Do electrons in covalent bonds always necessarily obey the octet rule? Always?
The elements in borons row do not always follow the octet rule as in the case of boron fluoride as boron is in the center of the periodic table and will usually only bond to fill up its outer shell with 6 electrons. Additionally, elements with can form expanded octets which can share more than 8 electrons such as phosphorous pentachloride. Of course hydrogen only has 2 electrons to bond with so it is also an exception to the octet rule.