Element Reactivity
Why Are Certain Elements More Prominent in Chemical Reactions?
Written By: Krish Patel
A few years ago, my science teacher showed my class a video of Potassium metal being dropped in water; I found it very entertaining. This sounds normal, but to my surprise, there was a miniature explosion in the water with fire and sparks; the piece even flew out of the container. It amazed me that such a simple experiment caused such a violent reaction. What determines the reactivity of certain elements in the presence of certain compounds? The answer lies in certain characteristics of elements.
All elements have electrons, which reside in probability clouds that orbit around the nucleus. Depending on the number of protons, elements have different numbers of electrons, and neutral atoms have the same number of protons and electrons. The electrons orbit in areas called shells. The outermost shell is called the valence shell, and electrons in it are called valence electrons. This is the most important shell in terms of chemical reactions (sorry other shells, you guys are a little irrelevant for this concept). You might have heard of the octet rule, which basically says that atoms prefer having eight electrons in their valence shell (who knew atoms were picky too? I know). Unfortunately, only noble gases have eight electrons in their valence shell, so everybody else is sad, and some elements show this sadness in different ways than others. Alkali metals, for instance, have one valence electron, so they will do almost anything to get rid of it, making them some of the most reactive elements. This is why Potassium explodes when it reacts with water, it wants to get rid of its electrons, but it does so in an overreactive manner (chill out Potassium). This is a trend for metals; atoms with less electrons in their valence shell will be more reactive. For non-metals, noble gases don’t react since they are perfect. Halogens, just one column over, however, are the most reactive, as they are one electron away like alkali metals from becoming full. Electronegativity, a fancy word for the tendency to attract electrons, demonstrates this trend for nonmetals like halogens because they are desperate to attract one final electron, which makes them incredibly reactive. For metals, the opposite is true. Elements with less electrons are more reactive because they are much more willing to lose the electron or electrons as they are so close to having a full valence shell. The periodic table shows all of these trends. Elements further to the ends of the table are generally more reactive, with the exception of noble gases.
Element reactivity might sound boring or pointless, but it is very important. Without knowing reactivity, we might not know how certain things could react in the presence of a different environment, and these reactions could possibly be detrimental to our health. You could die if you didn’t know hydrogen would explode in the presence of fire. Liquid hydrogen can even explode with air! Reactivity is fundamental to chemistry, and it is central to producing both beneficial and simply aesthetic chemical reactions.
Works Cited
Libretexts. (2023, January 30). The octet rule. Chemistry LibreTexts. https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Electronic_Structure_of_Atoms_and_Molecules/Electronic_Configurations/The_Octet_Rule#:~:text=The%20octet%20rule%20refers%20to,and%20form%20more%20stable%20compounds.
Monahan, C. (n.d.). Predicting reactivity using the periodic table - overview. expii. https://www.expii.com/t/predicting-reactivity-using-the-periodic-table-overview-8587
