Atomic Structure

Atomic Structure - Atomic number - # of proton in the...

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Atomic number - # of proton in the nucleus Example: Be 4 means that Beryllium has four protons Mass number – protons + neutrons 9 4 Be is the convention; or we can write Beryllium-9 Isotopes – same atomic number (same # protons), different mass numbers - Different number of neutrons Atomic weight – weighted average of the masses of naturally occurring isotopes Electrons held by an atom can exist only at discrete energy levels; they are quantized Principal quantum number – can be anything from 1-7 Subshell quantum number – s, p, d or f 0, 1, 2 or 3 Orbital number – described by examples: in the s orbital, we have just 0. In the p orbital, we have 3 possible orbitals: -1, 0 or 1. In the d orbital, we have five: -2, -1, 0, 1 or 2…etc. Spin number: either positive or negative 1/2 The block in the periodic table tells us in which subshell the valence electrons of the atom will be. - Anomalies: the d block starts at n=3 - The f blocks starts at n=4. - Some atoms gain stability when they have a half-filled d subshell - Chromium’s electron configuration: [Ar] 4s 1 3d 5 - Molybdenum and Tungsten are similar - Copper, silver and gold also have half-filled s subshells because they are more stable
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Atomic Structure - Atomic number - # of proton in the...

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