A report on Helium and Atom

Spectral lines of helium
Atoms and molecules as depicted in John Dalton's A New System of Chemical Philosophy vol. 1 (1808)
Sir William Ramsay, the discoverer of terrestrial helium
The Geiger–Marsden experiment:
Left: Expected results: alpha particles passing through the plum pudding model of the atom with negligible deflection.
Right: Observed results: a small portion of the particles were deflected by the concentrated positive charge of the nucleus.
The cleveite sample from which Ramsay first purified helium
The Bohr model of the atom, with an electron making instantaneous "quantum leaps" from one orbit to another with gain or loss of energy. This model of electrons in orbits is obsolete.
Historical marker, denoting a massive helium find near Dexter, Kansas
The binding energy needed for a nucleon to escape the nucleus, for various isotopes
The helium atom. Depicted are the nucleus (pink) and the electron cloud distribution (black). The nucleus (upper right) in helium-4 is in reality spherically symmetric and closely resembles the electron cloud, although for more complicated nuclei this is not always the case.
A potential well, showing, according to classical mechanics, the minimum energy V(x) needed to reach each position x. Classically, a particle with energy E is constrained to a range of positions between x1 and x2.
Binding energy per nucleon of common isotopes. The binding energy per particle of helium-4 is significantly larger than all nearby nuclides.
3D views of some hydrogen-like atomic orbitals showing probability density and phase (g orbitals and higher are not shown)
Helium discharge tube shaped like the element's atomic symbol
This diagram shows the half-life (T½) of various isotopes with Z protons and N neutrons.
Liquefied helium. This helium is not only liquid, but has been cooled to the point of superfluidity. The drop of liquid at the bottom of the glass represents helium spontaneously escaping from the container over the side, to empty out of the container. The energy to drive this process is supplied by the potential energy of the falling helium.
These electron's energy levels (not to scale) are sufficient for ground states of atoms up to cadmium (5s2 4d10) inclusively. Do not forget that even the top of the diagram is lower than an unbound electron state.
Unlike ordinary liquids, helium II will creep along surfaces in order to reach an equal level; after a short while, the levels in the two containers will equalize. The Rollin film also covers the interior of the larger container; if it were not sealed, the helium II would creep out and escape.
An example of absorption lines in a spectrum
Structure of the helium hydride ion, HHe+
Graphic illustrating the formation of a Bose–Einstein condensate
Structure of the suspected fluoroheliate anion, OHeF−
Scanning tunneling microscope image showing the individual atoms making up this gold (100) surface. The surface atoms deviate from the bulk crystal structure and arrange in columns several atoms wide with pits between them (See surface reconstruction).
The largest single use of liquid helium is to cool the superconducting magnets in modern MRI scanners.
Periodic table showing the origin of each element. Elements from carbon up to sulfur may be made in small stars by the alpha process. Elements beyond iron are made in large stars with slow neutron capture (s-process). Elements heavier than iron may be made in neutron star mergers or supernovae after the r-process.
A dual chamber helium leak detection machine
Because of its low density and incombustibility, helium is the gas of choice to fill airships such as the Goodyear blimp.

In the perspective of quantum mechanics, helium is the second simplest atom to model, following the hydrogen atom.

- Helium

Helium was discovered in this way in the spectrum of the Sun 23 years before it was found on Earth.

