Bonding: Ionic, Covalent, Lewis Structures Flashcards
What is the Lewis theory of bonding?
- Atoms form chemical bonds to achieve a stable octet of electrons.
- Exchange of electrons between metal and non-metal atoms is an ionic bond.
- Sharing of electrons between atoms of non-metals is a covalent bond.
What are the 5 steps for drawing a Lewis diagram?
- Central atom is the least electronegative.
- Total number of valence electrons. (cations subtract, anions add)
- Bond central atom to surrounding atoms.
- Add lone pairs to surrounding atoms, then central atoms.
- Move lone pairs from surrounding atoms to form a double or triple bond, so that central atom has a complete octet.
What do hydrogens usually bond to?
Oxygen
Where do the exceptions to the octet rule end? (for having less than 8 electrons).
Carbon
Where do the exceptions to the octet rule begin? (for having more than 8 electrons).
If an element in 3+ row is the central atom.
Why can certain elements have more than 8 electrons in their valence shell?
They have unfilled d-orbitals which can be used in bonding.
What can happen to the valence electrons if there is enough energy?
They absorb energy, become excited, and move up into the 3d subshell. They each occupy their own orbital.
With enough energy, what could happen to S (3s2, 3p4)?
Become 3s1, 3p3, 3d2.
When do you use formal charge?
When there are two different ways to write the molecule which both look fine.
What is formal charge?
The difference in the number of valence electrons in the atom and the number of valence electrons in the Lewis structure.
What is the formula for formal charge?
FC= (Group #) - (# of covalent bonds) - (#of electrons in lone pairs)
How do you use formal charge?
Using the formula, check the FC on the atoms in all possible structures.
What will the correct lewis structure will have?
- All formal charges as close to zero as possible.
2. Negative formal charges on electronegative atoms (halogens or oxygen).
