Block (periodic table) reactivity decreases as the atomic number increases. When a halogen combines with another element, the resulting compound is called a halide. One of the best examples of a halide is sodium chloride (NaCl). The d-block is on the middle of the periodic table and includes elements from columns 3 through 12. These elements are also known as the transition metals because they show a transitivity in their properties i.e. they show a trend in their properties in simple incomplete d orbitals. Transition basically means d orbital lies between s and p orbitals and shows a transition from properties of s
Extended periodic table and discovered that some elements indeed had different properties that break the established pattern, and a 2010 calculation by Pekka Pyykkö also noted that several elements might behave differently than expected. It is unknown how far the periodic table might extend beyond the known 118 elements, as heavier elements are predicted to be increasingly unstable. Glenn T. Seaborg suggested that the highest possible element may be under "Z" = 130, while Walter Greiner predicted that there may not be a highest possible element. There is currently no consensus on the placement of elements beyond atomic number 120 in the periodic