Photochemical smog differs from industrial smog in that it .

It is formed only in the presence of sunlight

Explanation:

Photochemical smog is a type of smog produced when there is a reaction between ultraviolet light from the sunlight and nitrogen oxides in the atmosphere. This is seen as a brown haze, and is most prominent during the morning and afternoon, especially in heavily populated, warm cities.

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.

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.