Final answer:
Elements in the second and third rows of the d-block can achieve higher oxidation numbers compared to first-row elements, due to their more complex electron configurations allowing for a wider variety of oxidation states.
Step-by-step explanation:
Elements in the second and third rows of the d-block are more likely to reach higher oxidation numbers than are those in the first row. The first row of the d-block is also known as the first transition series, comprising of transition elements in the fourth period of the periodic table, with atomic numbers 21-29. These elements have their valence electrons in d orbitals. However, as we move to the second and third rows of the d-block, the elements have more complex electron configurations and can exhibit a wider variety of oxidation states.
Oxyanions are a good example, where we see second-row elements like carbon and nitrogen typically form oxyanions with three oxygen atoms, while third-row elements like phosphorus and sulfur form oxyanions with four oxygen atoms. This pattern aligns with the observation that d-block elements in lower periods can reach higher oxidation states due to the additional d electrons available for bonding.