Download The Atom & the Electron Configurtation

Unit 4: The Atom & the
Electron Configurtation
James Hutchison
The Atom & the Electron Configurtation
• Atomic orbitals
• The regions in which electrons are likely to be
found
• Principle Quantum numbers (n)
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Refers to a major energy level in an atom
These principle energy levels are assigned values in
order of increasing energy (n=1, n=2, n=3, and so on)
• The principal energy levels have a specific number
of sublevels
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The sublevels are designated by the principle energy
number and s, p, d, or f
Sublevels have specific numbers of orbitals
The maximum number of electrons that can occupy a
principle energy level is given by the formula 2n2,
where (n) is the principle quantum number.
− EX. Energy level n=3: 2(32) = 2(9) = 18 electrons
The Atom & the Electron Configurtation
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Atomic orbitals (cont)
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Atomic Orbitals are denoted by the letters s, p, d &
f (from inner to outer)
Atomic orbital shapes:
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s = spherical (there is 1 orbital)
p = dumbbell-shaped (there are 3 orbitals)
d = clover-leaf (there are 5 orbitals, but only 4 of the 5
are this shape)
f = too complicated to describe. (there are 7 orbitals)
The number and kinds of atomic orbitals depends
on the energy sublevel
Nodes are areas where the probability of finding
electrons is low
The Atom & the Electron
Configurtation
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Atomic orbitals (cont)
S→
←p
http://www.uky.edu/~holler/html/orbitals_2.html
The Atom & the Electron
Configurtation
• Electron Configurations
• The ways in which electrons are arranged
around the nucleus of an atom
• Three rules explain how to find the electron
configuration of atoms
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• Aufbau principle – e enter the lowest energy level
first
• Pauli exclusion principle – an atomic orbital may
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hold at most 2 e . They must have opposite spins.
− A vertical arrow indicates an electron and direction of
spin (↑ or ↓).
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• Hund’s rule – when e occupy orbitals of equal
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energy, one e enters each orbital until all the
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orbitals contain one e with parallel spins
The Atom & the Electron
Configurtation
• Shorthand Electron configurations:
• a. Involves writing the energy level and the symbol
for every sublevel occupied by an electron. (EX. 1s)
• b. A superscript number indicates the number of
electrons occupying that sublevel. (EX. 1s1)
• Aufbau Diagram – the diagonal rule
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