Chapter 9: Covalent Bonding and Molecules

Covalent bonds

Sharing of electrons, two atoms share electrons

Octet rule

Atoms are stabilized by having 8 electrons in the valence shell

Lewis structure

Shows the arrangement of covalently bonded atoms

Lone pairs

Two dots beside each other representing nonbonding pairs of electrons

Covalent Double and Triple Bonds

Double bonds have two dashes representing 4 shared electrons, triple bonds have three dashes representing 6 shared electrons

Drawing Lewis Structures

Step 1:Find the total amount of electrons, Step 2:Draw the base, Step 3:Fill the octets of the outer atoms, Step 4:Fill the octet of the central atom

Polyatomic ions

Groups of atoms with an overall charge

Formal charges

Estimates of the total electron charge around bonded atoms, assuming two atoms share electrons

Resonance Structures

Set of structures that show how electrons are distributed around a molecule or ion, used when a single Lewis structure is insufficient

Electronic geometry

Arrangement of electrons around the central atom

Molecular geometry

Shape caused by the arrangement of atoms, considers nonbonding and bonding pairs

Linear

Electronic geometry and molecular geometry for two electron groups

Trigonal Planar

Electronic geometry and molecular geometry for three electron groups

Tetrahedral

Electronic geometry and molecular geometry for four electron groups

Bent

Molecular geometry for three electron groups and one lone pair

Trigonal Pyramidal

Molecular geometry for four electron groups and one lone pair

Polar covalent bond

Atoms do not share electrons evenly

Electronegativity

How strongly electrons in bonded systems are "pulled", increases from left to right and decreases from top to bottom on the periodic table

Comparing Covalent, Polar Covalent, and Ionic Bonds

Calculating the difference in atom electronegativity to determine the type of bond

Molecular dipole

Overall polarity in a molecule, the molecule as a whole is polar and has a net dipole

Polar bonds

If a net dipole is present, the molecule is polar; if there is no net dipole, the molecule is non-polar.