Questions tagged [elements]

Questions with this tag should involve the elements on the periodic table and their different properties.

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Cobalt atomic mass less than 100 % isotope mass? [closed]

Why is cobalt's atomic mass listed on periodic tables as less than 59 amu when its main isotope (virtually 100 %) is cobalt 59 with a trace of cobalt 60? After reading a bit I'm wondering if it has to ...
AZ273026's user avatar
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11 votes
2 answers
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Is there proof for: "Elements heavier than iron will decay to iron by processes such as fission and alpha emission"?

Freeman J. Dyson in his "Time without end: Physics and biology in an open universe", Lecture 2: Physics, part G: All matter decays to iron, claimed that on a long enough time scale "...
Sourabh Choudhary's user avatar
22 votes
1 answer
5k views

Why is helium-4 the only nuclide with a negative nucleon binding energy?

He-4 is very unusual as it’s the only nuclide that does not accept another nucleon. In other words, even if you force a proton or a neutron into He-4, it will be kicked out immediately. If you ...
哲煜黄's user avatar
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Most stable isobar in case of even-$A$ nuclei

In the Liquid Drop Model of the nucleus, the most stable isobar is the one whose atomic number $Z_{A}$ is the one corresponding to the minimum mass, and can be found from the mass parabola or, by ...
Momo's user avatar
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0 votes
2 answers
129 views

Why are lithium and beryllium such good conductors but not chlorine?

Why are lithium and beryllium so conductive? The $2s$ band has a much different energy range from the $2p$ band, so I guess the only explanation is that $N$ states are empty. But if that was the case, ...
Root Groves's user avatar
1 vote
0 answers
46 views

Why can't massive nuclei combine together to release energy

I am basically confused as why can't larger nuclei undergo fushion and release energy. One reason I know is because of too much protons than neutrons which generates stronger electrostatic repulsive ...
EBoiG _XF65's user avatar
1 vote
1 answer
149 views

Have nuclear physicists ever turned lead into gold?

The holy grail of ancient alchemy was a process for converting lead into gold. (Well, for some alchemists, the true holy grail was, in fact, the actual Holy Grail. But that's another topic entirely.) ...
tparker's user avatar
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3 votes
1 answer
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Why is the nuclear binding energy per nucleon not constant at beginning?

I can understand, how it is constant after awhile, that due to the range of strong nuclear force the force is increasing linearly with the linear increase of the nucleon number, making it a constant. ...
Razz's user avatar
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1 vote
0 answers
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Finding exhaustive list of isotopes known to have the induced-fission property [closed]

Not sure if this is the right place to ask, since I am looking for help finding information. I am making course material in low level nuclear physics. For this, I've created my own visual Segre Chart (...
nammerkage's user avatar
2 votes
0 answers
116 views

Understanding the Nuclear Spin of Boron-10: Why is it Spin-3?

I am delving into the nuclear spin characteristics of Boron-10, which notably has a nuclear spin of 3. While I have a foundational understanding of some quantum mechanical principles, the specific ...
Darkorse's user avatar
1 vote
0 answers
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Nuclear physics explained by QCD

I have been studying Particle & nuclear physics and I know that nuclear physics should normally be explained by particle physics. Specifically, I would like to ask if there is any theoretical ...
Georgia Zachou's user avatar
8 votes
2 answers
677 views

What might be the half-life of observationally stable nuclei with energetically favorable decay modes?

For example, a reaction $${}^{132} \mathrm{Ba} \rightarrow {}^{128}\mathrm{Xe} + \alpha + 22.19\mathrm{keV}$$ would be energetically favorable, contrary that ${}^{132} \mathrm{Ba}$ is observationally ...
peterh's user avatar
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1 vote
1 answer
118 views

Is there a way to determine whether a given nucleus is radioactive?

When a nucleus decays it is finding a more stable configuration, as all nature is. But is there a way of finding whether a specific configuration will decay? I know that there is a specific proton-to-...
Saksham's user avatar
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-3 votes
1 answer
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Can moscovium-299 exist and is it possible to predict how stable it will be?

Five isotopes of element 115 (moscovium) have been created in the laboratory with atomic weights ranging from 286 to 290, each having a progressively longer half-life, ranging from 20ms to 650ms: ...
Larry's user avatar
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0 votes
1 answer
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Where are the Gamma rays in Beryllium-7 decay coming from? [closed]

Beryllium-7 decays via electron capture. This gives of Neutrino and later a Auger electron/Extreme ultraviolet photon. So where does the Gamma rays that occur 10% of time according to here come from?
blademan9999's user avatar
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3 answers
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What is the difficulty of determing the products of nuclear fission?

In my impression, initially many people did not believe that an Uranium nucleus disintegrates into two halves when bombared with neutrons. Experimentally, there must be some difficulty to determine ...
poisson's user avatar
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Are very stable super-heavy elements theoretically possible?

