Hydrogen is a chemical element with chemical symbol H and atomic number 1. With an atomic weight of 1.00794 u, hydrogen is the lightest element on the periodic table. Its monatomic form (H) is the most abundant chemical substance in the Universe, constituting roughly 75% of all baryonic mass.
Read key information and facts about element Hydrogen
|Group in Periodic Table||1|
|Group Name||lithium family|
|Period in Periodic Table||1|
|Block in Periodic Table||s-block|
|Melting Point||-259.14 °C|
|Boiling Point||-252.87 °C|
|Electronic Shell Structure|||
Periodic table is arranged by atomic number, number of protons in the nucleus which is same as number of electrons. The atomic number increases from left to right. Periodic table starts at top left ( Atomic number 1) and ends at bottom right (atomic number 118). Therefore you can directly look for atomic number 1 to find Hydrogen on periodic table.
Another way to read periodic table and locate an element is by using group number (column) and period number (row). To locate Hydrogen on periodic table look for cross section of group 1 and period 1 in the modern periodic table.
The element Hydrogen was discovered by Henry Cavendish in year 1766 in United Kingdom . Hydrogen derived its name from the Greek elements hydro- and -gen meaning 'water-forming'
The table below shows the abundance of Hydrogen in Universe, Sun, Meteorites, Earth's Crust, Oceans and Human Body.
|Ppb by weight (1ppb =10^-7 %)|
|Abundance in Universe||0.75|
|Abundance in Sun||0.75|
|Abundance in Meteorites||0.024|
|Abundance in Earth's Crust||0.0015|
|Abundance in Oceans||0.11|
|Abundance in Humans||0.1|
The solid state structure of Hydrogen is Simple Hexagonal.
The Crystal structure can be described in terms of its unit Cell. The unit Cells repeats itself in three dimensional space to form the structure.
The unit cell is represented in terms of its lattice parameters, which are the lengths of the cell edges Lattice Constants (a, b and c)
|470 pm||470 pm||340 pm|
and the angles between them Lattice Angles (alpha, beta and gamma).
The positions of the atoms inside the unit cell are described by the set of atomic positions ( xi, yi, zi) measured from a reference lattice point.
The symmetry properties of the crystal are described by the concept of space groups. All possible symmetric arrangements of particles in three-dimensional space are described by the 230 space groups (219 distinct types, or 230 if chiral copies are considered distinct.
|Space Group Name||P63/mmc|
|Space Group Number||194|
|Crystal Structure||Simple Hexagonal|
Hydrogen atoms have 1 electrons and the electronic shell structure is  with Atomic Term Symbol (Quantum Numbers) 2S1/2.
|Number of Electrons (with no charge)||1|
|Number of Protons||1|
|Number of Neutrons||0|
|Shell structure (Electrons per energy level)|||
|Atomic Term Symbol (Quantum Numbers)||2S1/2|
Shell Structure of Hydrogen - Electrons per energy level
The ground state electronic configuration of Neutral Hydrogen atom is 1s1. The portion of Hydrogen configuration that is equivalent to the noble gas of the preceding period, is abbreviated as 1s1]. For atoms with many electrons, this notation can become lengthy and so an abbreviated notation is used.This is important as it is the Valence electrons 1s1, electrons in the outermost shell that determine the chemical properties of the element.
Complete ground state electronic configuration for the Hydrogen atom, Unabbreviated electronic configuration
Hydrogen atomic radius is 53 pm, while it's covalent radius is 37 pm.
53 pm (0.53 Å)
|Atomic Volume||11.2117908788 cm3|
|Covalent Radius||37 pm (0.37 Å)|
|Van der Waals Radius||120 pm|
|Neutron Cross Section||0.332 σa/barns|
The electron affinity of Hydrogen is 72.8 kJ/mol
Refer to table below for Ionization energies of Hydrogen
|Ionization energy number||Enthalpy - kJ/mol|
Refer to below table for Hydrogen Physical Properties
|Molar Volume||11.2117908788 cm3|
Hydrogen is N/A of electricity. Refer to table below for the Electrical properties of Hydrogen
|Thermal Conductivity||0.1805 W/(m K)|
|Mass Magnetic Susceptibility||-2.48×10-8|
|Molar Magnetic Susceptibility||-4.999×10-11|
|Volume Magnetic Susceptibility||-2.23×10-9|
|Speed of Sound||1270 m/s|
Refer to table below for Thermal properties of Hydrogen
|Melting Point||14.01 K (-259.14 °C)|
|Boiling Point||20.28 K (-252.87 °C)|
|Critical Temperature||32.97 K|
|Heat of Fusion||0.558 kJ/mol|
|Heat of Vaporization||0.452 kJ/mol|
|Heat of Combustion||N/A|
Isotopes of rhodium. Naturally occurring Hydrogen has 2 stable isotope - 1H, 2H.
|Isotope||Isotope Mass||% Abundance||T half||Decay Mode|
|DOT Hazard Class||2.1|
|NFPA Fire Rating||4|
|NFPA Health Rating||3|
|NFPA Reactivity Rating||0|
|Autoignition Point||535.5 °C|
List of unique identifiers to search the element in various chemical registry databases
|CAS Number - Chemical Abstracts Service (CAS)||CAS1333-74-0|
|Alkali Metals||Alkaline Earth Metals|
|Transition Metals||Post-Transition Metals|