Periodicity - PERIODIC TABLE Arranged by ATOMIC NUMBER This...

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PERIODIC TABLE Arranged by ATOMIC NUMBER This is the nmber of protons in the nucleus This is also the number of electrons in the atom. ATOMIC WEIGHT is the average weight of the atom in amu (atomic mass units => g/mole)
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All atoms of a given element have the same number of protons and electrons. Different isotopes of an element have different numbers of neutrons and therefore different masses. Examples of isotopes: 1 H 2 H (=D) 3 H (=T) 99.985% 0.015% 0% natural abundances. 35 17 Cl 37 17 Cl or just 35 Cl 37 Cl 75.77% 24.23% Average atomic weight = 0.7577 x 35 + 0.2423 x 37 = 26.5 + 9.0 amu = 35.5 amu ISOTOPES
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Periods go across 1st period: H-He 2nd period: Li-Ne 3rd period: Na-Ar Groups go down 1st group: Alkali metals 2nd group: Alkaline earth metals
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Periodicity Periodic Trends Size Ionization energy and Electron affinity Electronegativity Metallic Character Trends in Acid/base properties Trends in Oxidation states 5 Periodicity
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Sizes of Atoms 6 Periodicity Atomic radii increase with increasing electron shielding . Atomic radii decrease with increasing effective nuclear charge .
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Sizes of Ions Ionic size Cations have smaller radii than their parent atoms. Anions have larger radii than their parent atoms. 7
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Sizes of atoms and ions Even though cations have smaller radii and anions have larger radii than neutral atoms, the periodic trends in size are still valid for both atoms and ions. 8
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Ionization energy (IE) is the energy necessary to remove an electron from an atom, molecule or ion. Moving down a group, ionization energy decreases because of increased electron shielding. Moving across a row from left to right ionization energy increases because of increased effective nuclear charge . IONIZATION ENERGY
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Moving down a group, IE decreases because of increased electron shielding. Moving across a row from left to right, IE increases because of increased effective nuclear charge. It is easier to remove an electron from a 2p orbital than it is to remove
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Periodicity - PERIODIC TABLE Arranged by ATOMIC NUMBER This...

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