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

Metals, Metalloids, and Nonmetals

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

Groups on the Periodic Table

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.

Ionization energy

Electron Configuration and Ionization Energy

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