Which element has the greatest density at stp?
(1) scandium (3) silicon
(2) selenium (4) sodium

            Selenium has the greatest density at STP.

                   According to Ideal gas equation,

                                                P V  =  n R T

where;

             n =  m/M

Therefore,

                                                P V  =  m R T / M

Rearranging,

                                                P M  =  (m/V) R T

Also,

             m/V  =  density  = d

So,

                                                P M  =  d R T

Solving for density,

                                                d  =  P M / R T

According to this equation density is directly proportional to Molar mass of a substance. Hence, the Atomic masses of given compounds are listed below,

                                                Scandium =  44.96 g.mol⁻¹

                                                Selenium  =  78.97 g.mol⁻¹

                                                Silicon  =  28.09 g.mol⁻¹

                                                Sodium  =  22.99 g.mol⁻¹

Therefore, selenium having the greatest Atomic Mass will have the greatest density. The densities of given elements are as follow;

                                                Scandium =  2.98 g.cm⁻³

                                                Selenium  =  4.81 g.cm⁻³

                                                Silicon  =  2.33 g.cm⁻³

                                                Sodium  =  0.96 g.cm⁻³

in chemistry, a solution’s concentration is how much of a dissolvable substance, known as a solute, is mixed with another substance, called the solvent. the standard formula is c = m/v, where c is the concentration, m is the mass of the solute dissolved, and v is the total volume

metals are good conductor of electricity. it has free electrons on their surface. according to electron pool theory, each atom present in a metal crystal losses all of its valence electron and as a result a pool of free is form. these pool of electrons are free to move and   conduct electricity easily   while making metal as good conductor.

the correct answer is a. the ability of electrons to flow throughout the metal.

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