Question

Which of the following is considered as least noble of the noble metals?
A.Palladium
B.Gold
C.Rhodium
D.Rubidium

Answer 1

Hint: An element which has very less reactivity and does not undergo any type of chemical reaction either corrosion, oxidation or reduction etc. is known as noble. Noble metals do not have chemical activity with acids and remain in the original state even when they come in contact with strong acids. The least noble metal is a member of the platinum group.

Complete step by step answer:
The metals which show high resistance towards corrosion any other form of chemical reactivity are classified under the category of noble metals. In the periodic table, nine elements have been selected as noble elements, namely gold, ruthenium, rhodium, platinum, silver, osmium, mercury, iridium and palladium. There are a number of other metals that do not undergo corrosion and show noble metals like properties, namely titanium, copper, niobium and tantalum. But they are not considered as noble metals.
Noble metals are of great value because they are found in the earth’s crust and due to their unreactive properties are used in various metallurgical processes, namely the extraction of metals from their ores. Gold, silver and platinum are used as ornaments and jewellery as well because of their resistance to corrosion and lustre.
Palladium is known as the least noble metal of all the noble metals as it is the most reactive element of the platinum group. Under normal conditions, it combines with oxygen poorly but in powdered form it may catch fire and hence undergo a reaction.

Thus, the correct answer is A.

Note:
Normally noble metals do not get corroded in a strongly acidic mixture but they can be dissolved in a special type of acidic mixture known as aqua regia which is a 3:1 mixture of concentrated hydrochloric acid and concentrated nitric acid. Niobium and tantalum are however resistant to even aqua regia.