Distinguish between thermal cracking and catalytic cracking

Write the symbol for every chemical element that has atomic number greater than 3 and atomic mass less than 12.0 u.

List four observations that indicate that a chemical reaction may be taking place

Which statement correctly describes metallic bonds? a. they form when certain atoms lose electrons and other atoms gain electrons. b. they involve an attraction between anions and cations. they always involvpoth a metal and a nonmetal. d. they can only form between atoms of the same element. e. they form because electrons can move freely between atoms.