Download Periodic Trend- IE, EN, and AR 2015 Condensed and Updated

Periodic Trend­ IE, EN, and AR 2015 Condensed and Updated.notebook
December 18, 2015
Periodic Trends
Aim: To explain the trends of atomic radius,
ionization energy and electronegativity in terms of
nuclear charge and nuclear shielding.
Nov 15­3:07 PM
Definitions
Electronegativity: the attraction a nucleus has for valence electrons in a chemical bond.
Ionization energy: the amount of energy required to remove an atoms most loosely held electron (valence e­)
e-
e-
Atomic radius: the distance between the outer most principle energy level (valence shell) and the nucleus of an atom.
Nov 15­3:47 PM
1
Periodic Trend­ IE, EN, and AR 2015 Condensed and Updated.notebook
Definitions
December 18, 2015
= e-
Nuclear charge: The positive charge exerted by the protons in the nucleus of the atom. The greater the number of protons, the greater the nuclear charge.
Na
Nuclear shielding: Electrons outside of the nucleus shield it, blocking it's attractive force for the valence electrons.
Nov 16­8:57 AM
1. Electronegativity and ionization energy down a group
2. Atomic radius down a group
Li
Valence e-
EN=1.0
IE=520 kJ
AR=130.pm
+3
Valence e-
Na
+11
EN=0.9
IE= 496 kJ
AR=160.pm
Nuclear shielding: the shielding/blocking of a nucleus' attraction for valence e­ by PEL's surrounding it.
This increase in nuclear shielding weakens the hold a nucleus has for it's valence e­, lowering the EN and IE, making it easier to remove an e­.
Valence e-
K
1. Electronegativity and first ionization energy of an element decreases down a group because the # of PEL's increases, causing an increase in nuclear shielding.
+19
EN=0.8
IE=419 kJ
AR=200. pm
2. The atomic radius increases down a group because the number of occupied principle energy levels increases.
=electron
Nov 15­5:50 PM
2
Periodic Trend­ IE, EN, and AR 2015 Condensed and Updated.notebook
December 18, 2015
1. Electronegativity and ionization energy across a period.
2. Atomic radius across a period.
Li
Be
EN 1.0 1.6
IE (kJ) 520 ­­­­
AR (pm) 130. 99
+3
2­1
B
C
2.0 2.6
801 1086
84 75
N
O
F
3.0
­­­­­ 71 3.4
1314
64
4.0
1681
62
+9
+6
2­4
2­7
1. The electronegativity and ionization energy of an element increases across a period because of an increase in nuclear charge.(# of protons)
An increase in nuclear charge causes there to be a stronger hold on e­, strengthening the EN and increasing IE.
2. The atomic radius decreases across a period because the # of principle energy levels remains the same but the increased nuclear charge pulls the electron shells in closer.
Nov 16­8:36 PM
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