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Ch 4 Section 5-7

Atomic number

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
Created by: tilleryc