Flashcards in General Chemistry Chapter 3: Bonding and Chemical Interaction Deck (22)
What does the octet rule state?
elements will be most stable with eight valence electrons
What are exceptions to the octet rule?
- Elements with an incomplete octet are stable with fewer than eight electrons and include H, He, Li, Be and B
- Elements with an expanded octet are stable with more than eight electrons (period 3 or greater)
- Compounds with an odd number of electrons cannot have eight electrons on each element.
What is an ionic bond?
formed via the transfer of 1 or more electrons from an element with a relatively low ionization energy to an element with a relatively high electron affinity.
What types of elements generally form ionic bonds?
Generally forms between metals and nonmetals
What is a positively charged ion called? Negatively?
+ = cation
- = anion
What doe ionic compound form? (structure)
Crystalline lattice - large organized arrays of ions
What are special properties of ionic compounds?
tend to dissociate in water and other polar substances
tend to have high melting points
What is a covalent bond?
sharing of electrons between elements of similar electronegativities
What is a bond order?
Refers to whether a covalent bond is a single bond, double bond or triple bond. As bond order increases, bond strength increases, bond energy increases and bond length decreases.
When are covalent bonds considered nonpolar?
when there is either no difference or a small difference in electronegativity between the atoms (
When are covalent bonds considered polar?
when there is a significant difference in electronegativity (0.5 to 1.7), but not quite to the extent that would be seen in an ionic bond.
What are coordinate covalent bonds?
a single atom provides both bonding electrons while the other atom does not contribute any; coordinate covalent bonds are most often found in Lewis acid-base chemistry .
When do formal charges exist?
When an atom is surrounded by more or fewer valence electrons than it has in its neutral state.
What are resonance structures?
differences in configurations/distribution of electrons
What is the valence shell electron pair repulsion theory?
predicts the 3D molecular geometry of covalently bonded molecules. In this theory, electrons arrange themselves as far apart as they can.
Which results in more repulsion? Bonding or non-bonding electrons?
What are sigma bonds?
the result of head-to-head overlap
What are pi bonds?
the result of overlap of two parallel electron cloud densities.
What are three types of intermolecular forces?
electrostatic attractions between molecules. They are significantly weaker than covalent bonds.
What are london dispersion forces?
interaction in all atoms and molecules that increases as size increases
What are dipole-dipole interactions?
occur between the oppositely charged ends of polar molecules, stronger than London, interactions are evident in the solid and liquid, negligible in gas