Transition metals and alkali metals have a few features in common but are different in many ways. Which of the following statements is false? (A) Transition metals produce less-colorful compounds than alkali metals. (B) Alkali metals have lower melting and boiling points than transition metals. (C) Alkali metals are not widely used as catalysts, while transition metals are. (D) Transition metals are harder and stronger than alkali metals. Or (E) transition metals have a larger number of stable oxidation states than alkali metals.
The question refers to alkali metals, which includes all elements in group one of the periodic table except hydrogen. The question also refers to transition metals. Transition metals or transition elements are all of the elements in the d block apart from those found in group 12 and all of the f-block elements, which are known as inner transition elements. The transition metals are harder and stronger than the alkali metals. So option (D), transition metals are harder and stronger than alkali metals, is a true statement. But the question asks “Which of the following statements is false?” As statement (D) is true, it cannot be the answer to this question.
Transition metals also have higher melting and boiling points than alkali metals. So option (B), alkali metals have lower melting and boiling points than transition metals, is a true statement. But as the question asks “Which of the following statements is false?,” option (B) cannot be the answer to this question.
As the alkali metals are in group one, they have one electron in their outer shell and form a one plus charge. The transition metals on the other hand have incomplete d subshells. They are in fact defined as elements whose atoms have an incomplete d subshell or that can give rise to cations with an incomplete d subshell. These incomplete d subshells are the main cause for the difference in properties between alkali metals and transition metals. That would cause transition metals to be able to exist in variable oxidation states. For example, iron can form Fe2+ or Fe3+, whereas each alkali metal can only form one stable ion, a one plus ion. So option (E), transition metals have a larger number of stable oxidation states than alkali metals, is true. But as we are looking for a false statement, option (E) is not the answer to this question.
Transition metals also make good catalysts because they change oxidation states by gaining or losing electrons within their d orbitals. This means that they can transfer electrons to speed up reactions. So option (C), alkali metals are not widely used as catalysts while transition metals are, is a correct statement. Thus, option (C) is not the answer to this question.
The oxidation state of an ion can influence the color of transition metal compounds, which have a wide variety of colors in their solid-state and aqueous solutions. For example, dissolved or aqueous Fe2+ ions tend to produce green-colored solutions, while dissolved Fe3+ ions tend to produce yellow–brown colored solutions, whilst many alkali metal compounds are white in color and colorless in solution. So option (A), transition metals produce less-colorful compounds than alkali metals, is a false statement. As the question asks us for a false statement, we can determine that (A) must be correct. So the statement about transition metals and alkali metals, which is false, is (A). Transition metals produce less-colorful compounds than alkali metals.