The work function of an element is the energy required to...

The work function of an element is the energy required to remove an electron from the surface of the solid. The work function for lithium is $279.7 \mathrm{kJ} / \mathrm{mol}$ (that is, it takes $279.7 \mathrm{kJ}$ of energy to remove 1 mole of electrons from 1 mole of Li atoms on the surface of Li metal). What is the maximum wavelength of light that can remove an electron from an atom in lithium metal?

Key Concepts

Energy Conversion using Avogadro's Number

In many applications, energy values are provided per mole rather than per individual particle. By using Avogadro’s number, one can convert a macroscopic energy amount (per mole) into the energy per photon. This conversion is essential for applying the photon energy equations accurately when working with units like kJ/mol.

Photon Energy–Wavelength Relationship

The energy of a photon is related to its wavelength by the equation E = hc/?, where h is Planck’s constant and c is the speed of light. This relation is fundamental for linking the electromagnetic spectrum to quantum phenomena, as it allows one to calculate the minimum wavelength required for photons to have a particular energy, such as the work function of a material.

Photoelectric Effect

The photoelectric effect describes the emission of electrons from a material when it is exposed to light of sufficient energy. This phenomenon supports the quantum nature of light, demonstrating that light comes in discrete packets of energy called photons, each of which must have enough energy to overcome the material’s work function for an electron to be ejected.

Work Function

The work function is the minimum energy required to remove an electron from the surface of a material. It is a characteristic property of each material and is crucial in understanding phenomena like electron emission, because only photons with energies equal to or greater than the work function can liberate electrons from the material's surface.

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