Physical properties

Alkali metals share many similar properties including:

• They are shiny, soft, metals.
• They are very reactive.
• They all have one valence electron in the outermost shell which they seek to lose in order to have a full outer shell.
• They are soft enough to be cut with a knife.

So, the order of density is down the group at first decreases then increases. Note:According to periodic properties of the elements of the second period (Li, B, Be) and third period (Mg, Al, Si) elements which are diagonally present with each other in the periodic table, show some similar kind of chemical properties.

one valence electron

+1

Since alkali metals have a large atomic size and low atomic weight, they have low density.

lithium

The reactivity of alkali metals increases from the top to the bottom of the group, so lithium (Li) is the least reactive alkali metal and francium (Fr) is the most reactive.

Alkali metals are among the most reactive metals. This is due in part to their larger atomic radii and low ionization energies. They tend to donate their electrons in reactions and have an oxidation state of +1. All these characteristics can be attributed to these elements’ large atomic radii and weak metallic bonding.

Group 1 elements are called alkali metals because their oxides are soluble in water and group 2 elements are called alkaline earth metals as their oxides form in the earth and are water soluble.

Alkali metals react with water to produce heat, hydrogen gas, and the corresponding metal hydroxide. The heat produced by this reaction may ignite the hydrogen or the metal itself, resulting in a fire or an explosion. The heavier alkali metals will react more violently with water.

Alkaline Earth metals are very reactive because they readily give up their two valence electrons to achieve a full outer energy level, which is the most stable arrangement of electrons. Reactivity increases from the top to the bottom of the group.