# Hydrogen Definition and 62 Discussions

Hydrogen is the chemical element with the symbol H and atomic number 1. With a standard atomic weight of 1.008, hydrogen is the lightest element in the periodic table. Hydrogen is the most abundant chemical substance in the universe, constituting roughly 75% of all baryonic mass. Non-remnant stars are mainly composed of hydrogen in the plasma state. The most common isotope of hydrogen, termed protium (name rarely used, symbol 1H), has one proton and no neutrons.
The universal emergence of atomic hydrogen first occurred during the recombination epoch (Big Bang). At standard temperature and pressure, hydrogen is a colorless, odorless, tasteless, non-toxic, nonmetallic, highly combustible diatomic gas with the molecular formula H2. Since hydrogen readily forms covalent compounds with most nonmetallic elements, most of the hydrogen on Earth exists in molecular forms such as water or organic compounds. Hydrogen plays a particularly important role in acid–base reactions because most acid-base reactions involve the exchange of protons between soluble molecules. In ionic compounds, hydrogen can take the form of a negative charge (i.e., anion) when it is known as a hydride, or as a positively charged (i.e., cation) species denoted by the symbol H+. The hydrogen cation is written as though composed of a bare proton, but in reality, hydrogen cations in ionic compounds are always more complex. As the only neutral atom for which the Schrödinger equation can be solved analytically, study of the energetics and bonding of the hydrogen atom has played a key role in the development of quantum mechanics.
Hydrogen gas was first artificially produced in the early 16th century by the reaction of acids on metals. In 1766–81, Henry Cavendish was the first to recognize that hydrogen gas was a discrete substance, and that it produces water when burned, the property for which it was later named: in Greek, hydrogen means "water-former".
Industrial production is mainly from steam reforming natural gas, and less often from more energy-intensive methods such as the electrolysis of water. Most hydrogen is used near the site of its production, the two largest uses being fossil fuel processing (e.g., hydrocracking) and ammonia production, mostly for the fertilizer market. Hydrogen is problematic in metallurgy because it can embrittle many metals, complicating the design of pipelines and storage tanks.

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1. ### I Partition function rotation

Hey, I have a question about proving Saha's equation for ionizing hydrogen atoms. The formula is \frac{P_{p}}{P_{H}} = \frac{k_{B} T}{P_{e}} \left(\frac{2\pi m_{e} k_{B}T}{h^2} \right)^{\frac{3}{2}}e^{\frac{-I}{k_{B} T}} with P_{p} pressure proton's, P_{H} pressure hydrogen atoms, m_{e}...

I was wondering how they measured or calculated these differences? I dont know what they refer to, but assume theyre scattering Hydrogen with Tritium or Deuterium to measure the difference of something. https://physics.nist.gov/cgi-bin/cuu/Results?search_for=shielding+difference
3. ### I Solving Schrödinger's equation for a hydrogen atom with Euler's method

Hi, first-time poster here I'm a student at HS-level in DK, who has decided to write my annual large scale assignment on Schrödinger's equation. My teacher has only given us a brief introduction to the equation and has tasked us to solve it numerically with Euler's method for the hydrogen atom...
4. ### Why is this water turning black during electrolysis?

Good day, I am here because I have begun a new hobby and it is my hope to better understand what it is I am doing and seeing. Luckily I have the mental capacity to process much of what I read, but sadly I am vastly under-educated. My new project involves electrolysis and for reasons I don't...
5. ### B Fusion of Hydrogen Isotopes

Hi, Does a T-D or a D-D fusion release more energy? Even if D-D needs higher temperatures, would it produce more energy in a fusion reactor?
6. ### B Spectral Line of Hydrogen

If the spectral line of Hydrogen contains four colors, I don’t understand how the electron can jump four times to four different energy levels in the same moment?
7. ### A Grotrian diagram of Hydrogen

Why is it that in Grotrian diagram only the 4p->3s is not allowed, but the 4s->3p, 4p-> 3d and 4d-> 3p are allowed ? I'm following the rules of Δl=±1 and Δm=0,±1 and they give the same numbers. I also tried with Δj=0,±1 and still the same. Grotrian Diagram for Hydrogen for n=[1,4]...
8. ### I 3p->2s: Why spectral line split into three lines in m. field

Hello, suppose we have an excited hydrogen atom in 3p state which makes a transition to 2s state. Then the atom loses some energy by emitting a photon which can be detected (or seen). I have no problems with that situation. If there is an external magnetic field, the energy levels of the...
9. ### Boiling point and connection distance of the elements

Homework Statement Explain the following order of the boiling point (° C) HF (19.5)> HCl (-85.1) <HBr (-66.8) <HI (-35.4) b) Explain the following order of connection distance (pm): HF (92) <HCl (127) <HBr (141) <HI (161) Homework Equations xxx The Attempt at a Solution a) HF does hydrogen...
10. ### Separating hydrogen from effluent HHO by gravity.