- Atom
Spectral lines of helium

18 related topics with Alpha

Overall

The chemical elements ordered in the periodic table

Chemical element

8 links

The chemical elements ordered in the periodic table
Estimated distribution of dark matter and dark energy in the universe. Only the fraction of the mass and energy in the universe labeled "atoms" is composed of chemical elements.
Periodic table showing the cosmogenic origin of each element in the Big Bang, or in large or small stars. Small stars can produce certain elements up to sulfur, by the alpha process. Supernovae are needed to produce "heavy" elements (those beyond iron and nickel) rapidly by neutron buildup, in the r-process. Certain large stars slowly produce other elements heavier than iron, in the s-process; these may then be blown into space in the off-gassing of planetary nebulae
Abundances of the chemical elements in the Solar System. Hydrogen and helium are most common, from the Big Bang. The next three elements (Li, Be, B) are rare because they are poorly synthesized in the Big Bang and also in stars. The two general trends in the remaining stellar-produced elements are: (1) an alternation of abundance in elements as they have even or odd atomic numbers (the Oddo-Harkins rule), and (2) a general decrease in abundance as elements become heavier. Iron is especially common because it represents the minimum energy nuclide that can be made by fusion of helium in supernovae.
Mendeleev's 1869 periodic table: An experiment on a system of elements. Based on their atomic weights and chemical similarities.
Dmitri Mendeleev
Henry Moseley

A chemical element is a species of atoms that have a given number of protons in their nuclei, including the pure substance consisting only of that species.

The lightest chemical elements are hydrogen and helium, both created by Big Bang nucleosynthesis during the first 20 minutes of the universe in a ratio of around 3:1 by mass (or 12:1 by number of atoms), along with tiny traces of the next two elements, lithium and beryllium.

The Space Shuttle Main Engine burnt hydrogen with oxygen, producing a nearly invisible flame at full thrust.

Hydrogen

7 links

Chemical element with the symbol H and atomic number 1.

Chemical element with the symbol H and atomic number 1.

The Space Shuttle Main Engine burnt hydrogen with oxygen, producing a nearly invisible flame at full thrust.
Depiction of a hydrogen atom with size of central proton shown, and the atomic diameter shown as about twice the Bohr model radius (image not to scale)
Hydrogen gas is colorless and transparent, here contained in a glass ampoule.
Phase diagram of hydrogen. The temperature and pressure scales are logarithmic, so one unit corresponds to a 10x change. The left edge corresponds to 105 Pa, which is about atmospheric pressure.
A sample of sodium hydride
Hydrogen discharge (spectrum) tube
Deuterium discharge (spectrum) tube
Antoine-Laurent de Lavoisier
Hydrogen emission spectrum lines in the visible range. These are the four visible lines of the Balmer series
NGC 604, a giant region of ionized hydrogen in the Triangulum Galaxy
300x300px
300x300px
360x360px

For the most common isotope of hydrogen (symbol 1H) each atom has one proton, one electron, and no neutrons.

Regular passenger service resumed in the 1920s and the discovery of helium reserves in the United States promised increased safety, but the U.S. government refused to sell the gas for this purpose.

Helium was first detected in the Sun due to its characteristic spectral lines.

Noble gas

5 links

The noble gases (historically also the inert gases; sometimes referred to as aerogens ) make up a class of chemical elements with similar properties; under standard conditions, they are all odorless, colorless, monatomic gases with very low chemical reactivity.

The noble gases (historically also the inert gases; sometimes referred to as aerogens ) make up a class of chemical elements with similar properties; under standard conditions, they are all odorless, colorless, monatomic gases with very low chemical reactivity.

Helium was first detected in the Sun due to its characteristic spectral lines.
This is a plot of ionization potential versus atomic number. The noble gases, which are labeled, have the largest ionization potential for each period.
Neon, like all noble gases, has a full valence shell. Noble gases have eight electrons in their outermost shell, except in the case of helium, which has two.
Structure of, one of the first noble gas compounds to be discovered
An endohedral fullerene compound containing a noble gas atom
Bonding in according to the 3-center-4-electron bond model
Liquid helium is used to cool superconducting magnets in modern MRI scanners
Goodyear Blimp
15,000-watt xenon short-arc lamp used in IMAX projectors

The six naturally occurring noble gases are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and the radioactive radon (Rn).

The properties of the noble gases can be well explained by modern theories of atomic structure: Their outer shell of valence electrons is considered to be "full", giving them little tendency to participate in chemical reactions, and it has been possible to prepare only a few hundred noble gas compounds.

Drifting smoke particles indicate the movement of the surrounding gas.

