Group 1, also known as alkali metals, is a group of metals that is located on the far left vertical column of the periodic table.
All alkali metals have one electron in their outermost shell, so they share some physical properties:
The properties of alkali metals are largely determined by their atomic structure. As alkali metals only have one electron in their outer shell, they are highly reactive.
Atoms seek stability by achieving a complete outer electron shell. When alkali metals react, they easily lose their single outer electron, forming a positive ion with a +1 charge. As alkali metals can easily lose their outer electron, they are highly reactive, so they tend to form compounds with other elements easily.
As you go down group 1, there are noticeable trends in the properties of these metals. This is due to an increase in the number of electron shells, which results in the outermost shells being further away from the nucleus.
The greater the distance between the outer electrons and the nucleus, the weaker the attraction between them. This means that less energy is required to separate the electrons from the nucleus, making the metals more reactive.
Reactivity refers to how easily a chemical substance undergoes a chemical reaction. Alkali metals are highly reactive, meaning they can easily lose their single outer electron to form ionic compounds with non-metals.
The melting points of alkali metals also decrease as you move down the group. This is due to the weakening of the forces of attraction between the negatively charged electrons and the positively charged nucleus. However, even at their highest, the melting points of alkali metals are relatively low compared to other metals.
Also, alkali metals become softer as you move down the group, although potassium (K) is an exception, being softer than sodium (Na).