The alkali metals are a group of chemical elements in the periodic table with very similar properties: they are all shiny, soft, silvery, highly reactive metals at standard temperature and pressure and readily lose their outermost electron to form cations with charge + 1.

This group lies in the s-block of the periodic table as all alkali metals have their outermost electron in an s-orbital.

The alkali metals provide the best example of group trends in properties in the periodic table, with elements exhibiting well-characterized homologous behaviour.

The conventional symbol Z comes from the German word meaning number / numeral / figure, which prior to the modern synthesis of ideas from chemistry and physics, merely denoted an element's numerical place in the periodic table.

Loosely speaking, the existence of a periodic table creates an ordering for the elements.

A simple numbering based on periodic table position was never entirely satisfactory.

Besides iodine and tellurium, later several other pairs of elements ( such as argon and potassium, cobalt and nickel ) were known to have nearly identical or reversed atomic weights, leaving their placement in the periodic table by chemical properties to be in violation of known physical properties.

Nevertheless, in spite of Rutherford's estimation that gold had a central charge of about 100 ( but was element Z = 79 on the periodic table ), a month after Rutherford's paper appeared, Antonius van den Broek first formally suggested that the central charge and number of electrons in an atom was exactly equal to its place in the periodic table ( also known as element number, atomic number, and symbolized Z ).

However, prior to 1915, the word Zahl ( simply number ) was used for an element's assigned number in the periodic table.

* History of the periodic table

It is in group 18 ( noble gases ) of the periodic table.

Actinium gave the name to the actinide series, a group of 15 similar elements between actinium and lawrencium in the periodic table.

The group of elements is more diverse than the lanthanides and therefore it was not until 1945 that Glenn T. Seaborg proposed the most significant change to Mendeleev's periodic table, by introducing the actinides.

This transuranic element of the actinide series is located in the periodic table below the lanthanide element europium, and thus by analogy was named after another continent, America.

At the time, the periodic table had been restructured by Seaborg to its present layout, containing the actinide row below the lanthanide one.

Among the first 101 elements in the periodic table, only francium is less stable.

Dmitri Mendeleev | Mendeleev's first periodic table ( 1869 )

In 1869, building upon earlier discoveries by such scientists as Lavoisier, Dmitri Mendeleev published the first functional periodic table.

The table itself is a visual representation of the periodic law, which states that certain chemical properties of elements repeat periodically when arranged by atomic number.

While experimenting with the products of radioactive decay, in 1913 radiochemist Frederick Soddy discovered that there appeared to be more than one type of atom at each position on the periodic table.

These results refined Ernest Rutherford's and Antonius Van den Broek's model, which proposed that the atom contains in its nucleus a number of positive nuclear charges that is equal to its ( atomic ) number in the periodic table.

At this stage, it wasn't clear what atoms were although they could be described and classified by their properties ( in bulk ) in a periodic table.

The discovery of the chemical elements has a long history from the days of alchemy and culminating in the creation of the periodic table of the chemical elements by Dmitri Mendeleev ( 1834 – 1907 ) and later discoveries of some synthetic elements.

The discoveries of the chemical elements has a long history culminating in the creation of the periodic table by Dmitri Mendeleev.

These weights were an important pre-requisite for the discovery of the periodic law by Dmitri Mendeleev and Lothar Meyer.

In 1869, Dmitri Mendeleev predicted its existence and some of its properties based on its position on his periodic table and called the element ekasilicon.

* 1869 – Dmitri Mendeleev presents the first periodic table to the Russian Chemical Society.

In 1902, having accepted the evidence for the elements helium and argon, Dmitri Mendeleev included these noble gases as group 0 in his arrangement of the elements, which would later become the periodic table.

Although precursors exist, the current table is generally credited to Dmitri Mendeleev, who developed it in 1869 to illustrate periodic trends in the properties of the then-known elements ; the layout has been refined and extended as new elements have been discovered and new theoretical models developed to explain chemical behavior.

** 101. mendelevium, Md, named after the Russian chemist Dmitri Mendeleev, credited for being the primary creator of the periodic table of the chemical elements ( 1955 ).

At this stage, it wasn't clear what atoms were-although they could be described and classified by their observable properties in bulk ; summarized by the developing periodic table, by John Newlands and Dmitri Mendeleyev around the mid to late 19th century.

* 1871 Dmitri Ivanovich Mendeleev systematically examines the periodic table and predicts the existence of gallium, scandium, and germanium

The existence of gallium had been predicted during 1871 by Dmitri Mendeleev, who called it eka-aluminium, and its discovery was a boost for Mendeleev's theory of the periodic table.

These careful, accurate atomic weight measurements of Stas helped lay the foundation for the periodic system of elements of Dmitri Mendeleev and others.

* Dmitri Mendeleev Russian chemist, creator of the first periodic table

In 1869, Russian chemist Dmitri Mendeleev published his periodic table, which had empty spaces for elements directly above and under yttrium.

The history of the periodic table reflects over a century of growth in the understanding of chemical properties, and culminates with the publication of the first actual periodic table by Dmitri Mendeleev in 1869.

Dmitri Mendeleev, a Russian chemist, was the first scientist to make a periodic table much like the one we use today.

He was contemporary and competitor of Dmitri Mendeleev to draw up the first periodic table of chemical elements.

Dmitri Mendeleev, responsible for the periodic table.

A great breakthrough in making sense of this long list ( as well as in understanding the internal structure of atoms as discussed below ) was Dmitri Mendeleev and Lothar Meyer's development of the periodic table, and particularly Mendeleev's use of it to predict the existence and the properties of germanium, gallium, and scandium, which Mendeleev called ekasilicon, ekaaluminium, and ekaboron respectively.

Dmitri Mendeleyev, who originated the periodic table of the elements, never received a Nobel Prize.

The final death blow for the use of equivalent weights for the elements was the Dmitri Mendeleev's presentation of his periodic table in 1869, in which he related the chemical properties of the elements to the approximate order of their atomic weights.