the octet rule states that elements prefer to be surrounded by 8 electrons. there are certainly elements that don't obey the rule, but many of the main group elements ( not transition metals) do.
the number of valence electrons can be determined usually from the group the elements are in on the periodic table. The noble gases have 8 (Group VIII), halogens have 7 (Group VII), oxygen selenium and sulfur have 6 (Group VI), N and P have 5 (Group V), C has 4 (Group IV), etc. The noble gases have a full octet (four lone pairs), so they are inert. Most other elements have to combine with other atoms to achieve an octet of 8 electrons.
Start by adding the valence electrons to the element one at a time until it has four around it. If you're working with, say N, there will be 5 V.E. Once you add 4 single electrons around N, you have one more left over and this one will combine with one of the single electrons to give a lone pair. So you have a N with one lone pair and three single electrons around it. In order to achieve the octet rule, you need 3 more electrons, which can be gained by combining each of the single electrons with something else, say H atom (has one valence electron b/c Group I). When you add the H atom to the three single electrons on N, you get NH3. So, the N has one lone pair (2 electrons) and 3 covalent bonds (at 2 electrons each) for a total of 8 electrons around N.
The vagina, sagittal section showing the location of the vagina and its relationship to the cervix,
Relative energies of covalent bonds and noncovalent interactions
The relationship between RH and temperature.
The “inside positive” rule
Relationship between Latitude and Income per Capita
Number line for rounding