Gas

4 links

One of the four fundamental states of matter .

One of the four fundamental states of matter .

Drifting smoke particles indicate the movement of the surrounding gas.
Shuttle imagery of re-entry phase
184x184px
Random motion of gas particles results in diffusion.
21 April 1990 eruption of Mount Redoubt, Alaska, illustrating real gases not in thermodynamic equilibrium.
Boyle's equipment
Dalton's notation.
Compressibility factors for air.
Satellite view of weather pattern in vicinity of Robinson Crusoe Islands on 15 September 1999, shows a turbulent cloud pattern called a Kármán vortex street
Delta wing in wind tunnel. The shadows form as the indices of refraction change within the gas as it compresses on the leading edge of this wing.

A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or compound molecules made from a variety of atoms (e.g. carbon dioxide).

When grouped together with the monatomic noble gases – helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn) – these gases are referred to as "elemental gases".

435x435px

Periodic table

4 links

Tabular display of the chemical elements.

Tabular display of the chemical elements.

435x435px
3D views of some hydrogen-like atomic orbitals showing probability density and phase (g orbitals and higher are not shown)
Idealized order of shell-filling (most accurate for n  ≲ 4.)
Trend in atomic radii
Graph of first ionisation energies of the elements in electronvolts (predictions used for elements 105–118)
Trend in electron affinities
Flowing liquid mercury. Its liquid state at room temperature is a result of special relativity.
A periodic table colour-coded to show some commonly used sets of similar elements. The categories and their boundaries differ somewhat between sources. Alkali metals
 Alkaline earth metals
 Lanthanides
 Actinides
 Transition metals Other metals
 Metalloids
 Other nonmetals
 Halogens
 Noble gases
Mendeleev's 1869 periodic table
Mendeleev's 1871 periodic table
Dmitri Mendeleev
Henry Moseley
Periodic table of van den Broek
Glenn T. Seaborg
One possible form of the extended periodic table to element 172, suggested by Finnish chemist Pekka Pyykkö. Deviations from the Madelung order (8s < < 6f < 7d < 8p) begin to appear at elements 139 and 140, though for the most part it continues to hold approximately.
Otto Theodor Benfey's spiral periodic table (1964)
Iron, a metal
Sulfur, a nonmetal
Arsenic, an element often called a semi-metal or metalloid

The smallest constituents of all normal matter are known as atoms.

Hydrogen is the element with atomic number 1; helium, atomic number 2; lithium, atomic number 3; and so on.

Atomic orbitals of the electron in a hydrogen atom at different energy levels. The probability of finding the electron is given by the color, as shown in the key at upper right.

Atomic orbital

5 links

Domain coloring of a

Domain coloring of a

Atomic orbitals of the electron in a hydrogen atom at different energy levels. The probability of finding the electron is given by the color, as shown in the key at upper right.
3D views of some hydrogen-like atomic orbitals showing probability density and phase (g orbitals and higher are not shown)
The Rutherford–Bohr model of the hydrogen atom.
Energetic levels and sublevels of polyelectronic atoms.
Experimentally imaged 1s and 2p core-electron orbitals of Sr, including the effects of atomic thermal vibrations and excitation broadening, retrieved from energy dispersive x-ray spectroscopy (EDX) in scanning transmission electron microscopy (STEM).
The 1s, 2s, and 2p orbitals of a sodium atom.
Atomic orbitals spdf m-eigenstates and superpositions
Electron atomic and molecular orbitals. The chart of orbitals (left) is arranged by increasing energy (see Madelung rule). Note that atomic orbits are functions of three variables (two angles, and the distance r from the nucleus). These images are faithful to the angular component of the orbital, but not entirely representative of the orbital as a whole.
Drum mode <math>u_{01}</math>
Drum mode <math>u_{02}</math>
Drum mode <math>u_{03}</math>
Wave function of 1s orbital (real part, 2D-cut, <math>r_{max}=2 a_0</math>)
Wave function of 2s orbital (real part, 2D-cut, <math>r_{max}=10 a_0</math>)
Wave function of 3s orbital (real part, 2D-cut, <math>r_{max}=20 a_0</math>)
Drum mode <math>u_{11}</math>
Drum mode <math>u_{12}</math>
Drum mode <math>u_{13}</math>
Wave function of 2p orbital (real part, 2D-cut, <math>r_{max}=10 a_0</math>)
Wave function of 3p orbital (real part, 2D-cut, <math>r_{max}=20 a_0</math>)
Wave function of 4p orbital (real part, 2D-cut, <math>r_{max}=25 a_0</math>)
Drum mode <math>u_{21}</math>
Drum mode <math>u_{22}</math>
Drum mode <math>u_{23}</math>

