Elements of the periodic table can exist in various forms in nature, categorized as monoatomic, diatomic, or polyatomic based on their stability. Monoatomic elements are those that are stable when found alone, indicated by the prefix "mono," meaning one. Examples include lithium (Li), magnesium (Mg), and zinc (Zn), which exist independently without forming bonds with other atoms.
Diatomic elements, on the other hand, are stable as pairs, as suggested by the prefix "di," meaning two. A mnemonic to remember these diatomic elements is "Have No Fear Of Ice Cold Beer," which corresponds to the elements: hydrogen (H2), nitrogen (N2), fluorine (F2), oxygen (O2), iodine (I2), chlorine (Cl2), and bromine (Br2).
Lastly, polyatomic elements are stable in groups larger than two, with "poly" meaning many. Notable examples include phosphorus (P4), sulfur (S8), and selenium (Se8). Elements in the same group of the periodic table often share similar chemical properties, which is evident as sulfur and selenium both exist as octatomic molecules.
In summary, understanding the forms in which elements exist—monoatomic, diatomic, and polyatomic—provides insight into their stability and behavior in nature.