Periodic table

• The elements are arranged in order of increasing atomic number from left to right, each successive element has atoms with one extra proton.
• The elements are arranged in vertical columns called groups, each element in a group has atoms with the same number of outer shell electrons and similar properties.
• The elements are arranging horizontal rows called periods. The number of the period gives the number of the highest energy electron shell in an element's atoms.
• Elements in the periodic table can be divided into blocks corresponding to the highest energy sub-shell. This gives four distinct blocks, s, p, d, and f.