Final answer:
Gold (Au) is the correct answer as it is a relatively inactive solid metal due to its inert nature. It does not react easily with other substances, making it different from more reactive metals such as aluminum or alkali metals, and is often found in its metallic state.
Step-by-step explanation:
The question asks which among Al (Aluminum), Au (Gold), Br (Bromine), Ca (Calcium), Cs (Cesium), F (Fluorine), H (Hydrogen), He (Helium), Hg (Mercury), I (Iodine), K (Potassium), Mg (Magnesium), Na (Sodium), O (Oxygen), P (Phosphorus), S (Sulfur), and Si (Silicon) is a relatively inactive solid metal. The answer is Au (Gold).
Gold is part of the third transition series in the d-block elements, recognized for being inert and not reacting easily with other substances, which makes it a relatively inactive solid metal. Its unreactive nature is why it is often found in its native (metallic) state and has been valued for jewelry and currency. Unlike alkali metals such as sodium and potassium, or halogens like fluorine, gold does not react with water or oxygen in the air, a property that contributes to its passivity and longevity as a metal.
In comparison to the other options given, He (Helium) is a noble gas and therefore not a metal, Al (Aluminum) is relatively reactive, especially in fine powders, and while it forms a passivating oxide layer, it is not as inert as gold. Si (Silicon) is not classified as a metal but as a metalloid, and while it is relatively inactive, it does not fit the criteria like gold does.