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Level 160

Electron Configurations & Periodic Trends


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Spin
Meaning of ms
+1/2 or -1/2
Possible values for ms
Ground state configuration
Lowest possible energy distribution
excited state
A state in which an atom has a higher potential energy than it has in its ground state
Aufbau principle
a subshell is completely filled before electrons are placed in the next higher subshell; exceptions: Cr, Cu
valence electrons
an electron in the highest occupied energy level of an atom;available to be lost, gained, or shared in the formation of chemical compounds
Size
Larger size means a stronger acid
Shape
Meaning of l
Electron-to-electron repulsion
What causes different subshells to be different energies?
When writing electron configurations for cations (+)
Remove electrons from the highest value of n first
Hund's Rule
- electrons occupy equal energy orbitals so as to maximize the number of unpaired e-
Diamagnetic
A substance that is not attracted to a magnetic field
Paramagnetic
A substance that is attracted to a magnetic field
When is a substance paramagnetic?
Have 1 or more unpaired electrons
Noble gases
Elements in group 8A of the periodic table. Have no charge and are gases under normal conditions. (Helium, Neon, Argon, Krypton, Xenon, Radon)
Core electrons
Inner electrons occupying principle quantum numbers that have full s & p orbitals.Inaccessible to chemical reagents
Less electron-electron repulsion
Why does chromium have one electron in every subshell?
Special stability with a completely full subshell
Why does copper have 1 half filled subshell?
Cation
(+) Lose an electron
Anion
(-) Gain an electron
Isoelectronic
Atoms having the same electronic configuration
s, d
When a cation is formed from an atom of a transition metal, electrons are always removed first form the orbital and then the orbitals
Effective nuclear charge (Zeff)
The "positive charge" actually "felt" by an electron
Equation fo Zeff
Zeff=Z-number of inner or core electrons
Decreases
When an atom gains electrons, its oxidation number _______ and it is said to have been reduced.
As n increases, electron density decreases
Why does screening decrease as n increases?
Why does screening decrease as l increase?
The more organized orbital shapes puts electron density away from the nucleus
Larger and less stable
As principal quantum number n increases, the occupied outermost atomic orbitals become
Increases (electrons feel the nucleus more)
As you move across the periodic table, Zeff
Decreases from left to right
When comparing the size of a specific electron orbital across a row in the periodic table, size
increases
Bob the snowboarder speeds up while descending a hill with friction. He then flies off a cliff (we neglect air resistance). While BOB is descending the initial hill, what happens to his KE?
Why does atomic size decrease across a periodic table?
As Zeff increases, radius decreases. Nucleus has a greater pull on the electrons, bringing them in closer.
Smaller
Cations are always than their corresponding neutral atom
Why are cations smaller?
Reduced number of electrons decreases electron to electron repulsion
Larger
Anions are always than their corresponding neutral atom
Why are anions larger?
More electron to electron repulsion
Ionization Energy
Energy needed to remove an electron from the valence shell of an atom - how easily an atom can become an ion (COMPARE REACTIVITY OF A METAL)
Th
The higher the ionization energy
Electron Affinity
Energy emitted upon addition of an electron - tendency to gain an electron (COMPARE REACTIVITY OF A NONMETAL)
First ionization energy
Increases from left to right across each row and decreases from top to bottom of each column of the periodic table
As size increases
Ionization energy decreases
Half-filled subshell
Why is it easier to remove an electron from O than it is from N?
Higher
Electron affinity tends to become from left to right across a row of the periodic table
ml
Anywhere between + or - l
mn
+ or - 1/2 (can be either)