's left-step periodic table is the most widely used alternative to the traditional depiction of the periodic system. It organizes elements according to an idealized orbital filling. For example, the elements Sc to Zn are shown as a 3d block implying orbital occupancy 4s2 3dx, although it is now known that Cr actually has orbital occupancy 4s1 3d5 and Cu has 4s1 3d10. , these blocks fill out in the order of s, p, d, and f. The left-step periodic table is organized according to a reversal of this order, so that the true order is maintained through a proper reading. Compared to the common layout, the left-step table has these changes:
Helium is placed in group 2.
Groups 1 and 2, including elements 119 and 120 in extended period 8, are moved to the right side of the table.
The s-block is shifted upwards one row, and all elements not in the s-block are now one row lower than in the standard table. For example, most of the fourth row in the standard table is the fifth row in this table.
In the result, the order is still consistently by atomic number, 1-120.
Two-dimensional spiral (Benfey, 1964)
In Theodor Benfey's periodic table the elements form a two-dimensional spiral, starting from hydrogen, and folding their way around two peninsulas, the transition metals, and lanthanides and actinides. A superactinide island is already slotted in.
's 3-D periodic table consists of four connected billboards with the elements written on the front and the back. The first billboard has the group 1 elements on the front and the group 2 elements at the back, with hydrogen and helium omitted altogether. At a 90° angle the second billboard contains the groups 13 to 18 front and back. Two more billboards each making 90° angles contain the other elements.
Ronald L. Rich has proposed a periodic table where elements appear more than once when appropriate. He notes that hydrogen shares properties with group 1 elements based on valency, with group 17 elements because hydrogen is a non-metal but also with the carbon group based on similarities in chemical bonding to transition metals and a similar electronegativity. In this rendition of the periodic table carbon and silicon also appear in the same group as titanium and zirconium.
ADOMAH (Valery Tsimmerman, 2006)
The ADOMAH table is an adaptation of the left step table. Each strictly vertical column of the table has the same value of the principal quantum numbern. For example, n = 3 for Fe. Each block of elements has the same value of the secondary quantum numberl. For example, l = 2 for Fe. Each element entry together with all preceding elements corresponds to the electron configuration of that element. For example, the electron configuration of Fe is determined by starting at H, which is 1s1, and counting in atomic number order. This gives a configuration of 1s2 2s2 2p6 3s2 3p6 4s2 3d6 or, in short form, 4s2 3d6. The four blocks of the Adomah table can be rearranged such that they fit, equidistantly spaced, inside a regular tetrahedron. The latter, in turn, fits into a cube.
Other
A chemists' table with an alternative positioning of hydrogen, helium and the lanthanides was published by EG Marks and JA Marks in 2010.
Variants of the classical layout
From Mendeleev's original periodic table, elements have been basically arranged by valence and the repetition therein. Over the years and with discoveries in atomic structure, this schema has been adjusted and expanded, but not changed as a principle. The oldest periodic table is the short form table by Dmitri Mendeleev, which shows secondary chemical kinships. For example, the alkali metals and the coinage metals are in the same column because both groups tend to have a valence of one. This format is still used by many, as shown by this , which includes all elements and element names until roentgenium. H. G. Deming used the so-called long periodic table in his textbook "General Chemistry", which appeared in the US for the first time in 1923, and was the first to designate the first two and the last five main groups with the notation "A", and the intervening transition groups with the notation "B". The numeration was chosen so that the characteristic oxides of the B groups would correspond to those of the A groups. The iron, cobalt, and nickel groups were designated neither A nor B. The noble-gas group was originally attached to the left side of the periodic table. The group was later switched to the right side and usually labeled as group VIIIA.
Extension of the periodic table
In the extended periodic table, suggested by Glenn T. Seaborg in 1969, yet unknown elements are included up to atomic number 168. Theoretical periods above regular period 7 are added. In the research field of superatoms, clusters of atoms have properties of single atoms of another element. It is suggested to extend the periodic table with a second layer to be occupied with these cluster compounds. The latest addition to this multi-story table is the aluminium cluster ion, which behaves like a multivalent germanium atom.
