Chapter 3 Flashcards
Which elements have an incomplete octet?
Hydrogen - 2 electrons Helium - 2 electrons Lithium- 2 electrons Beryllium- 4 electrons Boron- 6 electrons
Which elements have an expanded octet ?
Any element in period 3 or greater
How many electrons do P, S and Cl hold ?
10, 12, 14
What is a nonpolar covalent bond ?
Electrons are equally shared
What is a polar covalent bond ?
Electrons are shared unequally
Coordinate covalent
If both shared electrons are contributed by one of the two atoms
Cation
Metal lose electrons
Anion
Nonmetal gain electrons
What are the five characteristics of ionic bonds ?
- High melting and boiling point
- Highly soluble in water
- Good conductors of heat and electricity
- Large electronegativity difference between ions
- Crystal lattice arrangement as solids to maximize attraction
What are the characteristics of covalent bonds ?
- Lower melting and boiling point
- Don’t break down into ions
- Poor conductors of heat and electricity in
Iiquid or aqueous state
Bond order
Shared electron pairs between two atoms
Single bond- 1
Double bond - 2
Triple bond- 3
Bond energy
Energy required to break a bond
What electronegativity difference is generally considered non polar ?
0.5
What electronegativity difference is considered polar ?
0.5 to 1.7
What is the equation for dipole moment ?
p= qd
p = dipole moment
q=magnitude of charge
d= displacement vector that separates two charges
Lewis base
Donates a pair of electrons
Lewis acid
Accepts a pair of electrons
Formal charge formula
Formal charge = valence electrons - Nnonbonding - 1/2Nbonding
What is the criteria for Lewis structures ? Which Lewis structure is preferred ?
- Small or no formal charge
- Less separation between opposite charges
- Negative formal charges are placed on more electronegative atoms
What is the ideal bond angle for tetrahedral geometry ?
109.5 degrees
What are the three types of electrostatic interactions and rank them from strongest to weakest?
- Hydrogen bond
- Dipole- dipole interactions
- London dispersion forces
London dispersion forces
Short lived induced dipoles that extend over short distance. Larger molecules have greater dispersion forces
Dipole dipole interactions
Polar molecules orient themselves in a way in which the negative dipole interacts with positive
Last longer than London dispersion
Hydrogen bond
Strong dipole dipole interactions that are specific to hydrogen binding to fluorine , oxygen and nitrogen . They are intermolecular or intramolecular .
