While it is true that copper has multiple energy levels and only one valence electron, several factors contribute to its lower reactivity compared to hydrogen and sodium:
Effective Nuclear Charge: The effective nuclear charge is the net positive charge experienced by an electron in an atom. In copper, despite having multiple energy levels, the 3d and 4s electrons shield the valence electron from the full positive charge of the nucleus, reducing the effective nuclear charge. As a result, the attraction between the nucleus and the valence electron is weaker, making it less likely for copper to readily donate its electron.
Electron Configuration: Copper's electron configuration is [Ar] 3d^10 4s^1. The filled 3d subshell provides additional stability to the atom. It requires a significant amount of energy to remove an electron from the 3d subshell, making copper less likely to lose its valence electron.
Ionization Energy: Ionization energy is the energy required to remove an electron from an atom. Copper has a higher ionization energy than hydrogen and sodium, meaning it takes more energy to remove its valence electron. This higher ionization energy makes copper less likely to donate its electron compared to hydrogen and sodium.
Electronegativity: Electronegativity is a measure of an atom's ability to attract electrons in a chemical bond. Copper has a higher electronegativity than hydrogen and sodium, indicating a greater tendency to attract electrons rather than donate them.
These factors collectively contribute to copper's lower reactivity compared to hydrogen and sodium. Copper tends to form compounds and participate in reactions that involve the acceptance of electrons rather than donation. It can form stable compounds with elements that readily donate electrons, but its intrinsic properties make it less likely to act as a strong reducing agent.