In this article it is shown that the electronegativity values of the constituent atoms of a binary compound can be used to predict the formation of fluoride and other halide glasses. For a more accurate and fundamental prediction of glass formation, a new criterion is proposed then. This new criterion, defined as the ratio of covalent bond strength to liquidus temperature, is meant to replace the electronegativity criterion. In combination with the total bond strength criterion, accurate predictions of glass formation can be made, as is shown by several examples