Relationship Between the Atomic Number and the Chemical Reactivity of Alkali Metals

Lithium has the smallest atomic number and is the least reactive of the alkali metals.
••• Jupiterimages/ Images

Alkali metals are white, highly reactive substances cut easily by a knife. All six are found in Group I of the periodic table, which lists elements in order of increasing atomic number. Atomic number is the number of protons found in the nucleus of an atom. Neutrons also reside in the nucleus, but have little effect on chemical reactivity. The alkali metals in increasing atomic number, are lithium, sodium, potassium, rubidium, cesium and francium.


The number of electrons in an atom also equals the atomic number. It is this number that identifies each element, imparting to it its unique chemical properties. Due to the laws of quantum chemistry, electrons occur in pairs whenever possible. Alkali metals always have one odd electron furthest from the nucleus. It is the electron involved in chemical reactivity.

Radius and Reactivity

As atomic number increases, so does an atom’s radius. The outermost electron is held less tightly and escapes more readily. Therefore, the alkali metal with the higher number is more chemically reactive. This makes francium the most reactive of the alkali metals.

Related Articles

Why Is the Periodic Table Arranged in Columns & Rows?
How Many Protons Does Calcium Have?
Does the Nucleus of an Atom Have Much of an Effect...
Which Halogen Has the Least Attraction for Electrons?
What Is the Effect of Atomic Radius on the Chemical...
Number of Protons in an Uncharged Atom
How to Determine the Valence Orbital of an Element
Relationship Between the Atomic Number & the Chemical...
How to Find the Mass Number of Bromine With 46 Neutrons
What Are the Two Major Components of an Atom?
What Is a Noble Gas Configuration?
What Affects the Atomic Radius?
Chemical Bonding Rules
Test Your Knowledge on Middle School Science
Differences Between Transition Metals & Inner Transition...
How to Calculate the Volume of Liquid in a Pipe
How to Draw a Helium Atom
What Are the Elements of Uranus?
How to Find the Neutrons in the Periodic Table