I was recently reading about superheavy elements. According to that article all superheavy elements currently known have only been synthesized in laboratory experiments and have a very short half-life,...
LorenzoDonati4Ukraine-OnStrike's user avatar
0 votes
0 answers
36 views

How does the increased binding energy per nucleon help in stability?

I have some read answers on this forum, some books like Halliday Resnick and my course books. I have understood that binding energy is the energy we need to supply to break nucleus into individual ...
Ayush's user avatar
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3 votes
1 answer
562 views

Does every element have a critical mass?

We have all heard of critical mass for radioactive materials like Uranium, Plutonium etc. but does every element theoretically have a critical mass? If not, what determines if such a phenomena is ...
Derek Seabrooke's user avatar
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0 answers
62 views

Radioactive Decay of Li-8

Currently using a simulation to observe the decay of various elements. I noticed for the Li-8 there is beta decay. There are also arrows pointing from beta decay towards alpha decay and stable. Can ...
Jordi Ali's user avatar
1 vote
1 answer
100 views

Binding energy per nucleon vs binding energy

What is the physical difference between binding energy and binding energy per nucleon? Which one is the energy required to split nucleus into individual nucleons?
Neha L's user avatar
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1 vote
0 answers
537 views

Periodic Table of Elements Resonant Frequencies (Resonant, Emitted and Absorbtion)

I'm looking for a nice PTE chart that gives the frequencies of each element by Fraunhofer scale. Any help?
1 vote
0 answers
35 views

If there wasn't a weak nuclear force, what would be the heaviest stable theoretically stable isotope with equal protons and neutrons?

If there was no weak nuclear force, what would be the heaviest stable theoretically stable isotope with equal protons and Neutrons? For our universe the heaviest such isotope is calcium 40, but most ...
blademan9999's user avatar
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2 votes
3 answers
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Mass per nucleon graph

I am a high school student and am struggling with understanding the significance of the mass per nucleon graph. What does this graph show with regard to nuclear reactions? (y-axis: M/A, x-axis:A) I ...
Authentic Melody's user avatar
4 votes
2 answers
310 views

Why is polonium so unstable compared to bismuth?

Why is polonium so much more radioactive than bismuth? I've been wondering this for a while, and have searched around for an answer, but I can't seem to find anything that gives a good answer. Bismuth-...
electricpants's user avatar
6 votes
1 answer
299 views

Why is lithium burned at lower temperatures than hydrogen inside stars?

The destruction of lithium inside stars through the reaction $$ ^{7}_{3}{\rm Li} + {\rm p} \rightarrow 2\ ^{4}_{2}{\rm He}$$ takes place at just $\sim 3\times 10^6$ K. This is much lower than the ...
ProfRob's user avatar
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4 votes
0 answers
73 views

Could there be undiscovered long-lived isomers of unstable elements? [duplicate]

There are 80 stable elements in the periodic table. These elements have at least one stable isotope. Other elements don’t have any identified stable isotopes. The existence of stable isotopes can be ...
哲煜黄's user avatar
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13 votes
4 answers
4k views

How it was found that 12 g of carbon-12 has Avogadro's number of atoms? [duplicate]

I just want to know the history of finding Avogadro's number of atoms in 12 gm of C-12 and why C-12 only? Like I was asking how scientists came to conclusion that there is exactly 6.023*10^23 atoms in ...
S.Rishabh's user avatar
  • 147
2 votes
2 answers
208 views

Why isn't lead-207 radioactive?

I've recently learnt from here, in an atom, the stability of an atom is described in two contexts, one according to the ratio of neutron and proton of the atom. The ratio will always be between 1 and ...
Projesh Datta's user avatar
1 vote
1 answer
107 views

Why are magnesium and calcium crystals, metals instead of insulators/semiconductors?

Consider the outer-most s orbitals for Mg or Ca solid. They will form one band. The 2 electrons in the outer-most shell fill this band. Shouldn't the next p orbital band be above the fermi level and ...
Bohan Xu's user avatar
  • 633
1 vote
0 answers
20 views

Is an object's pressure on a surface, affected by the type of surface?

Is an object's pressure on a surface, affected by the type of surface. For example, if a chunk of metal gave a pressure of $2800 \ pa$ on a table, would it still give a pressure of $2800$ on dust/sand,...
Xiao's user avatar
  • 19
0 votes
2 answers
292 views

Why we consider varying height of element in calculating COM of solid hemisphere but not for hollow hemisphere?

This is how we calculate COM(centre of mass) of hollow hemisphere. We take dA=2piR²cos(theta)d(theta). But while calculating COM for solid hemisphere using this method if taken dV= piR³cos²(theta)d(...
Arpit Raj Choudhary's user avatar
0 votes
1 answer
46 views

Why $\rm Ag$ 108 decays into $\rm Cd$ 108 most of the time?

In the table of nuclides, it shows that $\rm Ag$ 108 can go through either electron capture or beta- decay (though the branching ratio for electron capture decay is much lower). What determines that? ...
Anonymous's user avatar
0 votes
1 answer
101 views

Why can a non-Metalloid be a Semiconductor?

