The Modern Periodic Table
The modern Periodic Table is based n one prodcued by the Russian chemist, Mendeleev in 1869. He organised the 61 elements he knew at the time and organised them into horizontal rows and vertical columns. Similar elements were placed underneath each other in the columns. Mendeleev left gaps in his Periodic Table as he knew that new elements were to be discovered, and he predicted what they would be by relating the properties.
In Mendeleev's Periodic Table the elements were arranged in order of increasing relative atomic mass. This may not always apply to the modern Periodic Table, as it's atomic number which really determines the place of an element. (Te; Ar = 128, comes before I; Ar = 127). With the exception of hydrogen, the elements are organised into four blocks: s, p, d and f.
Elements in the same block show general similarities. All the non-metals are in the p block; many of the reactive alkali metals (sodium and potassium) are in the s block. Vertical columns are called groups. Group 1 = alkali metals, Group 7 = halogens, Group 0 = noble gases. Horizontal rows are called periods. As they cut across groups, there are fewer common features among the elements of…