Intramolecular Bonds and Chemical Reactions

What are chemical reactions?
Making and breaking of chemical bonds
What is bond energy?
Amount of energy required to break a bond. Used only for gaseous species.
What are the three types of intramolecular bonds?
1. Ionic Bonds
2. Covalent Bonds
3. Polar Covalent Bonds
Define ionic bonding. How is the energy of interaction calculated?
Electrostatic interactions between oppositely charged ions. Typically involves a metal and a nonmetal. Energy of interaction is calculated with Coloumb’s law.
Define lattice energy.
Change in energy when gaseous ions are combined to form 1 mol of an ionic solid
What is electron affinity?
A measurement of the change in energy when an electron is added to a neutral gas atom
What is ionization energy?
A measurement of the amount of energy needed to remove an electron from a neutral gas atom.
What is electron shielding?
A description of the ability of an atom’s inner electrons to shield the positively-charged nucleus from the valence electrons.
What is sublimation?
Process of going from a solid to a gas state.
What does it mean when we say that energy is a “state function?”
This refers to the fact that the change in energy in a reaction is path independent and that energy is conserved. Energy is a property.
What are four examples of ways in which we study bonds?
1. Physical properties
2. Solubility characteristics
3. Bond energy
4. Spectroscopy
Define bond length.
Distance between atoms at which the system has minimum energy.
What are covalent bonds?
When electrons are shared equally between atoms
What are polar covalent bonds?
When electrons are unequally shared between atoms
What is an essential characteristic of polar covalent bonds?
The resulting molecule typically has a dipole moment.
How are dipole moments (µ) measured? What happens if µ=0? If µ?0?
µ=Q*r, where Q is a charge and r and µ can be measured experimentally. µ is measured in Debye. If µ=0, then the molecule is non-polar, and if µ?0, then the molecule is polar.
Why don’t all molecules with polar bonds have a dipole moment?
Lone electron pairs and molecular structure affect dipole moment (ie. a linear arrangement cancels the dipole moment).
Ionic character increases as ________ increases.
Percent ionic character of a bond
(Measured dipole moment)/(Calculated dipole moment) x 100
What is the average energy of a single covalent bond?
300-400 kJ/mol