I was reading that the first description of a semiconductor material was made by Michael Faraday in 1833 and published in Experimental Researches in Electricity.-Fourth Series (https://www....
Nau's user avatar
  • 447
3 votes
2 answers
1k views

Why do elements, as they have more protons, need a higher amount of neutrons to stabilise them? [duplicate]

I've seen the graphs of the stability line but I can't find any reason as to why this happens, I understand radiation, just not why radiation needs to occur in the first place if that makes sense.
Amy Cooper's user avatar
0 votes
0 answers
37 views

How can a proton in a nucleus decay into neutron and positron in β+ decay if neutrons have greater mass than a proton? [duplicate]

I'm guessing it has something to do with mass defect/binding energy??
Mahmodol's user avatar
-1 votes
1 answer
188 views

Why is it when an atom gains a proton it is said to become an 'atom' of a different element?

My confusion lies in that the number of protons in the nucleus will increase but is the number of electrons assumed to automatically follow suit such that the result is a neutral atom with equal ...
open's user avatar
  • 13
0 votes
1 answer
24 views

What is the name of the instrument that separates substances using an electromagnetic field, similar to spectrography

As far as I remember, the elements of the substance are passed across an electromagnetic field in such a way that they seperate as the electromagnetic field alters their trajectory. I also seem to ...
Archie Lister's user avatar
6 votes
1 answer
672 views

Large difference between the atomic sizes of uranium and thorium

According to Villars and Daams [Journal of Alloys and Compounds, 197 (1993) 177] the atomic volume of U is $2.073\times10^{-2}\,\mathrm{nm^3}$, whereas that of Th is much larger, $3.295\times 10^{-2}\,...
gryphys's user avatar
  • 496
0 votes
2 answers
198 views

How were the electrons, protons counted in an atom?

The title says it all! In high school I remember it being taught as a religion, I had to believe the count (hydrogen has 1 proton, carbon has 6 etc...) , but how can I be sure I was told the truth?
Aminos's user avatar
  • 141
2 votes
1 answer
36 views

Is there an online resource for fusion outcomes of various elements at various energy levels?

I'm looking to find a chart of nuclides, their potential fusion products and measured energy levels, in a similar vein as NuDat 3, but for fusion. It doesn't need to be cleanly formatted like NuDat, ...
0 votes
1 answer
75 views

Why can't one calculate the energy of the one electron Uranium ion state with the Dirac equation?

In the link, Solving Dirac for one electron atom/ion the energy for the one electron $s_1$ shell is calculated as $$ E=m_{\mu}c^2\left( 1 - \frac{1}{\sqrt{1+\left( \frac{\alpha Z}{n-j-1/2 + \sqrt{(j+1/...
Stefan's user avatar
  • 371
1 vote
1 answer
338 views

What is the Hydrogen and Helium composition of the Sun in terms of their different states?

What is the Hydrogen and Helium composition of the Sun in terms of: Hydrogen: (1) molecular, (2) metallic and (3) ionized compositions? and Helium: (1) atomic, (2) metallic and (3) ionized ...
Brendan Darrer's user avatar
0 votes
1 answer
182 views

Specific heat of ionised Helium in the Sun?

What is the specific heat of ionised Helium, given as ergs/g/K? This seems to be very difficult find on the internet. This is in the context calculating the total heat of the Sun which is given as ...
Brendan Darrer's user avatar
-5 votes
1 answer
149 views

How to make a new element from an existing one? [closed]

So my question is, how can I create a new synthetic element from some existing element. I want to create eka-francium. Now, what would be the best way for me to may it? Should I use a particle ...
Tsar Asterov XVII's user avatar
1 vote
0 answers
56 views

Why we do not get naturally occurring elements with atomic number greater than 92? [duplicate]

Why we do not get naturally occurring elements with atomic number greater than 92? I know that some arguments suggests that the reason is that all the elements with atomic number from 93 are highly ...
Neutralino's user avatar
3 votes
3 answers
1k views

Does every element have a half-life?

Will every element slowly decay into something else? Or do some isotopes have infinite half-lives?
SwagnLag's user avatar
2 votes
1 answer
375 views

Why is Zirconium neutron transparent while Hafnium is such a neutron absorber?

Out of curiosity I've been researching about Hafnium and Zirconium. I'm curious as to why Hafnium (below Zirconium on the periodic table) is so often used in control rods, while Zirconium is ...
Jlalonde's user avatar
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0 votes
0 answers
53 views

Heat of Sublimation of GaAs and SiC

I am trying to find values for the heat of sublimation of GaAs and SiC, but can't find anything. I also tried searching for the heat of fusion and vaporization, to calculate the heat of sublimation ...
jochdi's user avatar
  • 1
3 votes
1 answer
390 views

Is atom vibration (not speed) correlated with temperature?

As far as I know every atom vibrates / oscillates / I don't know what it's called in English with a frequency, specific for its element. I don't mean the velocity of the atom, which defines ...
mummy's user avatar
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