(b)原子間距離由無窮遠接近到鍵結距離,形成金屬的過程為放熱還是吸熱，並請說明理由。

5. To improve the physical and chemical properties of metal materials, it is common to introduce heteroatoms into the parent material to form a solid solution during metallurgy. Please describe what types of solid solutions that heteroatoms can form, and describe what factors affect the solubility of these heteroatoms in the solid solutions. [10分]