Search results
Results from the WOW.Com Content Network
Almost all of the mass of an atom is located in the nucleus, with a very small contribution from the electron cloud. Protons and neutrons are bound together to form a nucleus by the nuclear force. The diameter of the nucleus is in the range of 1.70 fm (1.70 × 10 −15 m [7]) for hydrogen (the diameter of a single proton) to about 11.7 fm for ...
Its mass is slightly less than the mass of a neutron and approximately 1836 times the mass of an electron (the proton-to-electron mass ratio). Protons and neutrons, each with a mass of approximately one atomic mass unit, are jointly referred to as nucleons (particles present in atomic nuclei). One or more protons are present in the nucleus of ...
Conversely, if it has more protons than electrons, it has a positive charge and is called a positive ion (or cation). The electrons of an atom are attracted to the protons in an atomic nucleus by the electromagnetic force. The protons and neutrons in the nucleus are attracted to each other by the nuclear force. This force is usually stronger ...
Since protons and neutrons behave similarly within the nucleus, they are both referred to as nucleons. Nucleons have a mass of approximately one atomic mass unit, or dalton (symbol: Da). Their properties and interactions are described by nuclear physics. Protons and neutrons are not elementary particles; each is composed of three quarks.
For example, uranium-238 usually decays by alpha decay, where the nucleus loses two neutrons and two protons in the form of an alpha particle. Thus the atomic number and the number of neutrons each decrease by 2 ( Z : 92 → 90, N : 146 → 144), so that the mass number decreases by 4 ( A = 238 → 234); the result is an atom of thorium-234 and ...
For premium support please call: 800-290-4726 more ways to reach us
The heaviest stable element, lead (Pb), has many more neutrons than protons. The stable nuclide 206 Pb has Z = 82 and N = 124, for example. For this reason, the valley of stability does not follow the line Z = N for A larger than 40 ( Z = 20 is the element calcium ). [ 3 ]
There is a general trend of increasing stability for isotopes with a greater neutron excess (N − Z, the difference in the number of protons and neutrons), especially in elements 110, 112, and 114, which strongly suggests that the center of the island of stability lies among even heavier isotopes.