Hydrogen

Hydrogen is that the element with the symbol H and no 1. With a typical relative mass of 1.008, hydrogen is that the lightest element within the table. Hydrogen is that the foremost abundant chemical substance within the universe, constituting roughly 75% of all baryonic mass. Non-remnant stars are mainly composed of hydrogen within the plasma state. the foremost common isotope of hydrogen, termed protium (name rarely used, symbol 1H), has one proton and no neutrons.

Hydrogen was discovered by Henry Cavendish in 1766 and named by Antoine Lavoisier in 1783.

Physical properties
Appearance	Colorless Gas
Atomic weight	1.008
Atomic number	1
Group	Group 1: Hydrogen and Alkali metals
Period	Period 1
Block	s-block*
Electron configuration*	1s1
Electrons per shell	1
Phase at STP(Standard Temperature and Pressure)	Gas
Melting point	(H2) 13.99K (−259.16°C, −434.49°F)
Boiling point	(H2) 20.271K (−252.879°C, −423.182°F)
Density at STP when liquid at m.p. (Melting point)	0.08988 g/L 0.07 g/cm3 (solid: 0.0763 g/cm3)
Triple point*	13.8033 K, 7.041 kPa
Critical point*	32.938 K, 1.2858 MPa
The heat of fusion (H2)	0.117 kJ/mol
Heat of vaporization	(H2) 0.904 kJ/mol
Molar heat capacity	(H2) 28.836 J/(mol· K)
Vapor pressure	15K: 10000P 20K: 100000P

Atomic properties
Oxidation states*	−1, +1 (an amphoteric oxide)
Electronegativity*	Pauling scale: 2.20
Ionization energies*	1st: 1312.0 kJ/mol
Covalent radius*	31±5 pm
Van der Waals radius*	120 pm

 

1.  A block of the periodic table is a set of elements unified by the orbitals their valence electrons or vacancies lie in.
2.  The electronic configuration is the arrangement of electrons in energy levels around an atomic nucleus.
3.  The triple point of a substance is the temperature and pressure at which the three phases of that substance coexist in thermodynamic equilibrium.
4.  A critical point is the endpoint of a phase equilibrium curve.
5.  The oxidation state sometimes referred to as oxidation number, describes the degree of oxidation of an atom in a chemical compound.
6.  Electronegativity is the tendency of an atom to attract shared electrons to itself.
7.  In physics and chemistry, ionization energy is the minimum amount of energy required to remove the most loosely bound electron of an isolated neutral gaseous atom or molecule.
8.  The covalent radius is a measure of the size of an atom that forms part of one covalent bond.
9.  The Van der Waals radius of an atom is the radius of an imaginary hard-sphere representing the distance of closest approach for another atom.

Source: Wikipedia