THE PERIODIC TABLE

PERIODIC When something occurs at regular intervals (you can predict what happens / comes next)

So what makes the periodic table periodic? ATOMIC NUMBER!!! (across the chart)

PERIODIC LAW The properties of the elements are a periodic function of their atomic numbers

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All of the elements in a horizontal row PERIOD All of the elements in a horizontal row

All of the elements in a vertical column (aka Family) GROUP All of the elements in a vertical column (aka Family)

invented the periodic table based on increasing atomic mass Dmitri Mendeleev (1834-1907) invented the periodic table based on increasing atomic mass …and yes, he too, is your friend

revised the periodic table based on properties and Henry Moseley (1913) revised the periodic table based on properties and atomic number …and yes, he too, is your friend

ALKALI METALS s1 group Good Conductors

ALKALINE EARTH METALS Group 2 Harder, more dense, stronger than alkali

TRANSITION METALS Groups 3-11

LANTHANOID SERIES 4f sub energy level Z = 57-70

ACTINOID SERIES 5f sub energy level Z = 89-102 All have radioactive forms (unstable p+ & N°)

13, 14, 15, 16 are named by the first element in the column Columns 13, 14, 15, 16 are named by the first element in the column (e.g. Boron Group)

HALOGENS Group 17 Combine with metals to form salts Very reactive

NOBLE GASES Group 18 Inert gases (not reactive) 8 valence electrons

Stability of e-configurations

The eight outer electrons in an atom OCTET The eight outer electrons in an atom

Atoms with full outer energy levels are very stable (less reactive) FACT: Atoms with full outer energy levels are very stable (less reactive)

OCTET RULE If an atom has 8 electrons in its outer energy level, it is unreactive (except He, which is full at 2).

Now…how do we make ENERGY LEVELS more stable?

Ways to make full outer energy levels: Add electrons to a partially filled outer energy level Lose all electrons in the outer energy level Share electrons with another atom

Periodic Trends

ATOMIC RADIUS The distance from the center of the nucleus to the outermost energy level

The atomic radius INCREASES within a family (just adding energy levels)

The atomic radius DECREASES within a period (more positive charge pulling e-)

SHIELDING EFFECT The positive pull is less because the distance between nucleus and electrons is greater

IONIZATION ENERGY the energy required to remove an electron from an atom

The ionization energy DECREASES as you go down a family (shielding effect)

The ionization energy INCREASES across a period (more p+ have more pull on e-)

ELECTRON AFFINITY how much an atom desires another electron

The electron affinity DECREASES as you go down a family (shielding effect)

(more p+ have more pull on e-) The electron affinity INCREASES across a period (except for the noble gases) (more p+ have more pull on e-)

ELECTRONEGATIVITY The tendency of an atom to attract electrons to itself when it is bonded to another atom

The electronegativity DECREASES as you go down a family (shielding effect)

The electronegativity INCREASES across a period (more p+ have more pull on e-)