Alkaline Earths and Electron Affinity

The alkaline earth metals are a group of elements in the periodic table that include beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). When considering their electron affinity, it is important to understand what electron affinity is and how it relates to the alkaline earths.

What is Electron Affinity?

Electron affinity is the energy change that occurs when an atom accepts an electron to form a negative ion. It reflects the ability of an atom to attract and hold onto an additional electron. A higher electron affinity indicates a stronger ability to accept electrons, while a lower electron affinity suggests a weaker ability to accept electrons.

Low Electron Affinity Values of Alkaline Earths

The correct answer to the question is option 'B': The alkaline earths have low electron affinity values. This means that the alkaline earth metals have a weak ability to accept additional electrons.

Explanation

1. Atomic Size:
- The electron affinity of an atom is influenced by its atomic size. Alkaline earth metals have relatively large atomic sizes compared to other elements.
- Larger atoms have more electron shielding, meaning that the outer electrons are further away from the positive nucleus and are less strongly attracted to it.
- As a result, the alkaline earth metals have a weaker ability to attract and hold onto additional electrons, leading to lower electron affinity values.

2. Electron Configuration:
- Alkaline earth metals have a valence electron configuration of ns2, where n represents the principal quantum number.
- The ns2 electron configuration is relatively stable, as the two valence electrons occupy the s subshell, which is closer to the nucleus and more strongly attracted to it.
- This stability makes it energetically unfavorable for the alkaline earth metals to accept additional electrons, resulting in low electron affinity values.

3. Metallic Character:
- Alkaline earth metals are highly metallic in nature, characterized by their ability to lose electrons easily to form positive ions.
- This tendency to lose electrons is due to their low ionization energy, which is the energy required to remove an electron from an atom.
- The low ionization energy of alkaline earth metals indicates a lower electron affinity, as the metals are more inclined to lose electrons rather than accept them.

In conclusion, the alkaline earths have low electron affinity values due to their large atomic sizes, stable electron configurations, and high metallic character. These factors contribute to their weak ability to accept additional electrons.