On the periodic table, the seven horizontal rows are called periods. On the left-hand side of the periodic table, the row numbers are given as one through seven. Moving across a period from left to right, the atomic number of the elements increases.Know More
Rows six and seven contain elements called transition elements, which are subdivided into the actinide and lanthanide series. While the elements numbered 58 through 71 are the lanthanide series, elements with the numbers 90 through 103 are the actinide series.
The vertical columns on this table are called groups. Groups are sometimes called families because the elements in them share certain physical and chemical properties. In the older system, these groups were given the Roman numerals I through VIII. In the new system, they are designated as groups 1 through 18.Learn more about Atoms & Molecules
Mendeleev arranged the periodic table in order of increasing atomic weight of the elements. He determined that there was a pattern when he arranged these elements into horizontal rows.Full Answer >
Co in the periodic table of elements is cobalt. Located in group nine, period four of the periodic table, this transition metal has an atomic number of 27 and an atomic weight of 58.9. It is a hard element that appears bluish-gray in color.Full Answer >
Dmitri Mendeleev is widely credited as the creator of the periodic table. A charismatic Russian scientist who was fascinated by chemistry, Mendeleev came up with the idea to organize chemical elements according to their atomic number and other properties. The first periodic table was published by Mendeleev in 1869.Full Answer >
Neon is the least reactive element on the periodic table. As a noble gas, neon is colorless and odorless with extremely low reactivity in its natural state. Neon has an atomic number of 10.Full Answer >