The Periodic TableThe Periodic Table

The most important document The most important document in chemistryin chemistry

Learning objectivesLearning objectives

Define group and period as related to Define group and period as related to periodic tableperiodic table

Describe properties of metal, semi-Describe properties of metal, semi-metal and nonmetalmetal and nonmetal

Write names and symbols of several Write names and symbols of several common elementscommon elements

Predict type of element from position in Predict type of element from position in periodic tableperiodic table

Elements: names and symbolsElements: names and symbols

All elements have a name and a All elements have a name and a symbol (one or two letters)symbol (one or two letters)

Symbols are used in writing compound Symbols are used in writing compound formulae and chemical equationsformulae and chemical equations

It is essential to be familiar with both It is essential to be familiar with both names and symbols for the important names and symbols for the important elementselements

Common elements and Common elements and symbols - obvioussymbols - obvious

CarbonCarbon CalciumCalcium ChlorineChlorine NitrogenNitrogen OxygenOxygen AluminiumAluminium PhosphorousPhosphorous

Common elements and Common elements and symbols – less obvioussymbols – less obvious

SodiumSodium PotassiumPotassium IronIron MercuryMercury SilverSilver GoldGold TungstenTungsten

18691869Dimitri Mendeleev developed Dimitri Mendeleev developed

the periodic table the periodic table Ordered elements according to atomic Ordered elements according to atomic

weights and physical and chemical weights and physical and chemical properties. properties.

Only about 60 elements had been Only about 60 elements had been identifiedidentified

Predicted existence of as-yet-Predicted existence of as-yet-undiscovered elements and their undiscovered elements and their properties. Predictions often proved properties. Predictions often proved astonishingly accurate.astonishingly accurate.

The modern periodic tableThe modern periodic tableThere are 92 naturally occurring elements: 2 There are 92 naturally occurring elements: 2

liquids, 11 gases, 23-25 nonmetalsliquids, 11 gases, 23-25 nonmetals

Reduce chemistry of all elements Reduce chemistry of all elements to discussion of group behaviourto discussion of group behaviour

1A ALKALI METALS: Reactive. 1A ALKALI METALS: Reactive. Reactivity increases down group. Reactivity increases down group. Physical properties vary gradually.Physical properties vary gradually.

2A ALKALINE EARTH METALS : 2A ALKALINE EARTH METALS : Similar to alkalis but less reactive. Lots Similar to alkalis but less reactive. Lots of common calcium compounds: of common calcium compounds: calcium carbonate (limestone, marble), calcium carbonate (limestone, marble), calcium oxide (lime), calcium sulphate calcium oxide (lime), calcium sulphate (gypsum, plaster of Paris)(gypsum, plaster of Paris)

Important groups on other side Important groups on other side of tableof table

7A HALOGENS: Very reactive, form lots of 7A HALOGENS: Very reactive, form lots of compounds with most elements. Chlorides in compounds with most elements. Chlorides in particular are common: NaCl, KCl. Reactivity particular are common: NaCl, KCl. Reactivity decreases down groupdecreases down group

8A RARE, INERT, NOBLE GASES: Discovered 8A RARE, INERT, NOBLE GASES: Discovered late because of lack of compounds, all gases. Not late because of lack of compounds, all gases. Not “rare” since 1 % argon in air; He second most “rare” since 1 % argon in air; He second most abundant element in universe. Very unreactive. abundant element in universe. Very unreactive. Provide insight into properties of other elementsProvide insight into properties of other elements

The Periodic Table: two main The Periodic Table: two main

types of element: metals -types of element: metals - are are shiny, lustrous; good conductors of shiny, lustrous; good conductors of

heat and electricity. Only one metal is a heat and electricity. Only one metal is a liquid at room temp.liquid at room temp.

The Periodic Table: non-The Periodic Table: non-metals -metals - insulators (or perhaps insulators (or perhaps

semiconductors), poor heat conductors semiconductors), poor heat conductors mostly. Solids are brittle. Several are mostly. Solids are brittle. Several are

gases, one is a liquid.gases, one is a liquid.

The Periodic Table: semi-The Periodic Table: semi-metals – borderline casesmetals – borderline cases

Some properties are metal-likeSome properties are metal-like Other properties are nonmetal-likeOther properties are nonmetal-like

SemiconductorsSemiconductors

Atoms and ionsAtoms and ions

Ions are charged particles with more or Ions are charged particles with more or less electrons than protonsless electrons than protons

Positive ion (cation) has fewer Positive ion (cation) has fewer electronselectrons

Negative ion (anion) has more Negative ion (anion) has more electronselectrons

Ions and compoundsIons and compounds

Ions are important in one class of Ions are important in one class of compoundscompounds

Metals form positive ionsMetals form positive ions Nonmetals form negative ionsNonmetals form negative ions Periodic table can be used to predict Periodic table can be used to predict

chargescharges

Rules to predict ion chargeRules to predict ion charge

CationCation Charge = group numberCharge = group number

AnionAnion Charge = - (8 - group number)Charge = - (8 - group number)

Practice with a few examplesPractice with a few examples