Why does sulfur have a higher melting point than phosphorus

What is the number of moles of chemical units represented by 9.03x10^24? and how do i show work? (dumb it down )

Consider the elements bromine and chlorine; which elements has a larger ionic radius ?

Consider the following reaction at equilibrium. 2co2 (g) 2co (g) + o2 (g) h° = -514 kj le châtelier's principle predicts that the equilibrium partial pressure of co (g) can be maximized by carrying out the reaction a. at high temperature and high pressure b. at high temperature and low pressure c. at low temperature and low pressure d. at low temperature and high pressure e. in the presence of solid carbon