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Every known element has a unique atom?

  1. Dec 19, 2014 #1
    This notion perplexes me. Could I please have this explain with an example(s). I am confused are atoms not made up of the same protons and neutrons which are just essentially negatively or positively charged particles which are made of quarks? Which as confusing as that can become. How can one atom be unique from the others when they are made of the same negatively and positively charged particles?

    Thank you
  2. jcsd
  3. Dec 19, 2014 #2


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    The key here is to understand that each particle is indistinguishable from any other particle of an identical type. In other words, all protons are indistinguishable from all other protons, and all down quarks are indistinguishable from all other down quarks. This just means that if we do an experiment, say to measure some value such as mass or charge, we get the same measured values no matter which particle we measure. All protons have identical mass, charge, etc, and all down quarks have identical mass, charge, etc.

    Now, just because two particles may be indistinguishable does not mean that they aren't distinct, separate objects. A proton in my hand is not the same proton that's in my cup.
  4. Dec 19, 2014 #3
    I understand that particles are indistinguishable but how can they be of different types? If as you said all protons are indistinguishable from other protons and same with quarks. Therefore, they are all the same things. How can anything be any different from each other? Where is the distinction made or how can there be? How does an atom become distinct maybe is a better why of phrasing this, if indeed they are all the same underneath it all.
  5. Dec 19, 2014 #4


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    The atom as a whole object becomes distinct from other atoms based on the number of particles making it up. With different numbers of protons and neutrons, the atoms no longer behave identically. The number of protons directly determines the number of electrons the atom can attract, which then determines the different chemical properties we see from each element.
  6. Dec 19, 2014 #5


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    I wonder if what he is asking is: how are nitrogen and oxygen so different if they are both made of protons, neutrons and electrons.

    The answer is that the number of protons has a direct effect on the number of electrons. It is the number electrons (and placement) that is the basis for all chemistry.
  7. Dec 19, 2014 #6


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    Is one familiar with the periodic table? The periodic table arranges elements according to similar chemical properties, which are based on the number of electrons in the atoms of a particular element. The nature of an element is determined by the number of protons in the nucleus. Elements have isotopes, which means nuclei with the same number protons, but different numbers of neutrons in the nucleus. While the chemical properties of isotopes are similar or more or less the same, the nuclear properties are different.

    In general, atoms tend to be neutral, with the number of electrons equaling the number of protons in the nucleus. Electrons occupy particular energy levels, and the outermost (valence) electrons determine the chemical properties.

    Some nuclei are stable, i.e., over time, the nucleus remains unchanged. Some nuclei have a deficiency or excess of neutrons in relation to the protons, and such nuclei can be radioactive, i.e., the nucleus with change through beta decay or positron emission, or electron capture, or in some cases, for the heaviest nuclei, by alpha decay.
  8. Dec 19, 2014 #7


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    I think you are getting confused because you don't understand atomic structure.

    An atom is made up of a nucleus, which can contain one or more protons (positively charged), and zero or more neutrons (no charge). Outside the nucleus, there is a group of much lighter particles called electrons (negatively charged).

    Early models of the atom had the electrons orbiting the nucleus, much as planets orbit the sun, but later research has shown that those early models don't accurately reflect the true structure of the atom. The orbital paradigm persists because it simplifies the teaching of elementary chemistry.

    Each element contains a unique number of protons in its nucleus. Hydrogen is the simplest element, because its nucleus contains just one proton. Helium is next, with two protons, all the way up to uranium with 92 protons. The number of protons in the nucleus of an atom is also called the atomic number.

    The nucleus of an atom may also contain a certain number of neutrons. If two atoms of an element contain different numbers of neutrons in the nucleus, then you have different isotopes of the same element. For example, hydrogen has three isotopes: H1 contains a single proton in the nucleus, H2 contains a proton and a neutron, and H3 contains a proton and two neutrons. These are all forms of hydrogen because each nucleus has only one proton.

    The chemical properties of an element are determined by the arrangement of the electrons surrounding the nucleus. The electrons arrange themselves in a certain order, depending on their total number. Each atom of an element contains the same number of electrons as it has protons in the nucleus. The number of electrons in the outermost positions determine if an element is very reactive (like sodium or potassium) or relatively inert (like lead).

    All atoms of hydrogen will react chemically in the same way. All atoms of lead will react chemically in the same way. Lead and hydrogen will react differently chemically, because the arrangement of electrons is different in lead from the arrangement of electrons in hydrogen.

    Things like quarks play no role in the chemistry of an atom, beyond making up the protons and any neutrons in the nucleus. Quarks are thought to be the constituent parts of protons, neutrons, and other subatomic particles.
    Last edited: Dec 20, 2014
  9. Dec 20, 2014 #8


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    What Steamking said. It's the number and arrangement of these particles that affects their chemical properties..

  10. Dec 20, 2014 #9
    Nice presentation. Just realize the atomic orbitals don't exist quantumly until they are located classically, in respect to the "orbital shell". Quantum probability "expands" per "orbital" level?
  11. Dec 20, 2014 #10


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    Uh, huh. You've been playing with your protons again, I see.
  12. Dec 21, 2014 #11


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    My bike and my car are made from exactly the same elements (and effectively from exactly the same elementary particles) yet they are completely different. Why would you expect them to be identical?
  13. Dec 21, 2014 #12


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    You should not get involved with Quarks until you are much firmer on Classical Atomic Theory. All that was sorted out very satisfactorily, long before the structure of Neutrons and Protons was understood to the level it is today.
    A thought for Christmas, with which you can impress your friends: Did you know that the word 'Isotope' comes from the Greek words for Same and Place. (i.e. the same place in the periodic table)? It's the place in the periodic table that governs how an atom will behave chemically. Effects of the small differences in atomic masses are very much more subtle that what other atoms they will combine with.
  14. Dec 22, 2014 #13
    Just saying but any process at a subatomic level such as electron orbitals is by definition a quantum process for example they undergo quantum leaps when they change energy levels, electrons also follow a partical/wave duality. I hope this sheds some light on a physical chemistry perspective for you
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