Question

Why does a diamond change directly from a solid state to a gaseous state? A diamond is comprised of only ionic bonds. A diamond is comprised of interspersed ionic and covalent bonds. A diamond is formed from hydrogen bonds. A diamond is hexagonal. A diamond is a network solid formed from carbon.

Answer 1

Diamond  change    directly  from  solid  state  to  gaseous   state  because  diamond  is  a  network  solid  formed  from  carbon

 Diamond   is  a  covalent  solid   which   is  formed  by  network  or  chain  of  carbon  atoms that  are  held  together  by a  covalent  bond.  That  is   each  carbon  atom  that  made  up  diamond  are  connected   to  the  next  by   a     c-c   covalent  bond

Answer 2

Diamond changes directly from a solid state to a gaseous state because diamond is a network solid formed from a carbon. The process of changing directly from solid state to a gaseous state is called sublimation. 
Diamond does not melt at 1 atm. It sublimes to vapor