In atomic theory and quantum mechanics, an atomic orbital is a function describing the location and wave-like behavior of an electron in an atom.

However, this did not explain similarities between different atoms, as expressed by the periodic table, such as the fact that helium (two electrons), neon (10 electrons), and argon (18 electrons) exhibit similar chemical inertness.

Wave functions of the electron in a hydrogen atom at different energy levels. Quantum mechanics cannot predict the exact location of a particle in space, only the probability of finding it at different locations. The brighter areas represent a higher probability of finding the electron.

Quantum mechanics

3 links

Wave functions of the electron in a hydrogen atom at different energy levels. Quantum mechanics cannot predict the exact location of a particle in space, only the probability of finding it at different locations. The brighter areas represent a higher probability of finding the electron.
Fig. 1
Position space probability density of a Gaussian wave packet moving in one dimension in free space.
1-dimensional potential energy box (or infinite potential well)
Some trajectories of a harmonic oscillator (i.e. a ball attached to a spring) in classical mechanics (A-B) and quantum mechanics (C-H). In quantum mechanics, the position of the ball is represented by a wave (called the wave function), with the real part shown in blue and the imaginary part shown in red. Some of the trajectories (such as C, D, E, and F) are standing waves (or "stationary states"). Each standing-wave frequency is proportional to a possible energy level of the oscillator. This "energy quantization" does not occur in classical physics, where the oscillator can have any energy.
Schematic of a Mach–Zehnder interferometer.
Max Planck is considered the father of the quantum theory.
The 1927 Solvay Conference in Brussels was the fifth world physics conference.

Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles.

Even the helium atom – which contains just two electrons – has defied all attempts at a fully analytic treatment.

Bohr in 1922

Niels Bohr

3 links

Bohr in 1922
Bohr as a young man
Bohr and Margrethe Nørlund on their engagement in 1910.
The Bohr model of the hydrogen atom. A negatively charged electron, confined to an atomic orbital, orbits a small, positively charged nucleus; a quantum jump between orbits is accompanied by an emitted or absorbed amount of electromagnetic radiation.
The evolution of atomic models in the 20th century: Thomson, Rutherford, Bohr, Heisenberg/Schrödinger
The Niels Bohr Institute, part of the University of Copenhagen
Bohr and Albert Einstein (image from 1925) had a long-running debate about the metaphysical implication of quantum physics.
Werner Heisenberg (left) with Bohr at the Copenhagen Conference in 1934
Bohr with James Franck, Albert Einstein and Isidor Isaac Rabi (LR)
Bohr's coat of arms, 1947. Argent, a taijitu (yin-yang symbol) Gules and Sable. Motto: Contraria sunt complementa ("opposites are complementary").
The Theory of Spectra and Atomic Constitution (Drei Aufsätze über Spektren und Atombau), 1922

Niels Henrik David Bohr (7 October 1885 – 18 November 1962) was a Danish physicist who made foundational contributions to understanding atomic structure and quantum theory, for which he received the Nobel Prize in Physics in 1922.

When challenged on this by Alfred Fowler, Bohr replied that they were caused by ionised helium, helium atoms with only one electron.

