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Consider a neutral atom that has $n$ protons and $n$ electrons. 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?

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up vote 7 down vote accepted

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)

  • alpha decay: an atom ejects a helium nucleus (2 protons and 2 neutrons) $$\ce{^239_94Pu -> ^4_2^He + ^235_92U}$$
  • beta-plus decay: a positron is emitted and a proton is converted to a neutron.

In the (nuclear) lab, a process known as phototransmutation can be employed. If a nucleus is irradiated with high-energy gamma rays (high-energy photons) it can absorb the energy and change to another element by ejecting a proton and\or neutron $$\ce{^25_12Mg ->C[{h\nu}]\ ^1_1^H + ^24_11Na}$$

You can make a rough estimate of the energy required as follows: $$\ce{24$.$98583692~ amu~ ->~ 1$.$00727647 amu + 23$.$99096278~amu}$$ comparing the starting and final mass, we find that 0.01240233 amu has been gained in the process. Since 1 amu = 931.5 MeV, the gamma ray photon would have to have an energy of at least 11.6 MeV.

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In the most extreme case, some of the earliest stars in the universe may have been destroyed when temperatures in their cores produced photons with enough energy to shatter atomic nuclei completely and drain the energy that was preventing gravitational collapse: – Dan Neely Jul 18 '14 at 20:00
@ron Is this concept explain by you is applicable for elements having atomic number more than 60 . – Murtuza Vadharia Jul 20 '14 at 4:34
@ron Suppose For example can I remove 1 proton from mercury by alpha decay method or beta plus method? – Murtuza Vadharia Jul 20 '14 at 4:38
@murtuza vadharia There are no naturally occurring radioisotopes of mercury. However, there are short-lived (seconds to hours) isotopes of mercury that are formed by radiodecay of a parent nuclei and that undergo alpha and \or beta-plus decay. For details see, P.S. If the answer above was helpful, please mark it as accepted, thanks. – ron Jul 20 '14 at 12:03

There are actual 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 Sulfer discussed in this preprint. Moderate energy alphas incident on light nuclei generate many interesting final states a fact that has been instrumental in figuring out how the nucleus works (which is admittedly usually framed as a physics rather than chemistry question).

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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 nucleus.

This is also what we do in nuclear fission/fusion [atom bomb etc.]. But I think adding or removing just one proton might be very hard.

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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 captures electron (usually from lowest electron shell), emitting neutrino and again, transforming one proton into neutron. Proton emission is known, but extremely rare.

Next, there is some amount of nuclear reactions, when an incoming hi-energy particle merges with nucleus, than the resulting excited nucleus emits some other particles. This reactions are extremely specific, each pair of nucleus and particle has their own reactions routes, etc, etc. Example of proton-emitting reaction:

$\ce{\ ^3He + D = ^4He +^p}$

Sometimes, heavy nuclei after capturing a neutron, undergoes $\beta$-decay, transforming into $\alpha$-radioactive nuclei. The net result would be losing a proton and maybe a neutron or two. But this an awfully specific for few nuclei.

TL;DR : no, there is no general technique, but there are some techniques (very costly), than work in some specific cases.

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