This is how platinum appears in the periodic table. rounded to the nearest whole number, what is the atomic mass of platinum? a. 78 b.117 c.195 d.273

c. 195

explanation:

in the periodic table, platinum is the chemical element with atomic number 78. it means that it contains 78 protons in its nucleus, and 78 electrons in its orbitals.

there are several isotopes of the platinum, which determine its average mass number (and so its average atomic mass). the most abundant isotopes are:

platinum-194, platinum-195 and platinum-196, which have mass number of 194, 195 and 196, respectively.

considering all isotopes, the average mass number of platinum is 195, which means that on average platinum has 195 nucleons. since each nucleon has a mass of 1 u (1 atomic unit), the average atomic mass for platinum is 195.

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.