The cake 
model of the hydrogen atom or a hydrogen-like ion (Z > 1), where the negatively charged electron confined to an atomic shell encircles a small, positively charged atomic nucleus and where an electron jumps between orbits, is accompanied by an emitted or absorbed amount of electromagnetic energy (h&nu;). The orbits in which the electron may travel are shown as grey circles; their radius increases as n2, where n is the principal quantum number. The 3 &rarr; 2 transition depicted here produces the first line of the Balmer series, and for hydrogen  it results in a photon of wavelength 656 nm (red light).

Bohr model

3 links

System consisting of a small, dense nucleus surrounded by orbiting electrons—similar to the structure of the Solar System, but with attraction provided by electrostatic forces in place of gravity.

System consisting of a small, dense nucleus surrounded by orbiting electrons—similar to the structure of the Solar System, but with attraction provided by electrostatic forces in place of gravity.

The cake 
model of the hydrogen atom or a hydrogen-like ion (Z > 1), where the negatively charged electron confined to an atomic shell encircles a small, positively charged atomic nucleus and where an electron jumps between orbits, is accompanied by an emitted or absorbed amount of electromagnetic energy (h&nu;). The orbits in which the electron may travel are shown as grey circles; their radius increases as n2, where n is the principal quantum number. The 3 &rarr; 2 transition depicted here produces the first line of the Balmer series, and for hydrogen  it results in a photon of wavelength 656 nm (red light).
Bohr model in 1921 after Sommerfeld expansion of 1913 model showing maximum electrons per shell with shells labeled in X-ray notation
Models depicting electron energy levels in hydrogen, helium, lithium, and neon
Elliptical orbits with the same energy and quantized angular momentum

However, because of its simplicity, and its correct results for selected systems (see below for application), the Bohr model is still commonly taught to introduce students to quantum mechanics or energy level diagrams before moving on to the more accurate, but more complex, valence shell atom.

This not only involves one-electron systems such as the hydrogen atom, singly ionized helium, and doubly ionized lithium, but it includes positronium and Rydberg states of any atom where one electron is far away from everything else.

Timeline of the metric expansion of space, where space, including hypothetical non-observable portions of the universe, is represented at each time by the circular sections. On the left, the dramatic expansion occurs in the inflationary epoch; and at the center, the expansion accelerates (artist's concept; not to scale).

Big Bang

3 links

Initial state of high density and temperature.

Initial state of high density and temperature.

Timeline of the metric expansion of space, where space, including hypothetical non-observable portions of the universe, is represented at each time by the circular sections. On the left, the dramatic expansion occurs in the inflationary epoch; and at the center, the expansion accelerates (artist's concept; not to scale).
Panoramic view of the entire near-infrared sky reveals the distribution of galaxies beyond the Milky Way. Galaxies are color-coded by redshift.
Artist's depiction of the WMAP satellite gathering data to help scientists understand the Big Bang
Abell 2744 galaxy cluster – Hubble Frontier Fields view.
The cosmic microwave background spectrum measured by the FIRAS instrument on the COBE satellite is the most-precisely measured blackbody spectrum in nature. The data points and error bars on this graph are obscured by the theoretical curve.
9 year WMAP image of the cosmic microwave background radiation (2012). The radiation is isotropic to roughly one part in 100,000.
Focal plane of BICEP2 telescope under a microscope - used to search for polarization in the CMB.
Chart shows the proportion of different components of the universe – about 95% is dark matter and dark energy.
The overall geometry of the universe is determined by whether the Omega cosmological parameter is less than, equal to or greater than 1. Shown from top to bottom are a closed universe with positive curvature, a hyperbolic universe with negative curvature and a flat universe with zero curvature.

After its initial expansion, an event that is by itself often called "the Big Bang", the universe cooled sufficiently to allow the formation of subatomic particles, and later atoms.

Giant clouds of these primordial elements—mostly hydrogen, with some helium and lithium—later coalesced through gravity, forming early stars and galaxies, the descendants of which are visible today.