What do we call elements that always travel in pairs?

What produces wave a)sound b) heats c)transfer of energy d)vibrations

What is the wavelength of a wave with a velocity of 50 m/s and a frequency of 5hz a 250 m b 0.1 m c 10m d 0.01 m

Which formula equation represents the burning of sulfur to produce sulfur dioxide? s(s) + o2(g) 4502(9) 2h2s(s) + 302(g) —> 2h20(0) + 2502(9) 4fes2+1102 —> 2fe2o3 + 8502 2802(g) + o2(9) v205 , 2503(9)