The reactivity of copper is low because of its

high enthalpy of sublimation and high ionization energy

The correct answer is option 2. high enthalpy of sublimation and high ionization energy.

The reactivity of copper (Cu) is relatively low, and this can be attributed to its enthalpy of sublimation and ionization energy. Copper has:

A high enthalpy of sublimation

A high ionization energy

These factors combined contribute to its low reactivity. Let us break down why:

High Enthalpy of Sublimation

Enthalpy of sublimation is the energy required to convert one mole of a solid element into gaseous atoms.

Copper's Enthalpy of Sublimation: Copper has a high enthalpy of sublimation, meaning it takes a lot of energy to break the metallic bonds in solid copper to produce individual \(Cu\) atoms in the gas phase. This high energy requirement makes it energetically unfavorable for copper to undergo reactions that would require it to be in the gaseous atomic form.

High Ionization Energy

Ionization energy is the energy required to remove an electron from a neutral atom in the gas phase.

Copper's Ionization Energy: Copper has a relatively high first ionization energy. This is the energy needed to remove the outermost 4s electron from a copper atom. The high ionization energy indicates that copper holds onto its electrons tightly, making it less likely to lose electrons and participate in reactions that involve the formation of \(Cu^+\) or \(Cu^{2+}\) ions

Combined Effect on Reactivity

Stability of Copper: Because of the high enthalpy of sublimation, copper does not easily transition from its solid form to the gas phase, which is a precursor for many high-energy reactions. Additionally, due to its high ionization energy, copper does not readily lose electrons to form cations. Both factors contribute to copper's low reactivity.

Comparison with Other Metals: Metals with lower enthalpy of sublimation and lower ionization energy tend to be more reactive because they can more easily transition into the gas phase and lose electrons to form cations. For example, alkali metals like sodium \((Na)\) and potassium \((K)\) have lower enthalpy of sublimation and ionization energy, making them much more reactive than copper.

Practical Implications

Resistance to Corrosion: The low reactivity of copper means it is less prone to oxidation and corrosion compared to more reactive metals. This property makes copper useful in applications where durability and resistance to environmental factors are important, such as in electrical wiring and plumbing.

Noble Character: Copper is often referred to as a "noble" metal because of its low reactivity, similar to precious metals like gold and silver. This noble character is directly linked to its high enthalpy of sublimation and high ionization energy.

In summary, the low reactivity of copper can be attributed to the combination of its high enthalpy of sublimation and high ionization energy. This makes it energetically less favorable for copper to undergo reactions that would involve breaking its metallic bonds or losing electrons. Thus, the correct explanation is: high enthalpy of sublimation and high ionization energy.