Which element is most likely a solid with dull appearance is and poor conductor of electricity

non-metals

non-metals example:- oxygen and hydrogen

Explanation:

hope this helps you!!

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.

it is the most commonly accepted one