# Tag Info

29

You are using the Heisenberg uncertainty principle to relate the uncertainty in position $x$ to the uncertainty in velocity $v$. However, the quantitative version of this principle actually is $$\Delta x\cdot\Delta p\geqslant\tfrac12\hbar$$ where $\Delta x$ is the uncertainty in position $x$ and $\Delta p$ is the uncertainty in momentum $p$. Certainly, ...

23

Yes and no. Elements are defined by the number of protons only. It does not matter if (say) a carbon nucleus has six or seven (or eight) neutrons, they will all react the same.* With that, to create new elements, you would need to get up to some 115 or so protons fused together. But there is a reason for neutrons: all the positively charged protons in the ...

20

Jan's answer is correct. I will try to fill in a few details about why neutrons are essential to creating stable nuclei. All stable isotopes excepting Hydrogen-1 have neutrons in their nuclei. Hydrogen, for example has two stable isotopes: The first simply has a proton with no neutrons in the nucleus, while the second, often called Deuterium has a proton ...

15

But in the case of protons, we are kind of certain about their position in the atom. Well, yeah, kind of certain. The very notion of molecular geometry arises in the Born-Oppenheimer approximation. Nuclei are much heavier than electrons so that when solving the electronic Schrödinger equation they can be assumed to be stationary. This clearly violates the ...

13

Is it possible to remove a proton from the atom via some technique such as bombardment with another particle or applying an appropriate amount of energy to the system? Yes, this occurs in nature and can also be done in the laboratory. In nature the process is known as radioactive decay. Listed below are two decay processes that will remove a proton(s) ...

11

There are actually a (very small) number of nuclei that exhibit spontaneous proton emission decays. Much more common are photon, neutron or alpha initiated proton emission reaction such as the the alpha initiated reaction on Sulfur discussed in this pre-print. Moderate energy alphas incident on light nuclei generate many interesting final states a fact that ...

10

$\ce{H3O^+}$ is really just a "shorthand notation" for what really occurs in solution. Typically higher hydrates of the proton, particularly $\ce{H5O2+}$ the "Zundel" cation and $\ce{H9O4+}$ the "Eigen" cation are thought to be the main players in the proton transfer process. As permeakra has pointed out, Grotthuss was one of the early pioneers studying ...

9

The gold foil experiment conducted by Rutherford (or more appropriately by Geiger and Marsden under Rutherford's direction) involves a stream of $\alpha$ particles (which are helium nuclei) bombarding a thin gold foil. Why didn't some electrons go with the alpha particles because of electrostatic attraction? Some probably did. The experiment was equipped ...

9

I'll focus on the nucleus only. As far as I'm aware, there is little to no variation in radioactive decay lifetimes as a function of ion charge state; that is to say that the number of electrons surrounding a nucleus has little to no impact on whether the nucleus will decay. I'm open to corrections from measurements at, say, the Hollifield facility at Oak ...

8

That's more a nuclear physics question. But I will write some anyway. First, there is a good amount of naturally radioactive nuclei, that emits alpha particle, i.e. $\ce{^4He}$ nucleus. Than, there is a less common $\beta^+$ decay, when nucleus emits positron, transforming one proton into neutron in the process (and emitting neutrino). Next, some nuclei ...

8

A free neutron is not considered to be an element and there is no element that does not have at least one proton. Free neutrons could be included on the graph as they are unstable and decay with a half life of around 10 minutes ($611.0\pm1.0~\mathrm{s}$) although most versions I have seen do not usually include them as they aren't really nuclei which is ...

7

In the most common case you can only observe 3J-couplings, any spins further away than three bonds do not cause a visible splitting in your spectra. The exception are couplings via double-bonds or aromatic systems, there you can often see small couplings over four bonds. In this case the spins are too far away from each other to cause a visible splitting, ...

7

Most of chemistry doesn't care a whit about all of the properties you named: they're in the realm of nuclear physics, as noted by user badjohn. Even radioactive decay is something of a black sheep, included in physical chemistry as a convenient example of a first-order kinetic process. To my knowledge, it's not substantially used in conjunction with any ...

6

A quite complete procedure in the calculation of proton affinities from ab initio calculations is referenced in an article by H. Audier et al., Int. J. Mass Spectrom. 1996. It goes much further in the procedure than only on the calculation of the enthalpy of a proton (including corrections due to the basis set superposition error and so on), but confirms ...

6

I don't have much knowledge of Nuclear Chemistry but: is it possible that by any method like bombarding other particle or providing high energy can we remove proton from atom ? The best example that I can think of right now is alpha decay. An alpha particle consists of two protons and two neutrons bound together into aparticle identical to a helium ...

