Կապշեք ուղղակի, երբ իմանաք, թե ով է եղել Սարգիս Գրիգորյանի նախկին կինը Կապշեք ուղղակի, երբ իմանաք, թե ով է եղել Սարգիս Գրիգորյանի նախկին կինը Կապշեք ուղղակի, երբ իմանաք, թե ով է եղել Սարգիս Գրիգորյանի նախկին կինը Կապշեք ուղղակի, երբ իմանաք, թե ով է եղել Սարգիս Գրիգորյանի նախկին կինը Կապշեք ուղղակի, երբ իմանաք, թե ով է եղել Սարգիս Գրիգորյանի նախկին կինը
The modern periodic table is sometimes expanded into its long or 32-column form by reinstating the footnoted f-block elements into their natural position between the s- and d-blocks. Unlike the 18-column form this arrangement results in «no interruptions in the sequence of increasing atomic numbers». The relationship of the f-block to the other blocks of the periodic table also becomes easier to see. Jensen advocates a form of table with 32 columns on the grounds that the lanthanides and actinides are otherwise relegated in the minds of students as dull, unimportant elements that can be quarantined and ignored. Despite these advantages the 32-column form is generally avoided by editors on account of its undue rectangular ratio compared to a book page ratio, and the familiarity of chemists with the modern form, as introduced by Seaborg.
Periodic table (large cells, 32-column layout)
Tables with different structures
Main article: Alternative periodic tables
Within 100 years of the appearance of Mendeleev’s table in 1869, Edward G. Mazurs had collected an estimated 700 different published versions of the periodic table. As well as numerous rectangular variations, other periodic table formats have been shaped, for example,[n 9] like a circle, cube, cylinder, building, spiral, lemniscate, octagonal prism, pyramid, sphere, or triangle. Such alternatives are often developed to highlight or emphasize chemical or physical properties of the elements that are not as apparent in traditional periodic tables.
Theodor Benfey’s spiral periodic table
A popular alternative structure is that of Otto Theodor Benfey (1960). The elements are arranged in a continuous spiral, with hydrogen at the centre and the transition metals, lanthanides, and actinides occupying peninsulas.
Most periodic tables are two-dimensional; three-dimensional tables are known to as far back as at least 1862 (pre-dating Mendeleev’s two-dimensional table of 1869). More recent examples include Courtines’ Periodic Classification (1925), Wringley’s Lamina System (1949), Giguère’s Periodic helix (1965) and Dufour’s Periodic Tree (1996). Going one further, Stowe’s Physicist’s Periodic Table (1989) has been described as being four-dimensional (having three spatial dimensions and one colour dimension).
The various forms of periodic tables can be thought of as lying on a chemistry–physics continuum. Towards the chemistry end of the continuum can be found, as an example, Rayner-Canham’s «unruly» Inorganic Chemist’s Periodic Table (2002), which emphasizes trends and patterns, and unusual chemical relationships and properties. Near the physics end of the continuum is Janet’s Left-Step Periodic Table (1928). This has a structure that shows a closer connection to the order of electron-shell filling and, by association, quantum mechanics. A somewhat similar approach has been taken by Alper, albeit criticized by Eric Scerri as disregarding the need to display chemical and physical periodicity. Somewhere in the middle of the continuum is the ubiquitous common or standard form of periodic table. This is regarded as better expressing empirical trends in physical state, electrical and thermal conductivity, and oxidation numbers, and other properties easily inferred from traditional techniques of the chemical laboratory. Its popularity is thought to be a result of this layout having a good balance of features in terms of ease of construction and size, and its depiction of atomic order and periodic trends.