Changes

==Chemical Properties==

==Chemical Properties==

At normal pressures hydrogen melts at 14.01[[Kelvin]] (K) and boils at 20.28K, essentially meaning that it only exists on Earth as a gas. The near-vacuum of interstellar space means that hydrogen is also a gas under these circumstances. Astronomers and chemists hypothesise that hydrogen exists as a plasma inside stars and possibly in a metallic form in the cores of gas giant [[planets]] such as [[Jupiter]]. The most common form of hydrogen is molecular hydrogen, consisting of two atoms bonded by a single hydrogen bond. The chemical symbol for molecular hydrogen is H₂.

At normal pressures hydrogen melts at 14.01[[Kelvin]] (K) and boils at 20.28K, essentially meaning that it only exists on Earth as a gas. The near-vacuum of interstellar space means that hydrogen is also a gas under these circumstances. Astronomers and chemists hypothesise that hydrogen exists as a plasma inside stars and possibly in a metallic form in the cores of gas giant [[planets]] such as [[Jupiter]]. The most common form of hydrogen is molecular hydrogen, consisting of two atoms bonded by a single covalent bond. The chemical symbol for molecular hydrogen is H₂.

Due to having the lowest possible atomic number hydrogen is the lightest element. As a result of this it was used in many early airships and balloons, but due to the dangers involved it has been replaced by [[helium]] in these applications.

Due to having the lowest possible atomic number hydrogen is the lightest element. As a result of this it was used in many early airships and balloons, but due to the dangers involved it has been replaced by [[helium]] in these applications.

==Isotopes==

==Isotopes==

The most common form of hydrogen is protium, although this name is rarely used and it is generally known simply as hydrogen.  Protium [[atom]]s consist of a single [[proton]] orbited by a single [[electron]]. Two other hydrogen [[isotopes]] are known to exist: [[deuterium]], which has one neutron and an atomic weight of 2, and [[tritium]] with two neutrons and an atomic weight of 3. [[Tritium]] is [[radioactive]], with a [[half-life]] of 12.32 years. Naturally occurring tritium is extremely rare on Earth but has a number of valuable applications, such as light-emitting inserts for optical instruments and emergency equipment. As a result it is extremely expensive. {{fact}}

The most common form of hydrogen is protium, although this name is rarely used and it is generally known simply as hydrogen.  Protium [[atom]]s consist of a single [[proton]] orbited by a single [[electron]]. Two other hydrogen [[isotopes]] are known to exist: [[deuterium]], which has one neutron and an atomic weight of 2, and [[tritium]] with two neutrons and an atomic weight of 3. [[Tritium]] is [[radioactive]], with a [[half-life]] of 12.32 years. Naturally occurring tritium is extremely rare on Earth; it is manufactured in nuclear reactors and is therefore extremely expensive.  It has a number of valuable applications, such as light-emitting inserts for optical instruments and emergency equipment.

==Compounds==

==Compounds==

==Occurrence in Nature==

==Occurrence in Nature==

Hydrogen makes up 75% of all matter in the universe by mass. Well over 90% of all atoms in the universe are hydrogen. It is the main element found in [[stars]] and gas-giant (Jovian) planets. Huge clouds of molecular hydrogen are found in interstellar space; most astronomers believe that these clouds are associated with star formation, with the hydrogen providing the raw material and fuel for stars to form. However the timescale required for this to occur is claimed to be around 100,000 years for a star the size of the [[Sun]], which means that the process cannot be observed. For this and other reasons, this hypothesis is generally rejected by Creation scientists.{{fact}}

Hydrogen makes up 75% of all matter in the universe by mass. Well over 90% of all atoms in the universe are hydrogen. It is the main element found in [[stars]] and gas-giant (Jovian) planets. Huge clouds of molecular hydrogen are found in interstellar space; astronomers believe that these clouds are associated with star formation, with the hydrogen providing the raw material and fuel for stars to form. The timescale required for this to occur is estimated to be around 100,000 years for a star the size of the [[Sun]].  This means that, like other cosmic processes, some of which take millions or billions of years, the process of star formation cannot be observed directly. However, stars in various phases of the process are abundant, and the process is well established.  Young-Universe Creationists reject all of this.

==Fuel for vehicles==

==Fuel for vehicles==