State the periodic law. How did the periodic law lead to the periodic table?
Solution : Rhodium is a chemical element with symbol Rh. It is a member of the platinum group. Naturally occurring rhodium i s usually found as the fr metal. It is one of the rarest and most valuable precious metals and is a noble metal, resistant to corrosion. Rhodium is used in jewelry and for decorations and also used as an alloyin g agent for hardening and improving the corrosion resistance of platinum and palladium. (a) What is the radius of a rhodium atom in angstroms (Å) and in meters (m) Given, Diameter of a Rhodium (Rh) atom = 2.7×10 cm. -8 We use the following conversion factors, to determine the radius of a rhodium atom in angstroms (Å) and in meters (m) 1 Å = 10 cm. 2 1 m = 10 cm The radius of Rh atom in angstroms (Å) i s : = = 1.35Å Therefore, radius of Rh atom in angstroms (Å) is 1.35Å. The radius of Rh atom in meters (m) is : = = 1.35 ×10 -1m Therefore, radius of Rh atom in meters (m) is 1.35 × 10-1m. (b) How many Rh atoms would have to be placed side by side to span a distance of 6.0 mm To find the number of Rh atoms required to be placed side by side to span a distance of 6.0mm, we need to find the distance covered by one Rh a tom. Therefore, the distance covered by one Rh atom is equal to its diameter. -8 Given, diameter of Rh atom = 2.7 × 10 cm = -4 = 2.7 10 m Number of atoms required to be placed side by side to span a distance of 6.0mm is : = 2.22× 10 Rh atoms. Therefore, 2.22× 10 Rh atoms is required to be placed side by side to span a distance of 6.0mm. (c) If you assume that the Rh atom is a sphere, what is the volume in m3 of a single atom Volume of a sphere is given by formula : where, r = radius of the atom. So, we calculate the volume by substituting the values in the formula : Here, we have got the diameter of the Rh atom. Radius is half the diameter, so radius of Rh atom is 1.35 ×10 m. where, 3.14 is constant value of . = 1.031 ×10 m .-29 3 -29 3 Therefore, the volume of single Rh atom in m3 is 1.031 × 10 m .