![]() ![]() Their properties and interactions are described by nuclear physics. Since protons and neutrons behave similarly within the nucleus, and each has a mass of approximately one dalton, they are both referred to as nucleons. Protons and neutrons constitute the nuclei of atoms. , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. The neutron is a subatomic particle, symbol < 1.8 ×10 −26 e⋅cm (experimental upper limit) Forces between quarks are mediated by gluons. The color assignment of individual quarks is arbitrary, but all three colors must be present. Something must be PRODUCING the stuff even as we sit here staring at a computer monitor.The quark content of the neutron. Now, knowing that the half-life is only about 6,000 years, and the age of the Earth is about 4 billion (4*10 9) years, it doesn't take an Einstein to see that ALL of the carbon-14 should have converted to nitrogen long ago. ![]() Carbon-14 is a popular atom to look for when figuring out the age of old organic matter, for example, some bits of wood found in an old Egyptian tomb. Now, here's a question for all you hotshots out there. Remember, though, that the best estimate of the present age of the universe is the much smaller number of 10 10 years, so for all practical purposes, atoms are forever. Ultimately, even these stable atoms have a limit imposed by the lifetime of proton (>10 25 years). But, in all these cases, the point of the decay is to reach a type of atom that is stable. For different radioactive atoms, this number can be anywhere from a tiny fraction of a second to minutes, hours, days, or even millions of years. For carbon-14, this number is 5,730 years. However one usually works with many, many atoms, and, in that case, one can use a very reliable average time called the" half-life." This is the time that it takes for half (50%) of a bunch of unstable atoms to decay. ![]() The rate at which this happens is a "stochastic" process - it happens when it happens and you can't predict exactly when THAT atom over in the corner there will transform. So now the carbon-14 atom has transformed into a very stable nitrogen atom (which is identified by its 7 protons). Remember that the type of atom is determined by the number of protons. Since the neutron that did this is now a proton, you have 7 protons and 7 neutrons. Every once in a while, a carbon 14 atom emits an electron (and yes, that pesky anti-neutrino too). There is a variety called "carbon-14" which has 8 neutrons. This is called "carbon-12" from the fact that there are 6 protons plus 6 neutrons. The most common (and stable) form has 6 neutrons. Essentially they are special versions of a particular atom that are trying to change to a stable type of atom, that is, one that will NOT change with time. This is an example of a "radioactive" atom. This electron is spat out of the nucleus. What is happening is that one of the neutrons in this neutron-enhanced version of the atom, is changing into a proton plus an electron (plus a zero mass particle called the anti-neutrino, but we can chat about that some other time). Sometimes, when an atom doesn't have the 'right' number of neutrons, it becomes unstable and shoots out sub-atomic particles, a common one being the electron. The number of neutrons is usually fixed for a particular atom (for example, the most common form of carbon has 6 neutrons), but this does not have to be so. So, hydrogen has 1 proton, oxygen has 8 protons, iron has 26 protons, and so on. (This is necessary to keep the electrical charge of the atom zero.) The number of protons determines the identity of the atom. Surrounding the nucleus is a cloud of electrons whose number equals that of the number of protons. Almost all of the mass (the proper word for "weight") of the atom is contained in the nucleus. Atoms are made of a central core containing a collection of protons and neutrons. ![]()
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