The Element Hydrogen: Simplest Element in the Universe
The element Hydrogen is the simplest and most abundant element in the universe. The most common form consists of only one proton and one electron. It has an electron configuration of 1s1 in its ground state.

Other Isotopes of HydrogenHydrogen has two other known isotopes, or structural forms. Deuterium has one proton and one neutron in its nucleus. Tritium has one proton and two neutrons in its nucleus. Both these isotopes have identical chemical properties to Hydrogen. They differ in that they have higher atomic masses and are radioactive. The radioactivity is due to the instability of the larger nuclei of these isotopes. When the nucleus breaks apart energy is released and radiates out from the atom.
Chemical Bonding of Hydrogen
The 1s subshell is the only subshell in the first shell of all atoms. The first shell can only accommodate a maximum of two electrons, and so in order to gain a full outer shell (1s2), hydrogen commonly forms single covalent (sharing) bonds with other elements. Consider the electron dot diagram for the element hydrogen, where the large sphere represents whole of the atom except the outer shell electron.
We can put two Hydrogen atoms together and when they share their electrons, each now has a full outer shell of two electrons.
We can apply the came process to Hydrogen bonding with other elements. Carbon has four outer shell electrons and requires eight for maximum stability. We can match up four hydrogen atoms with carbon since each Hydrogen can provide Carbon with one of the missing electrons.

Once we move the Hydrogens around in order to line up pairs of electrons we can see that Carbon will bond with four Hydrogen atoms, as shown below. In this example both the Carbon atom and all four Hydrogen atoms now have full outer shells. This is methane (CH4), a gas commonly associated with oil deposits.

Hydrogen as a MetalAll other elements that have one electron in their outer shells are classified as metals since they readily lose that electron and therefore have an excess of electrons in pure for which allows the element to conduct electricity and gives it the shiny appearance we associate with metals. The element Hydrogen is not considered a metal though as once it has lost its electron it is just a proton and is not considered an atom any more. It is highly likely that the core of the planet Jupiter is composed of liquid metallic hydrogen, a situation that could only arise from the incredible pressure generated by the mass of that planet.
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