Drawing Lewis Structures Worksheet

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Chem 231: Review Sheet for Chapter 1
Electronegativity (en): Ability of bonded atom to attract/pull electrons in bond toward itself.
1.
Increases in value as proceed across the periodic table within a row
from Group IA to Group VIIA. Note: Electronegativity of Group
VIIIA elements is zero.
2.
Decreases in value as proceed down the periodic table within a
column.
3.
In general:
non-metals –> high en –>
electronegative
metals –>
low en –>
electropositive
?
?
Difference in electronegativity (|
en|):
Value of |
en| gives information on type of bond
and compound present.
?
?
If |
en|
2.0
Ionic bonds are present between ions.
Ex. NaF (en: F=4.0; Na=0.9)
?
If |
en| = 0
Covalent bonds are present between atoms.
Ex. F
(en: F=4.0)
2
?
If 0 < |
en| < 2.0
Polar covalent bonds are present between
atoms. Ex. HCl (en: Cl=3.2; H=2.2)
Polar covalent bonds:
1.
Have a character intermediate between covalent and ionic
bonds.
2.
In a polar covalent bond, electron pairs are shared but not
equally. The electron pair spends more time near the more
electronegative atom giving this atom a partial negative
charge.
Formal Charge:
Charge on atom in given Lewis structure. A formal charge of +1 means
that the atom has one less valence e- surrounding it than the neutral atom.
A formal charge of -2 means that the atom has two more valence e-
surrounding it than the neutral atom.
To calculate: Formal Charge = (# Valence e-) - (# bonds) - (# nonbonding e-)

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