6

For charge neutrality, the number of electrons has to equal the number of protons. So, the question really is how to know how many protons and how many electrons. This is actually a very interesting question dating back to the early days (and even before) of nuclear physics and chemistry. Now, one can do it fairly easily with an ion accelerator and a ...

6

Your example with deuterons is unfortunate as they are composed of protons and neutrons and, as such, formally putting deuterons together would just reconstruct the periodic table we know. However, there are atoms with particles other than protons, neutrons and electrons. Two relevant terms to refer to such are exotic atoms and hypernuclei. One of their main ...

6

Your teacher said that this is not completely correct as there are (at least) three common definitions for acids and bases (Wiki has a good article for this https://en.wikipedia.org/wiki/Acids_and_Bases): Arrhenius: In water, acids under this definition protonate the water and form Hydronium (H3O+). Bases in this definition deprotonate the water. Brønsted–...

6

This occurs during Oxidative phosphorylation and the "proton leak" process is also called Uncoupling of Oxidative Phosphorylation The mitochondrial electron-transport chain Electron transport, causes Complexes I, III, and IV to transport protons across the inner mitochondrial membrane from the matrix, a region of low [$\ce{H+}$] and negative electrical ...

5

Without getting into the specifics of nuclear forces, there is a simple way to think about this. What matter for chemistry is the number of protons in the nucleus of the atom as this determines the nature of the electron orbitals the atom will have which is what chemistry is about. So, if you could persuade electrons to joint the nucleus and that led to a ...

5

Absolute mass can be determined electrochemically, once the coulomb is defined in terms of numbers of electrons, as through the Millikan oil-drop experiment, to be $6.24×10^{18}$ electrons per coulomb. See Determination of Avogadro's Number and Absolute Determination of the Electrochemical Equivalent and the Atomic Weight of Zinc. One thing that ...

5

We do not know. Physicists THINK that there ought to be a fundamental limit in scale for space-time that occurs near $10^{-33}$ centimeters and $10^{-43}$ seconds; often called the Planck Scale. There is also a unit of mass associated with this scale which is about $10^{-5}$ GRAMS or $10^{19}$ Billion Electron Volts (BeV or GeV). It is a simple matter to ...

5

In theory, this structure is expected to provide four different signals: a broad singlet, due to the potential exchange of the phenolic OH a singlet accounting for three protons of the methyl group and signals for the remaining four aryl protons ... which may be tricky The chemical shift of the aryl protons is influenced by the two, para standing towards ...

5

Protons in nucleus no doubt are repelled by each other. But we know that an atom is stable. The reason for this is that the protons and the neutrons(together called nucleons) are attracted to each other by a strong for called nuclear force. This force acts only in the distances of orders of angstrom or picometre. As mentioned earlier, not only protons are ...

4

Yes, it is actually the main reason for superior mobility of hydrogen ion in water solutions see the link: http://en.wikipedia.org/wiki/Grotthuss_mechanism

4

Protons attached to a carbon that is connected to a benzene ring typically resonate in the range 2.2-2.9 ppm (see the Ar-CH range in this table). Here is the proton nmr spectrum for ethylbenzene. The methylene protons absorb around 2.7 ppm, right in the upper end of the expected range. image source

4

To answer this question, I am going to assume that a $\ce{^2He}$ nucleus actually exists long enough for two electrons to surround it — this is probably not a valid assumption since Webelements.com does not list $\ce{^2He}$ while it does list the isotopes $\ce{^6He}$ and $\ce{^8He}$ (although they admittedly have long half-lifes measured in tenths of seconds)...

4

We may regard the calcium hydroxide and calcium carbide as essentially ionic except for the covalent bonding within the anions. So there is no Lewis reaction involving the calcium. That leaves the proton transfer, which can be described fully by the B-L theory. You actually have two reactions, successively forming $\ce{C2H-}$ and then $\ce{C2H2}$.

4

Moseley measured the atomic number in 1913 with relatively modest equipment (by modern standards) but I doubt that you could reproduce his experiments in a typical kitchen. Atomic number at Wikipedia Expansion as suggested in comments. Here is a quote from that article of what he did. "Moseley measured the wavelengths of the innermost photon ...

4

You have it a little backwards. We don't observe charge, and then infer the existence of a force. It's the other way around. We observe forces between objects -- they repel or attract each other -- and then build models which explain which objects are attracted or repelled by which other objects, and by how much. That leads us to invent the idea of ...

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