APA stands for American Psychological Association. APA is often called name-and-date style. APA Format is widely used in psychology, business, education, engineering and the social sciences.The latest APA manual is called: Publication Manual of the American Psychological Association, sixth edition.
The elements are arranged in order of their increasing atomic number. Also the columns or groups are arranged by the number of valence electrons that a element has. For example, all the elements in column 1 have 1 valence electron meaning it has 1 electron in its outer shell. Elements in the same column tend to have similar if not identical properties.
The periodic table is an arrangement of the chemical elements, organized on the basis of their atomic numbers, electron configurations and recurring chemical properties.Elements are presented in order of increasing atomic number.The standard form of the table consists of a grid of elements, with rows called periods and columns called groups. The history of the periodic table reflects over a century of growth in the understanding of chemical properties.he Russian chemist Dmitri Mendeleev was the first scientist to make a periodic table similar to the one used today. Mendeleev arranged the elements by atomic mass, corresponding to relative molar mass.