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Electron ConfigurationsChemistry 1d - Students know how to use the periodic table to determine the number of electrons available
for bonding.
Review...How to identify an element: - Look at the protonsHow to find protons:- Look at the atomic numberHow to find neutrons:- Subtract atomic mass from atomic number (the #
of protons)How to find electrons in a neutral (no charge) atom :- Always equals the number of protons
• Atomic number tells us how many electrons an atom has in a neutral atom
• Valence electrons (the outermost e-) are known by looking at the elements’ family/group
The Periodic Table and Electrons
But how do we know where all
an element’s electrons are
found?
• Arrangement of the periodic table which tells us where each electron in an atom is located (which energy level and sublevel) and explains how electrons fill an atom
Electron Configurations
-Nucleus
Which Orbital do I go to?
Negative electron
Energy Levels• Rows/Periods = Energy
Levels (7 on PT)• Energy levels are divided
into sublevels (s, p, d, f)• Sublevels are divided into a
shape of space called orbitals
• Each orbital/shape can ONLY hold 2 electrons!
s, p, d, f Blocks• The periodic table can be divided into sections
called blocks (energy sublevels)• 4 blocks/sublevels = s, p, d, f• s, p, d, f sublevels are divided into orbitals• s = 1 shape • p = 3 shapes • d = 5 shapes • f = 7 shapes
s-BLOCK p-BLOCKd-BLOCK
f-BLOCK
How many electrons can fit in each Orbital?
Just Count the # of Elements in each
Block!
How many electrons are in each block?
• s-block = 2 electrons• p-block = 6 electrons• d-block = 10 electrons• f-block = 14 electrons
Just count the # of
elements in each block!
1. N = 1 (1st row/energy level): • Smallest energy level• Can only hold 2 electrons (2 = s-block)2. N = 2 (2nd row/energy level): • A little larger than the first• Can only hold 8 electrons (2 = s-block; 6 = p-
block)
How many electrons per energy level (row)?
3. N = 3 (3rd row/energy level): • A little larger than the second• Can hold 18 electrons (2 = s-Block; 6 = p-Block;
10 = d-Block)4. N = 4 (4th row/energy level): • Larger than the third energy level• Can hold 32 electrons5. N = 5 (5th row/energy level): • Larger than the fourth energy level• Can hold 50 electrons
6. N = 6 (6th row/energy level): • Larger than the 5th energy level• Can hold 72 electrons 7. N = 7 (7th row/energy level): • Largest energy level• Can hold 98 electrons
The rule for determining the number of electrons is 2(n2) The
number of energy levels in represented in N.
2n2
2(6)2
2(36) = 72
sp
d
f
1S2S3S4S5S6S7S
4F5F
3D4D5D6D
2P3P4P5P
6P7P
The S-Block always fills first!
D-Block ONE Row Behind!
F-Block TWO Rows Behind!
Steps for Finding Electron Confi gurati ons for an Element
1. Find the element. 2. List the energy levels, orbitals (blocks), and
number of electrons in each block as you make your way to the element that you are trying to find the configuration for.
Cerium 1s2 2s2p6 3s2p6d10 4s2p6d10f1 5s2p6d1 6s2
The 2s electrons have a higher energy than the 1selectrons. Therefore, the 2selectrons are generally moredistant from the nucleus,making the 2s orbital largerthan the 1s orbital.
so 3s electrons aregenerally foundfurther from thenucleus than 1s,2s, or 2p electrons