Original: Over the last century , the concept of valence evolved into a range of approaches for describing the chemical bond , including Lewis structures (/O1916/O) , valence bond theory (/O1927/O) , molecular orbitals (/O1928/O) , valence shell electron pair repulsion theory (/O1958/O) and all the advanced methods of quantum chemistry .
Simplified: In Chemistry , Valence ( which is sometimes called valency ) is the number of chemical bonds the atoms of a certain element can form .