Final answer:
Arsenide atoms are surrounded by five atoms of gallium due to the difference in their electron configurations and the need for both elements to achieve a stable state.
Step-by-step explanation:
Arsenide atoms are surrounded by five atoms of gallium because of the difference in their electron configurations and the need for both elements to achieve a stable state.
Gallium, with its electron configuration of [Ar]4s²3d¹04p¹, has an additional 4p electron that can form covalent bonds with the arsenic atom. Arsenic, on the other hand, has the electron configuration of [Ar]3d¹04s²4p³ and requires five additional electrons to achieve a stable electron configuration.
The bonding between arsenide and gallium results in the formation of a crystal lattice structure, with each arsenic atom surrounded by five gallium atoms, ensuring both elements achieve a stable state.