Question

the valence electrons of the substances atoms feel an effective nuclear charge of + 7 if the unknown substance has lower ionization energy than the chlorine what other characteristics would you expect the substance to exhibit​

Answer 1

If the nuclear charge of atoms equal to +7 and the substance has lower ionization energy than the chlorine, then element located in the seventh group and below chlorine in the Mendeleev. In all probability it is manganese. So, manganese is a metal and its oxides show both the basic and acidic properties.