History of the Periodic History of the Periodic TableTable Dimitri Mendeleev published Dimitri Mendeleev published

a periodic table that a periodic table that arranged elements by arranged elements by increasing increasing atomic massatomic mass

This did not accurately group This did not accurately group elements by similar elements by similar propertiesproperties

The modern table is arranged The modern table is arranged by increasing by increasing atomic numberatomic number

Periodic Law – there is a Periodic Law – there is a periodic repetition of physical periodic repetition of physical and chemical properties and chemical properties when elements are arranged when elements are arranged by increasing atomic numberby increasing atomic number

Some of Medeleev’s work (1869)

Periodic Table (a review)Periodic Table (a review) Groups go down the Groups go down the

tabletable

Elements in the same Elements in the same group have similar group have similar propertiesproperties

Periods go across the Periods go across the tabletable

Chemical properties of Chemical properties of the elements change in the elements change in a predictable manner a predictable manner going across a periodgoing across a period

Periodic Table review Periodic Table review (cont)(cont) Group 1A – alkali metalsGroup 1A – alkali metals

Group 2A – alkaline earth metalsGroup 2A – alkaline earth metals

Group 6A - chalcogensGroup 6A - chalcogens

Group 7A – halogensGroup 7A – halogens

Group 8A – noble gasesGroup 8A – noble gases

Metals are to the left of the staircaseMetals are to the left of the staircase

Non-metals are to the right of the staircaseNon-metals are to the right of the staircase

Metalloids are along the staircase (B, Si, Ge, As, Sb, Te, Po)Metalloids are along the staircase (B, Si, Ge, As, Sb, Te, Po)

Periodic TrendsPeriodic Trends

Atomic radiusAtomic radius

Ionization energyIonization energy

ElectronegativityElectronegativity

Atomic RadiusAtomic Radius The size (radius) of The size (radius) of

an atom of that an atom of that elementelement

Increases moving Increases moving down a groupdown a group

Decreases moving Decreases moving from left to right from left to right across a periodacross a period

Ionization EnergyIonization Energy Amount of energy Amount of energy

needed to remove an needed to remove an ee-- from an atom to from an atom to form an ionform an ion

Decreases moving Decreases moving down a groupdown a group

Increases moving Increases moving from left to right from left to right across a periodacross a period

IONS --> Atoms with a IONS --> Atoms with a chargecharge

3+

3+3-

0 charge

Lithium Atom

2-

+1 charge

Lithium Ion

The ionization energyis the amount of energyneeded to remove this e-

Octet rule and ionsOctet rule and ions

Atoms with a filled outer Atoms with a filled outer energy level (stable energy level (stable octet) are more stableoctet) are more stable

Atoms lose/gain Atoms lose/gain electrons in an effort to electrons in an effort to obtain a filled outer obtain a filled outer energy level.energy level.

Anions (- ions) form by Anions (- ions) form by an atom gaining ean atom gaining e--

Cations (+ ions) form by Cations (+ ions) form by an atom losing ean atom losing e--

Group Charge of most common ion

1A +1

2A +2

3A +3

4A +4, -4

5A -3

6A -2

7A -1

8A Usually do not form ions

ElectronegativityElectronegativity The ability of an The ability of an

atom to attract atom to attract electrons in a electrons in a chemical bondchemical bond

Increases moving Increases moving from left to right from left to right across a periodacross a period

Decreases going Decreases going down a groupdown a group