If you use the terms alkali and alkaline in a non-scientific way, they mean basically the same ‘” a substance that has a higher pH level than 7. It can also be interchangeably used with base. On the other hand, chemically speaking, there is a difference between alkali and alkaline. With the differences in its placement in the table of elements is already a big thing for a great number of chemists.
Alkali is the term used for any of the elements in the first group in the Periodic Table. Besides Hydrogen, which is a gas, Alkali metals include Lithium, Potassium, Rubidium, Caesium and Francium. In looking at the properties of these elements, we see that they have one free revolving electron at the element’s last ring, thus they are put in group 1 of the IUPAC Table of Elements. Alkali metals are silvery in appearance, if not with a golden appearance. These elements are known to be highly reactive and should be stored with the utmost care, Â like kerosene. You won’t find this type of element in nature.
The term ‘Alkaline’ is used for the Alkaline Earth Metals in the Periodic Table of Elements. These elements are called ‘earth metals’ because they are hard to melt even at a high temperature. Unlike the Alkali elements that have one free electron, Alkaline Earth Metals are found in Group 2 of the IUPAC system Table of Elements, with two free electrons. The elements in this group are Beryllium, Magnesium, Calcium and Strontium.
When it comes to chemical properties, the valence or the free electron at the end of both Alkali and Alkaline metals are what separate one from the other. Alkali metals can form strong bases more rapidly than Alkaline Earth Metals. Another difference between Alkali and Alkaline lies in the fact that Alkaline Earth Metals elements have a higher ionization energy and a smaller ring because of the fact they have an extra electron.
Summary:
1. The words alkali and alkaline can mean the same thing if you use them it in a non-chemical conversation. Basically, alkali is the noun while alkaline is the adjective.
2. If you speak of alkali and alkaline in chemical terms, there is a tremendous difference.
3. Alkali metals are elements found in the first group of the IUPAC Table of Elements. All the elements in this table are elements with one valence electron, and with the exclusion of hydrogen, these are elements that have a silvery if not golden appearance.
4. Alkaline Earth Metals are solid and it require a great deal of energy in order to turn  these elements into liquid. These elements are found in the second row or second group of the IUPAC system’s Table of Elements. The two valence electrons make Alkaline Earth Metals give more ionization energy than alkali metals.