Electron Dot Structures - Helpful tools in thinking about bonding.
Pictorial representation of the valence electron configuration around an atom. We will only consider s and p block elements (main group) and consequently only be concerned with s and p orbitals.
Carbon - 1s22s22p2 - four valence electrons
Electron dot structure - valence electrons are represented by dots placed around the chemical symbol. Electrons are placed up to two on each side of the elemental symbol for a maximum of eight, which is the number of electrons in a filled s and p shell. We place a single electron on each side before pairing them up (this is related to Hund's rule). Period one (hydrogen and helium) represents an exception where only a maximum of two electrons are placed on one side of the element (why is this so?).
Electron dot structures for the first two periods - Number of valence electrons related to group number.
Covalent Bonds - Sharing electrons, unlike ionic compounds where electrons are thought of being gained or lost.
Non-metals exhibit both covalent and ionic bonds
compounds with metals, non-metals generally gain en electron and become negatively charged
compounds with other non-metals, valence electrons are generally shared to achieve filled valence shell.
sharing electrons - covalent bonding - the sharing of electrons is the glue that binds atoms together.
Sometimes we use an x instead of a dot to represent an electron. This allows us to track the electrons better.
Octet rule (for s- and p-block elements) - atoms combine and form bonds either by transferring electrons to form ions or by sharing electrons in covalent bonds until each atoms is surround by 8 valence electrons. Electrons in bonds are considering in counting the electrons in both atoms involved in the bond. H and He are the exception.
How would you put together N and H to form a compound? (ammonia)
How about C and H? (methane - natural gas)
Multiple covalent bonds
N2 Triple bond
open circles represent two extra electrons from 2- charge.