Period 4 and period 5 are given the name long periods of the periodic table because there are 18 elements in these periods. The elements of the long periods are shown in tables below. Period 4 elements refer to the chemical elements found in the fourth row or period of the periodic table. This period includes elements ranging from potassium (K) to krypton (Kr), with atomic numbers 19 to 36. The fourth period contains 18 elements beginning with potassium and ending with krypton – one element for each of the eighteen groups. It sees the first appearance of d-block (which includes transition metal s) in the table. Period 4 of the periodic table refers to the fourth horizontal row of chemical elements, starting with potassium (atomic number 19) and ending with krypton (atomic number 36). This period contains the heaviest element which occurs naturally on Earth, plutonium. All of the subsequent elements in the period have been synthesized artificially. A period 4 element is one of the chemical elements in the fourth row (or period) of the periodic table of the chemical elements. Q: Do elements in the same period have similar properties? A: No. Elements in the same period have different properties because they have different numbers of valence electrons. Members of Period 4 include important industrial metals and biologically significant elements. Elements: K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Br, Kr Interactive periodic table showing names, electrons, and oxidation states. Visualize trends, 3D orbitals, isotopes, and mix compounds. Fully descriptive writeups. The fourth period contains 18 elements beginning with potassium and ending with krypton – one element for each of the eighteen groups. It sees the first appearance of d-block (which includes transition metals) in the table.