Question

Which one of the given elements shows the maximum number of different oxidation states in its compounds?
A. $Am$
B. $Fm$
C. $La$
D. $Gd$

Answer 1

Hint: Oxidation state indicates the degree of oxidation for an atom in a chemical compound. It is also referred to as oxidation number. It is the total number of electrons removed or added to an atom.

Step by step answer: Let’s first know about the elements given in the option.
$Am$ or Americium is a synthetic radioactive chemical element having atomic number 95. It is a transuranic member of the actinide series and is located under the lanthanide element europium in the periodic table and thus was named after Americas by analogy. It is the third element in the transuranic series. It is a relatively soft radioactive metal with silvery appearance. Mostly its oxidation is +3 in chemical compounds. It has various other oxidation states ranging from +2 to +7.
$Fm$ or Fermium is a synthetic element with atomic number 100. It is an actinide and the heaviest element that can be formed by neutron bombardment of lighter elements and also the last element that can be prepared in macroscopic quantities. A total of 19 isotopes are known for Fermium. It has +3 oxidation state in general but can also possess +2 oxidation state.
$La$ or Lanthanum is a chemical element having atomic number 57. It is a soft, ductile silvery white metal that tarnishes slowly when exposed to air and is soft enough to be cut with a knife. It is a part of the eponym of the lanthanide series. It is counted as one of the rare earth elements. It is not particularly toxic to humans but does show some antimicrobial activity. The element has +3 oxidation state.
$Gd$ or Gadolinium is a chemical element with atomic number 64. Gadolinium is a silvery white metal when oxidation is removed. It is slightly malleable and is a ductile rare earth element. It reacts with atmospheric oxygen to form a black coating. It is found in nature in oxidized form. It has oxidation states +1, +2 and +3.
From the above information we can see that americium has the highest number of oxidation states.

Therefore, the correct answer is option A.

Note: Compounds have different oxidation states and based on the chemical reaction oxidation state is defined. But there is an oxidation state for every compound that is generally used in most reactions. For e.g. $Am$ has many oxidation states but mostly +3 is used.