APA citation style: Historic American Buildings Survey, C. & Benison, G. (1933) Oakland Plantation, Mount Pleasant, Charleston County, SC. Documentation Compiled After. [Pdf] Retrieved from the Library of Congress, https://www.loc.gov/item/sc0292/.
There are 18 groups (columns) in the periodic table. Group 1 (also known as the alkali metals) is the column on the far left of the table. Elements in the same group have similar, but not identical characteristics. This is because they all have the same number of electrons in their outermost shell.
Elements in group Ia are Alkali metals; group IIa the alkaline earth metals; group VIIa the halogens; group 0 the Inert gases. The position of the elements on the periodic table is based on electron structure (which gives the similar properties that have already been described). The period of the table (which horizontal row the element is in) corresponds to the principal quantum number of the elements i.e the number of shells.