I'm would like to learn of the practicality of separating HHO gas released from a photovoltaic charged lead-acid battery bank for hydrogen storage, perhaps by exploiting the substantial difference in density of the two elemental gases. It occurred to me that were the gas emitted from batteries...
11. ### Diagram of energy levels of hydrogen lines

Homework Statement a) Draw a diagram of energy levels to explain the spectrum of lines of the hydrogen atom b) Indicate, for each photon, that its region can be emitted to the electromagnetic spectrum. c) Compare, in a graph, the energies of the orbital of the hydrogen atom with the energies of...
12. ### Automotive Hydrogen Car Fuel Tank

How do hydrogen powered cars prevent the permeation of hydrogen through the valve used to fill the car's tank with hydrogen? Is a regular check valve used or is the valve special in some way?
13. ### Organic Chemistry, Hydrocarbons

Homework Statement Homework Equations The Attempt at a Solution C=C double bonds means that it is not an Alkane because an Alkane is saturated hydrocarbon. So the answer should be from A, B or C.
14. ### Is the world really better off without hydrogen airships?

An airship is any powered, steerable aircraft that it is inflated with a gas that is lighter than air. Hydrogen isn't the only gas usable for airships, but it is the only gas that really makes sense. That is because it has good lift to volume, is relatively inexpensive and is common as dirt...
15. ### Lifting a Man with 100m^3 of Helium

Hi, Reading about different ways to lift a human being, i've come to realise the easiest is simply manipulating density as follows: Denisty of Air at STP: 1.20 kg/m^3 Density of He at STP: 0.000179 kg/m^3 Therefore for every cubic metre (m^3) of air displacement, lift achieved is ~1.2 kg/m^3...
16. ### Measure ionization energy (Hydrogen/Deuterium)

Just wondering if there's any accurate method for direct measurement of the ionization energy of atomic Hydrogen and/or Deuterium ? There's lots of measurements on transitions between various hydrogen/deuterium energy levels but not (it seems) to the limit where n = infinity. Alternatively...
17. ### I Ground State Lamb Shift

What exactly is the so-called "Ground State Lamb Shift". It seems to have been an 'in vogue' quantity up till 1995 or so - then vanished from the literature ?? It's the 'self energy' or something like that of an electron in H 1S orbital. A scientist (at NIST) told me it's a term that has gone...
18. ### Can you separate hydrogen and oxygen molecules?

Is separating hydrogen and oxygen molecules possible? If so, how?
19. ### Is there a material or an element that can repel hydrogen?

I’m working on an idea that I have, and I was wondering if there was something that could repel hydrogen. Not water, not oxygen, just hydrogen. Thanks!
20. S

### Bohr orbit (extremely confused)

Homework Statement Calculate energy of electron in first excited state of hydrogen atom. Homework Equations n=2 when i use E=-13.6 (z/n)^2 and then use E=hc/lamda(wavelength) then wavelength is coming wrong The Attempt at a Solution the correct answer is 6.68 armstrong.

27. ### B Why only certain colors in emission spectrum are visible?

Why are only certain colors of the emission spectrum in Hydrogen visible?
28. ### Hydrogen Epoch of Reionization Array

Does anyone have any experience with the Hydrogen Epoch of Reionization Array project? I'm working on it over the summer, and I'd like to know what its like form someone who has done it.
29. ### Boltzmann Partition Function of H_2

Homework Statement In the real world, most oscillators are not perfectly harmonic. For a quantum oscillator, this means that the spacing between energy levels is not exactly uniform. The vibration levels of an ##H_2## molecule, for example, are more accurately described by the approximate...
30. ### A Lyman-alpha forest: why not Lyman-beta?

Hello everyone! We observe the so-called Lyman-alpha forest in the spectrum of distant quasars and it is said that these multiple absorption lines are due to the presence of intergalactic HI clouds that absorb light at the wavelenght of 1216 A , the Lyman-alpha transition. My question is the...
31. ### Why is hydrogen added to BWR coolant but not PWR coolant?

I know hydrogen gas is used in BWR coolant to counteract radiolysis and reduce the probability of localized corrosion. Why can't the same be done for PWR's?
32. ### Kinetic energy of the hydrogen atom in its ground state

I saw another post about this but i didn't quite find what i was looking for there so i thought i'd give it a go instead with a thread. Homework Statement Calculate the exact value of the kinetic energy of the hydrogen atom in its ground state. No more information is given, we are referred to...
33. ### I Hydrogen Wavefunction Doubts

Hi, I am a physics student and i was asked to answer some questions about Hydrogen atom wavefunctions. I hope you can help me (sorry for my english, is not my motherlanguage, i will try to explain myself properly) 1. In order to find hamiltonian eigenfunctions of Hydrogen atom, we make then be...
34. ### Temporary high-pressure Hydrogen storage?

I've been looking into compressed Hydrogen storage, and it seems that the high pressure containers have a lot of layers on the inside to keep the Hydrogen from leaking out/diffusing over the lifetime. However now I'm curious as to whether you could use a tank to store high-pressure Hydrogen (in...
35. ### Using electrochemical hydrogen compressor in reverse

Electrochemical hydrogen compressors (https://en.wikipedia.org/wiki/Electrochemical_hydrogen_compressor) basically convert an electrical potential difference into a pressure difference. Would it be possible to run one of these in reverse, i.e. using a pressure difference to create a voltage? If...
36. ### Speed of Hydrogen combustion out of a tube?

