Question

The d-block sub-shell is always one shell lower than the s-block and p-block sub-shells. Assuming only the electrons in the highest energy shells count toward the set of valence electrons (is that correct?), d-block is never in the highest energy shell, and so none of the electrons in the d subshells would ever count toward the valence electrons.

Answer 1

Valence electrons are the outermost shell electrons involved in chemical bonding, and in transition metals (d-block), they include the highest energy s and the d subshells from one level lower. The d-block is one energy level lower than the corresponding s and p blocks in the periodic table. This characteristic influences the chemical properties of transition metals.

Step-by-step explanation:

The concept of valence electrons plays a crucial role in understanding the chemical properties and reactivity of elements. Valence electrons are the electrons in the outermost shell of an atom that are involved in chemical bonding. The d-block of the periodic table comprises the transition metals, which have their outermost s and nearby d subshell electrons as valence electrons.

It is important to note that the d-block subshell is always one energy level lower than the s and p subshells within the same period. This means that while the d-block is not in the highest energy shell, the electrons in the outermost s subshell and the d subshell from the previous energy level do indeed count toward the set of valence electrons for transition metals.

For example, in the case of potassium, which is in the s block, the 4s subshell begins to fill before the 3d subshell. Similarly, for rubidium, the 5s subshell starts to fill before the 4d. When considering the periodic table, the s block includes the first two columns, the p block includes the six columns on the right, the d block is the 10 middle columns, and the f block, which typically appears below the main body of the table, includes the lanthanides and actinides.

Therefore, when determining the valence electrons for transition metals, both the highest energy s and the d subshells one energy level lower are counted. This is different from the main group elements, where only the highest n level s and p subshells contain the valence electrons. This arrangement influences the chemical properties of the elements, with the d and f block elements showing some similarities to each other due to overlapping valence shells.