Hydrogen, of course. On some periodic tables you still see it in the alkali position and heading the halogen column to.
Hydrogen
You think probable to hydrogen.
hydrogen
Hydrogen
Although hydrogen is written above the alkali metals on the periodic table, it is not an alkali metal. It is only placed in that location because it has 1 electron in its outermost s orbital, like the alkali metals. Some tables put hydrogen all by itself above the rest of the table in the middle, with lines running from it diagonally down to both lithium and fluorine, to indicate its ability to either accept or donate a single electron to achieve a filled outer shell. However, it doesn't really belong with the alkali metals or with the halogens.
Alkali metals are the most reactive group of metals because they have one valence electron that they readily donate to achieve a stable electron configuration. This makes them highly reactive with other elements, especially water and oxygen. They react vigorously, often producing heat and releasing hydrogen gas.
All atoms want to do is make their valence shell full. In alkali metals they have all of their shells completely full except one valence electron. The alkali metals REALLY want to get rid of that electron, so they will react with many elements/compounds to get rid of that electron. In alkaline earth metals they have all of their shells completely full except for two valence electrons. They also want to get rid of those electrons but the alkaline earth metals are not as desperate to do so as the alkali earth metals which make the alkaline much less reactive than the alkali metals.
All atoms want to do is make their valence shell full. In alkali metals they have all of their shells completely full except one valence electron. The alkali metals REALLY want to get rid of that electron, so they will react with many elements/compounds to get rid of that electron. In alkaline earth metals they have all of their shells completely full except for two valence electrons. They also want to get rid of those electrons but the alkaline earth metals are not as desperate to do so as the alkali earth metals which make the alkaline much less reactive than the alkali metals.
the alkali metals have one valence electron, or one electron available to bond with another particle. this lets them bond easily with, lets say, a halogen, which has one 'slot' for an electron. two atoms of an alkali metal would be able to bond with a chalcogen, and so on. it's really all in the number of electrons. the alkaline earth metals have two valence electrons, so they would bond less easily with other elements.
Hydrogen, it is one of the most difficult elements to classify: it can form +1 ions like the alkali metals, it can form -1 ions like the halogens, it is a nonmetal.
maybe a dust that is really strong.
The members of the Group 1 family of elements are: hydrogen, lithium, sodium, potassium, rubidium, caesium and francium. These are the alkali metals (except hydrogen, which is a Group 1 element but isn't really a metal). A link is provided to the Wikipedia article on Group 1 elements. Note that each chemical symbol on the part of the chart is actually a link to the Wikipedia article on that praticular element.