Final answer:
The lower-left-hand section of the periodic table is significant because it contains metals with low ionization energies, such as Rb, which are highly reactive and essential for various chemical applications.
Step-by-step explanation:
The lower-left-hand section of the periodic table is significant because it contains elements with the lowest first ionization energies within their respective periods. As one moves left across a period (row) or down a group (column), ionization energy decreases. Therefore, the element at the bottom-left corner, rubidium (Rb), would have the lowest first ionization energy of the six-element rectangle on the far-left columns. This region of the periodic table predominantly contains alkali metals that are known for losing their outer electron easily, making them highly reactive.
Elements like Li, Na, and K are alkali metals and have a single electron in their outermost shell which they can donate easily to other atoms, facilitating ionic bonding. This characteristic also makes them excellent conductors of electricity, and essential in various chemical reactions. Understanding the arrangement of the periodic table, including the lower-left-hand section, is crucial because it helps predict the properties and chemical reactions of these metals.