Final answer:
Alkali metals are soft and easily cut due to weak metallic bonding and their increased reactivity with higher atomic numbers. They cannot be used structurally but are valuable in industrial processes due to their reactivity. They possess a unique electron configuration with a single s electron in their outer shell.
Step-by-step explanation:
Alkali metals are indeed soft and easy to cut. This characteristic is due to the metallic bonding which is weaker compared to other groups of metals. In alkali metals such as lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr), reactivity increases with increasing atomic number. This is due to the ease with which these metals can lose their lone valence electron, which leads to lower ionization energy. Consequently, alkali metals are highly reactive as oxidation occurs readily, making them difficult to isolate in their pure state.
Lithium, for example, not only is soft but also has the lowest density of any metal at 0.5 g/cm³. While their softness makes alkali metals unsuitable for structural applications, their reactivity is advantageous in certain industrial processes. Sodium's ability to reduce compounds is utilized in the production of some metals like titanium and zirconium. Alkali metals such as sodium and potassium are also abundant in Earth's crust and form compounds that are common in nature and everyday life, such as table salt. Finally, all alkali metals possess a single s electron in their outermost shell, giving them distinctive properties compared to the alkaline earth metals.