Which of the following elements are transition elements: Cu, Sr, Cd, Au, Al, Ge, Co? How can this be determined?

To identify which of the elements you listed are transition elements, we first need to understand what defines a transition element. Transition elements are typically found in the d-block of the periodic table and are characterized by their ability to form variable oxidation states and to create colored compounds. They also often have unfilled d-orbitals in their elemental or common oxidation states.

Identifying Transition Elements

Let’s break down the elements you mentioned: Cu (copper), Sr (strontium), Cd (cadmium), Au (gold), Al (aluminum), Ge (germanium), and Co (cobalt).

• Cu (Copper): This is a transition metal. It has an electron configuration of [Ar] 3d¹⁰ 4s¹, allowing it to exhibit multiple oxidation states, primarily +1 and +2.
• Sr (Strontium): This is not a transition metal. It is an alkaline earth metal with the electron configuration [Kr] 5s² and does not have d-electrons in its outer shell.
• Cd (Cadmium): Cadmium is considered a transition metal. Its electron configuration is [Kr] 4d¹⁰ 5s², and it can exhibit a +2 oxidation state.
• Au (Gold): Gold is a transition metal. It has an electron configuration of [Xe] 4f¹⁴ 5d¹⁰ 6s¹ and can exhibit oxidation states of +1 and +3.
• Al (Aluminum): Aluminum is not a transition metal. It is a p-block element with the electron configuration [Ne] 3s² 3p¹ and typically exhibits a +3 oxidation state.
• Ge (Germanium): Germanium is also not a transition metal. It is a p-block element with the configuration [Ar] 3d¹⁰ 4s² 4p² and does not have the characteristics of transition metals.
• Co (Cobalt): Cobalt is a transition metal. Its electron configuration is [Ar] 3d⁷ 4s², and it can exist in multiple oxidation states, commonly +2 and +3.

Summary of Transition Elements

From your list, the transition elements are:

• Cu (Copper)
• Cd (Cadmium)
• Au (Gold)
• Co (Cobalt)

In contrast, Sr (Strontium), Al (Aluminum), and Ge (Germanium) do not qualify as transition elements. The key to determining whether an element is a transition metal lies in its position in the periodic table and its electron configuration, particularly the presence of d-orbitals that can participate in bonding and oxidation state variation.