Chemistry Test - Bonding Part II Flashcards
Valence Electron:
An electron in the outermost energy level or orbit.
Electronegativity:
The ability of an atom to attract bonding electrons to itself.
Covalent Bond:
The bond that results from the sharing of a pair of electrons by two atoms.
Polar Covalent Bond:
A covalent bond formed between atoms with significantly different electronegativities resulting in a bond with localized positive and negative charges or poles.
Ionic Bond:
The electrostatic force of attraction between a positive ion and a negative; a type of chemical bond.
Covalent Range
0 to 0.4
For example CH4
C 2.6
H -2.2
= 0.4
Charges: none
Polar or non-polar: non polar covalent
Polar Covalent Range
0.5 to 1.7
For example H20
O 3.4
H -2.2
= 1.2
Bond Type: polar covalent
Charges: partial
Ionic Range
1.8+
For example LiF
F 4.0
Li -1.0
=3.0
Bond TYpe: Ionic
Full charges
In a polar covalent bond or ionic bond which atom is labelled with a negative symbol?
The one with the higher electronegativity.
What symbol do you use to draw a bond dipole?
Delta δ+ δ- and that arrow thing.
Lesson #18 - VSEPR Shapes and Polarity
Steps to drawing:
- Calculate the electronegativity difference
- Identify the bond rating (polar-covalent bond)
- Identify the charge type (partial charges)
- Draw the diagram according to how many of the second molecule, add in the deltas and the dipole
Identify as polar, non-polar, or non-polar with dipoles that cancel out
Ion - Ion
Strongest force of attraction (actually an ionic bond!). Occurs between 2 Ionic Molecules with opposite charges (+1 - 1-) Examples (NaCl, NaBr, KCl, etc).
Ion - Dipole
Second Strongest force of attraction. Medium strength. A polar ion and a molecule are attracted to each other. (Like the positive end of a polar water molecule being attracted to salt). (δ+ - 1-)
Hydrogen Bonding
Medium strength force of attraction between two dipoles but slightly stronger than dipole-dipole. “Hydrogen Almost Bond.” It happens when F, O, or N atoms are bonded to an H (i.e. HF, H20, or NH3).
Dipole-Dipole
A weaker Dipole-Dipole source, the electronegativity difference is smaller, Between covalent polar molecules without an F, O, or N attached to an H. (δ+ - δ-)
London Dispersion Forces
The weakest force occurs between non-polar, no charges, molecules. (C-H, C-C)
Order of forces from strongest to weakest:
- Ion-Ion Bond
- Ion-Dipole Force
- Hydrogen Bonding Force
- Dipole-Dipole Force
- London Dispersion Forces
If…
Both particles are ions with full +1, +2, +3 or -1, -2, -3 charge then its…
Ion-Ion
If…
One of the particles is a fully charged ion and one is a polar covalent molecule it’s…
Ion-Dipole
If…
Both molecules have an H attached to an O,F, or N it’s…
Hydrogen Bonding
To distinguish between LDF and Dipole-Dipole?
calculate electronegativity if it’s between 0-0.4 it’s LDF, anything higher is Dipole-Dipole
Bigger Dots =
Bigger Force so draw Ion-Ion with the biggest dots and LDF with the smallest (Ion-Ion should really be a line)
Dots go from positive to negatice:
ions have the charge
O, F, and N are always the negatives, H will be the positive
Melting Points and Structure Format - Wax
Wax has non-polar covalent CC and CH bonds with no charges. Therefore, Wax is a non-polar compound with weak LDF forces sticking the molecules to each other. Therefore, little heat is needed to separate the molecules from each other and wax melts first.
Melting Points and Structure Format - Sugar
Sugar has polar covalent COH bonds with partial charges. Therefore, Sugar is a polar compound with Upper Medium H-Bond forces sticking the molecules to each other. Therefore, a medium amount of heat is needed to separate the molecules from each other and it melts 2nd.
Melting Points and Structure Format - Salt
Salt has ionic NaCl bonds with full charges. Therefore, Salt is an ionic compound with ionic super strong ion-ion forces (bond) sticking the molecules to each other. Therefore, a lot of heat is needed to separate the molecules and it melts 3rd.