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An in-depth analysis of periodic trends in atomic size, ionization energy, and electronegativity. It covers the factors influencing atomic size, the shielding effect, group trends, period trends, and exceptions. The document also explains the concepts of electron affinity, ionic size, and the configuration of ions.
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GHS Honors Chem
GHS Honors Chem
� First problem: Where do you start
measuring from?
� The electron cloud doesn’t have a
definite edge.
� They get around this by measuring more than 1 atom at a time.
GHS Honors Chem
Radius
GHS Honors Chem
GHS Honors Chem
� The electron on the outermost energy level has to look through all the other energy levels to see the nucleus.
� Second electron has same shielding, if it is in the same period
� Shielding Increases down a Group, and is Constant across a Period. � Shielding Across a Period is Constant, but the EFFECTIVE NUCLEAR CHARGE INCREASES.
GHS Honors Chem
� As we go down a group... � each atom has another energy level, � so the atoms get bigger. � Shielding increases as well, so the nucleus has less of a hold on e -^ … distance is longer. � The Increased size of the Energy Levels down a group outweighs the increased nuclear charge
H Li
Na
K
Rb
GHS Honors Chem
Periodic Trends in Atomic Size
Na Mg Al Si P S Cl Ar GHS Honors Chem
Atomic Radius
Overall
GHS Honors Chem
Trends in Ionization Energy
� The amount of energy required to
completely remove an electron from a gaseous atom.
� Removing one electron makes a 1+
ion.
� The energy required to remove the
first electron is called the first ionization energy.
GHS Honors Chem
Ionization Energy
� The second IE is the energy required to remove the second electron.
� Always greater than first IE.
� The third IE is the energy required to remove a third electron.
� Greater than 1st or 2nd IE.
GHS Honors Chem
He Li Be B C N O F Ne
1A 2A 3A
GHS Honors Chem
GHS Honors Chem
Trends in Electron Affinity
GHS Honors Chem
Electron Affinity in the Periodic Table
GHS Honors Chem
Trends in Ionic Size
� Cations form by losing electrons.
� Cations are smaller that the atom they come from.
� Metals form cations.
� Cations of representative elements have noble gas configuration.
GHS Honors Chem
� Anions form by gaining electrons.
� Anions are bigger that the atom they come from.
� Nonmetals form anions.
� Anions of representative elements
have noble gas configuration.
Trends in Ionic Size
GHS Honors Chem
Revisiting Configuration of Ions
� Ions always have noble gas
configuration.
� Na is: 1s^2 2s^2 2p 6 3s^1
� Forms a 1+ ion: 1s^2 2s^2 2p 6
� Same configuration as Neon.
� Metals form ions with the
configuration of the noble gas before them - they lose electrons.
GHS Honors Chem
� Non-metals form ions by gaining
electrons to achieve noble gas configuration.
� They end up with the configuration of the noble gas after them.
Revisiting Configuration of Ions
GHS Honors Chem
Group Trends
Li 1+ Na1+ K1+
Rb 1+
Cs1+
GHS Honors Chem
Periodic Trends
� Across the period, nuclear charge increases so they get smaller.
� Energy level changes between anions and cations.
Li 1+
Be2+
B3+
C 4+
N 3- O2-^ F 1-
GHS Honors Chem
Size of Isoelectronic ions
� Iso- means the same
� Iso electronic ions have the same #
of electrons
� Al 3+^ Mg2+^ Na 1+^ Ne F 1-^ O 2-^ and N 3-^ all
have 10 electrons
� all have the configuration:
1s^2 2s^2 2p 6
GHS Honors Chem
Size of Isoelectronic ions
Al 3+
Mg 2+
Na1+^
Ne F^
1- O
2- N^
GHS Honors Chem
Electronegativity
GHS Honors Chem
Electronegativity Group Trend