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Ch 4 Section 5-7
Atomic number
Question | Answer |
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Atomic Number | The atomic number is equal to the number of protons in the nucleus. Sometimes given the symbol Z. On the periodic table Z is the uppermost number in each element’s box. |
Moseley | realized that the atomic number determines the element. The elements differ from each other by the number of protons in the nucleus. The number of electrons in a neutral atom is also equal to the atomic number |
Neutrons and James Chadwick | analyzed the results of -particle scattering on thin Be films. Chadwick recognized existence of massive neutral particles which he called neutrons. Chadwick discovered the neutron. |
Mass Number | Mass number is given the symbol A. A is the sum of the number of protons and neutrons. Z = proton number N = neutron number A = Z + N A common symbolism used to show mass and proton numbers is (nuclide symbol) AZC A-Z=number of neutrons |
Isotopes | are atoms of the same element but with different neutron numbers. Isotopes have different masses and A values but are the same element. Example of an isotopic series is the hydrogen or oxygen isotopes. |
Moseley stated | each element differs from the preceding element by having one more positive charge in its nucleus |
Chadwick | atoms consist of very small, very dense nuclei surrounded by clouds of electrons at relatively great distances from the nuclei. All nuclei contain protons; nuclei of all atoms except the common form of hydrogen also contain neutrons |
Isotopes | are atoms of the same element with different masses; they are atoms containing the same number of protons but different numbers of neutrons |
Mass number | # of protons + # of neutrons atomic number + neutron number |