Explain the relationship between a main-group element's lettered group number (the number of the element's column) and its valence electrons. explain the relationship between a main-group element's lettered group number (the number of the element's column) and its valence electrons. the lettered group number of an element is equal to the number of valence electrons for that element. the lettered group number of an element is equal to the number of sublevels for that element. the lettered group number of a main-group element is equal to the number of sublevels for that element. the lettered group number of a main-group element is equal to the number of valence electrons for that element.