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.
The group number of an element in the periodic table is the same as the number of electrons in its outer shell. An element in group 1 has 1 electron in its outer shell. An element in group 2 has 2 electrons in its outer shell. An element in group 7 has 7 electrons in its outer shell. An element in group 0 has a full outer shell. The number of electrons in the outer shell gives the element its chemical properties and controls its chemical reactions.