy levelLetter represents sublevelSuperscript represents number of electrons
1s2
Electron Configurationsof Specific Elements
In a neutral element, the number of electrons is equal to the number of protons.