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Mendeleev
• Made periodic table based on atomic mass and other properties. (especially chemical)
• Had blank spots for undiscovered elements• Called periodic because properties repeat
periodically. (Periodic law)
Henry Mosely
• Discovered nuclear charge.• Gives the “atomic number.”• Fixes Mendeleev’s periodic table.
Periodic Table
• Organized based on properties of elements• Not all periodic tables have the same
information• Shape determined by electronic structure of
atom• Properties occur in a repeating pattern
Properties of Metals
• Conduct electricity• Conduct heat• Malleable • Ductile• Have luster or sheen
tend to make cations by losing electrons
• Non Metals opposite properties of metals–Tend to make anions by gaining
electrons
• Metalloids properties in between metals and nonmetals
Periodicity• The properties of elements repeat in a regular
pattern. (groups) This is periodic law.• Elements are grouped according to properties• Pattern is related to electron configuration.– Group 1 metals all have the same last term in their
electron configuration.Li 2s1 F 2s2, 2p5
Na 3s1 Cl 3s2, 3p5
K 4s1 Br 4s2, 4p5
Rb 5s1 I 5s2, 5p5
Periodic properties
• Atomic radius• Ionization energy• Ionic radius• Electronegativity• Nuclear charge• Shielding
Nuclear Charge
The positive charge on the nucleus. (atomic number) Determined by Henry Moseley
in 1913
Trend:Decreases from bottom to top of group.Increases from left to right in a period
Shielding
The effect of the surrounding electrons on the nuclear charge. Less shielding causes electrons to be held more tightly.
Trend:Decreases from bottom to top of a group Constant across a period
Atomic radius
Defined as ½ the distance between the nuclei of 2 atoms of an element when bonded together
Trend: decreases from bottom to top of a groupDecreases from left the right across period
Ionization energy
The amount of energy required to remove an electron from a neutral atom in the gas phase
Trend: Increases from bottom to top in a group.Increases from left to right across a period.
Ionic radiusThe radius of the ion in a crystal lattice
Trend:Decreases from bottom to top of a group.Decreases for cations across the period. Cations are smaller then the neutral atom.Decreases for anions across the period. Anions are larger than the neutral atom.
Cations Anions
ElectronegativityThe ability of a nucleus to attract the electrons in a bond
Trend:Increases from bottom to top of a group.Increases from left to right across a period