Hello, I was curious about how to calculate how fast the escape velocity of hydrogen out of a tube/cylinder would be. Once end of the cylinder is closed, the other is open, obviously. Assume the cylinder is full of hydrogen at 1 atm. My thought is that you could use PV=NRT to calculate the...
37. ### Atomic Conservation in Ionized Hydrogen Gas

Dear all, So I have a question concerning atomic conservation in an ionized hydrogen gas. So imagine we have ## H_2 ## initially. Later the gas is taken to an appreciable temperature such that at equilibrium the following species are present, ## e^-, \ H, \ H^+, \ H_2, \ H^-, \ \text{and} \...
38. ### Hydrogen fuel generation

I would like to start experimenting with hydrogen as an electricity source, but I haven't been able to find any good resources for steps after the hydrogen generation. I've made some prototypes of small-scale hydrogen generation using electrolysis, so now I basically have two bags, one filled...
39. C

### Electric Potential and Ionization Energy of Bohr Hydrogen

I was studying for (first year) physics class and was playing around with the Bohr Model of Hydrogen. I tried calculating the electric potential at the Bohr radius r =5.29e-11 m, where V = \frac{e}{4 \pi \epsilon_0 r} (from the point-charge formula for electric potential) and I got 27.19 J/C...
40. ### Nylon deterioration from hydrogen released water vapor?

Hello, I am by far not very firmiliar with physics nor engineering. I had an idea a couple years ago involving the replacement of the propane in hot air balloons with hydrogen gas as the fuel to burned to provide the heat to lift the balloon. One thing I didn't realize back then was that...
41. ### Plotting the Probability Density of the Coulomb Wave Function

Hey there - I think I have an issue with my 3D density plots of the probability density of the Coulomb wave function. The reason I think something is going wrong is because my plots of |ψ(n=2, l=1, m=-1)|² and |ψ(2, 1, 1)|² are identical, while I would expect them to have the same shape but be...
42. ### Dimensionless Radial Equation Hydrogen Atom

Homework Statement Show that in terms of the dimensionless variable ##\xi## the radial equation becomes ##\frac{\mathrm{d}^{2} u}{\mathrm{d} \xi^{2}}=(\frac{l(l+1)}{\xi^{2}}-\frac{2}{\xi}-K)u## Homework Equations ##u(r)\equiv rR(r)## ##\xi \equiv \sqrt{2\mu U_{0}}\frac{r}{\hbar}##...
43. ### H2O, HDO, D2O equilibrium concentrations

I have seen something to this effect stated dozens of times on the internet : "..because the deuterons and the protons are exchanging so quickly, you will end up with a statistical distribution: 25% H2O, 25% D2O, and 50% HDO." They are referring to a sample of water which is 50 atom %...
44. ### Hydrogen/Helium Emission Spectra Temperature Dependence

Hi all, Does anyone know where I can find data details of how Emission Spectra depends on temperature for the following materials: Single Hydrogen Molecular Hydrogen (H2) Helium That is, as I heat up each of the above materials by themselves, from room temperature to thousands of degrees, I'd...
45. ### Liquid Hydrogen Boil-off

I've read a fews post about liquid hydrogen boil off, but could use a bit more clarification; insight on the following thought experiment would be really helpful: What happens if I take a 1 L steel vessel, put 1 L of liquid H2 into it, seal it off, and let it sit in a room at 25C? The density...
46. ### Question about spectral emission measurements of hydrogen

Looking for typical experimental parameters for measuring emission spectrum of both H and H2, specifically gas pressures. Also would like to know typical pressure range where spectrum transitions from H2 to H. Thanks.
47. ### Radiation of accelerated charge in QM

Hi, One of the main problems of the Rutherford model is the fact that the electrons are accelerated and hence should lose energy due to radiation. Bohr's model doesn't resolve this, it only postulates that the energy levels are quantized and energy can only be emitted or absorbed by jumping...
48. ### Hydrogen energy levels question

Homework Statement Draw an energy level diagram for hydrogen (use the vertical direction for energy and separate the states horizontally by angular momentum l) Homework Equations I've got some fundamental misunderstandings with this one. I thought the energy levels of hydrogen were given by...
49. ### Hydrogen oxygen ignited volume expansion

Homework Statement there is an expandable container with 1m3 of hydrogen and 1/2 m3of oxygen at stp. the gas is ignited.what is th final volume if there is no heàt lost and the pressure outside the container is 1atm? assume complete combustion Homework Equations other than the ideal gas...
50. ### Measuring redshift from type 1a supernova

I know that you can measure redshift from stars by looking at the shift in there balmer lines or more generally there line absorption spectra and seeing how far these lines have shifted from actual balmer lines or line absorption spectra of the same elements on earth. But how would you...