What is the realationship beetween atmospheric pressure and the density of the gas particles in an area of decreasing pressure

What do electromagnetic waves carry? how are they produced through which media can they move? where do they transfer energy? what do they not transfer? what do mechanical waves carry? how are they produced? through which media can they move? where do they transfer energy? what do they not transfer?

In ccl4 is there a certain length that the main atom carbon is a certain distance from the chlorine’s?

Which is the best metal to use in an alloy to increase its electrical conductivity?