How does electron affinity depend upon (a) Atomic size (b) Nuclear charge (c) Electronic configuration

Understanding how the size of an atom influences its tendency to accept an additional electron is critical when exploring electron affinity. Simply put, atomic size refers to the distance between the nucleus and the outermost orbitals of an atom. Smaller atoms, with electrons closer to the nucleus, generally have higher electron affinities because the added electron can be more tightly held due to the strong attraction from the nucleus. In larger atoms, the outer electrons are situated further away, resulting in weaker nuclear attraction and, therefore, a lower electron affinity.

Imagine trying to attach a magnet to a metal surface: the closer the magnet is, the stronger it sticks. Similarly, in smaller atoms, an added electron 'sticks' more firmly to the atom, releasing more energy in the process.

The nuclear charge of an atom is a fundamental property that dictates its electron affinity. Nuclear charge is essentially the positive charge carried by the protons in the nucleus. Atoms with a higher nuclear charge exert a stronger pull on incoming electrons due to their greater positive charge. This results in a higher release of energy when an electron is added, translating to a higher electron affinity.

It is akin to the pull of gravity: objects with greater mass exert a stronger gravitational pull. In atomic terms, a nucleus with more protons will exert a stronger 'gravitational' pull on nearby electrons.

The electronic configuration of an atom details the distribution of electrons among the various atomic orbitals. This distribution plays a pivotal role in electron affinity. Stable configurations, such as those with fully filled or half-filled orbitals, typically result in lower electron affinities. The reason is that adding an electron to such a stable arrangement introduces a level of repulsion and instability, requiring energy input rather than release.

Conversely, if an atom is one electron away from a stable configuration, it will have a high electron affinity. The atom's natural drive towards stability means it will readily accept an extra electron with a release of energy, much like the final piece of a puzzle clicking into place effortlessly.

The concept of nuclear attraction ties intimately with electron affinity. It's the force exerted by the positively charged nucleus on the negatively charged electrons. This attraction dictates how tightly electrons are held within the atom and how readily the atom can accept another electron. A stronger nuclear attraction boosts electron affinity as it enables the atom to better stabilize the additional electron.

Think of it as a tug-of-war contest: a team (the nucleus) with a stronger 'pull' has a better chance of winning over new members (electrons) as opposed to a weaker team with less pulling power.

Delving into the realms of atomic orbitals provides insight into the electron affinity puzzle. Atomic orbitals are regions around an atom's nucleus where electrons are most likely to be found. They come in various shapes and sizes, influencing how an electron is added to an atom.

Orbitals that are further from the nucleus and have higher energy levels tend to have lower electron affinity, as the added electron will be less attracted to the nucleus and more shielded by inner electrons. In this sense, orbitals act as the 'neighborhoods' within an atom, and the desirability of the neighborhood (orbital) affects how eager an extra 'resident' (electron) would be to move in.