Element a has seven valence electrons. how does its reactivity compare to that of element b, which has four valence electrons? element a is more reactive. element a is less reactive. element a and b have the same reactivity. element a has no reactivity

Element A is more reactive. Take Fluorine for example. Since its in group 17, it needs one more electron to have an octet. Compared with carbon, group 14 with 4 valence electrons, Fluorine wants and is able to get an electron much more easily.

altitude, density, pressure

air gets less dense the higher the altitude and also the air pressure is less as altitude rises.

the number of protons in the nucleus of a given element. has slight luster and conducts electricity at high temperatures like metal.but like a nonmetal,boron is brittle and does not conduct electricity well at low temperatures. in graphite, carbon is a soft,brittle solid.it is reflective,ductile,or malleable.