Mendeleev’s principle of chemical periodicity states that when the elements are arranged according to their atomic numbers. This periodic law allows elements with similar properties to appear at regular intervals. Predict the group of elements and their number of valence electrons that will combine in a 2:1 ratio to with sodium.
a. bromine, chlorine, iodine, 7
b. sulfur, selenium, polonium, 6 Eliminate
c. hydrogen, fluorine, potassium, 1
d. calcium, phosphorus, tellurium, 2