Answer:
1.The chemical elements are arranged in order of increasing atomic number. The horizontal rows are called periods and the vertical columns are called groups. Elements in the same group have similar chemical properties. This is because they have the same number of outer electrons and the same valency.
2.Moving Across the Periodic Table. an increase in atomic size because of additional repulsions between electrons, a decrease in size because of the additional protons in the nucleus, no effect at all as the two opposing tendencies of electron repulsion and nuclear attraction balance each other out.
3.Basically the table is set up in order of increasing atomic number. This sets up an increase in physical properties as one climbs up the table. The original attempt had been to set the table up in order of increasing atomic weights, but that had some obvious anomalies with regard to chemical and physical properties.
