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 attempts of alchemists to arrange information on substances, so as to clarify and anticipate the products of their chemical reactions, resulted in early conceptions of chemical elements and the first rudimentary periodic tables.

As the chemical properties of the elements were known to largely repeat themselves according to the periodic law, in 1919 the American chemist Irving Langmuir suggested that this could be explained if the electrons in an atom were connected or clustered in some manner.

The repeating periodicity of the blocks of 2, 6, 10, and 14 elements within sections of the periodic table arises naturally from the total number of electrons which occupy a complete set of s, p, d and f atomic orbitals, respectively.

It is one of only two elements on the periodic table that are known to be liquids at room temperature ( mercury is the other, although caesium, gallium, and rubidium melt just above room temperature ).

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 standard presentation of the chemical elements is in the periodic table, which orders elements by atomic number and groups them by electron configuration.

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

The periodic table of the chemical elements

The properties of the chemical elements are often summarized using the periodic table that organizes the elements by increasing atomic number into rows (" periods ") in which the columns (" groups ") share recurring (" periodic ") physical and chemical properties.

One of the most convenient, and certainly the most traditional presentation of the elements, is in form of periodic table, which groups elements with similar chemical properties ( and usually also similar electronic structures ) together.

The Department's constant fight with the House for money is a polite minuet compared with its periodic bloody engagements with the Senate.

As expected by periodic trends, it is more electronegative than tin or bismuth, and less electronegative than tellurium or arsenic.

As the meter is defined in terms of the second, and the speed of light is constant for all observers, the terrestrial meter appears to change in length compared to the " planetary meter " on a periodic basis.

Evidence of this is the Antarctic Circumpolar Wave, a periodic oscillation that affects the climate of much of the southern hemisphere.

It is a mathematical tool for finding repeating patterns, such as the presence of a periodic signal which has been buried under noise, or identifying the missing fundamental frequency in a signal implied by its harmonic frequencies.

Botswana is affected by periodic droughts, and seasonal August winds blow from the west, carrying sand and dust, which can obscure visibility.

In the periodic table, it is located to the right of the actinide curium, to the left of the actinide californium and below the lanthanide terbium with which it shares many similarities in physical and chemical properties.

In order to win the final cash prize, all the contestants have to do is survive periodic evictions and be the last one standing.

As a member of group 14 on the periodic table, it is nonmetallic and tetravalent — making four electrons available to form covalent chemical bonds.

The periodic arrays of submicrometre spherical particles provide similar arrays of interstitial voids, which act as a natural diffraction grating for visible light waves, particularly when the interstitial spacing is of the same order of magnitude as the incident lightwave.

The electrical part of the heart is centered on the periodic contraction ( squeezing ) of the muscle cells that is caused by the cardiac pacemaker located in the sinoatrial node.

Rainfall is irregular, historically causing periodic droughts and famines.

A more refined classification is often shown in colored presentations of the periodic table ; this system restricts the terms " metal " and " nonmetal " to only certain of the more broadly defined metals and nonmetals, adding additional terms for certain sets of the more broadly viewed metals and nonmetals.