Particles, subatomic electric charges

The observation that atoms of a single element can have different masses helped scientists refine the nuclear model still further. They realized that an atomic nucleus must contain subatomic particles other than protons and proposed that it also contains electrically neutral particles called neutrons (denoted n). Because neutrons have no electric charge, their presence does not affect the nuclear charge or the number of electrons in the atom. However, they do add substantially to the mass of the nucleus, so different numbers of neutrons in a nucleus give rise to atoms of different masses, even though the atoms belong to the same element. As we can see from Table B.l, neutrons and protons are very similar apart from their charge they are jointly known as nucleons. 

Neutron a nuclear subatomic particle carrying no electrical charge. 

The forces that bond atoms together to form molecules come from tiny, subatomic particles called protons and electrons. These particles have different electrical charges that attract each other. 

The proton, p, has a mass of 1.007277 u and a unit charge of +1. This charge is equal to 1.6022 x 10 19 coulombs a coulomb is the amount of electrical charge involved in a flow of electrical current of 1 ampere for 1 sec. The neutron, n, has no electrical charge and a mass of 1.008665 u. The proton and neutron each have a mass of essentially 1 u and are said to have a mass number of 1. (Mass number is a useful concept expressing the total number of protons and neutrons, as well as the approximate mass, of a nucleus or subatomic particle.) The electron, e, has an electrical charge of -1. It is very light, however, with a mass of only 0.000549 u, about 1/1840 that of the proton or neutron. Its mass number is 0. The properties of protons, neutrons, and electrons are summarized in Table 1.1. 

Proton—a positively charged particle located in the atom s nucleus. The electrical charge has a magnitude of+ 1.6 X 10 19 coulombs (C) however, for simplicity, it is often referred to by its relative charge of +1.0 (charge relative to an electron). The mass of a proton is about 1.67 X 10 24 g. The gram is not a practical unit to describe the mass of subatomic particles, so instead we use the atomic mass unit, or amu. An amu is defined as the mass of a carbon atom containing 6 protons and 6 neutrons. The mass of a proton is 1.0073 amu. 

Atoms themselves are made up of even smaller particles. These subatomic particles are protons, neutrons, and electrons. Protons and neutrons cluster together to form the central core, or nucleus, of an atom. Fast-moving electrons occupy the space that surrounds the nucleus of the atom. As their names imply, subatomic particles are associated with electrical charges. Table 2.1 and Figure 2.2 summarize the general features and properties of an atom and its three subatomic particles. 

Isotopes—Two or more forms of the same element, whose atoms differ from each other in the number of neutrons contained in their nuclei. Neutron—subatomic particle with a mass of about one atomic mass unit and no electrical charge. 

Neutron— A subatomic particle that carries no electrical charge and that has a mass of zero. 

Neutron— A subatomic particle with no electric charge. 

Fission of uranium-235 occurs when neutrons are fired into the reactor. Neutrons are subatomic particles with no electric charge. They cause uranium-235 to break apart, giving off energy. That energy is then used to make electricity. 

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