How to learn chemistry through hentai: let's start from the assumption that an atom is similar to an oocite in the process of fertilization: there is a central nucleus (oocite) surrounded by various electrons (sperms).
Therefore, electrons = sperms.
Since any covalent bonding implies an electron (i.e.: sperm) exchange, every molecule can be thought as a sexual relationship between various people, the atoms. To determine the sex of atoms it's helpful to take into account the fact that each element in the periodic table is determined by a value called "electronegativity" which states the tendency to attract electrons (i.e.: the sperm) in a bonding (sexual intercourse), while its opposite (i.e.: the tendency to donate electrons / sperms) is called "electropositivity" ... Since in a sexual relationship, usually the one who "gives" the sperm is the male and the one who receives it is the female, we can make the following equivalence:
electronegativity = femininity
elettropositivity = masculinity
in other words, the most electronegative elements (like nonmetals) are females, while the most electropositive ones (like metals) are males (by convention, the electronegativity of hydrogen will be taken as the boundary: elements more electronegative than hydrogen will be considered females, while less electronegative males). Furthermore, high electronegativity/positivity values imply high reactivity, meaning high tendency to form and/or break chemical bondings; in other words, the higher an element's electroneg./electropos. value is, the higher its "libido": for example, halogen elements (the most electronegative ones) can be thought as nymphomaniacs, while alkaline metals (the most electropositive ones) as perverts.
Now let's talk about bonds: they can be heteropolar (when electrons tend to be concentrated around only 1 atom) or homopolar (when electrons are equally shared). The first case is when the participating atoms have very different values of electronegativity (i.e.: when the participants are of different sexes), the second case is when their electronegativity values are very similar (i.e.: when the participants are of the same sex).
heteropolar bond = heterosexual relationship
homopolar bond = homosexual relationship (that can be yaoi when the participants are both males, or yuri when the participants are both females)
All of this can lead to fascinating consequences, for example the fact that the air we breath can be thought as a giant yuri orgy, while most of metal objects like a huge yaoi orgy, and lots of other concepts that are best left to the reader's imagination...