2.2 The Periodic Table2.2 The Periodic Table

The Periodic TableThe Periodic Table

Every block represents an elementEvery block represents an element

Every periodic table has a keyEvery periodic table has a key

The Periodic TableThe Periodic Table

Where did the modern periodic table come Where did the modern periodic table come from?from? NewlandsNewlands MendeleyevMendeleyev

Modern Periodic TableModern Periodic Table

Period or SeriesPeriod or Series – a horizontal row of – a horizontal row of elements, numbered 1-7)elements, numbered 1-7)

Group or FamilyGroup or Family – a vertical row of – a vertical row of elements (numbered 1-18 on the modern elements (numbered 1-18 on the modern table) (long ago: roman numerals)table) (long ago: roman numerals)

Modern Periodic TableModern Periodic Table

StaircaseStaircase – divides the metals from the – divides the metals from the nonmetalsnonmetals

MetalloidsMetalloids – look like metals but act like – look like metals but act like nonmetalsnonmetals

The Periodic LawThe Periodic Law

States that when elements are arranged in States that when elements are arranged in order of increasing atomic mass, certain order of increasing atomic mass, certain physical and chemical characteristics physical and chemical characteristics repeat in a regular pattern (periodically)repeat in a regular pattern (periodically)

Modern Periodic TableModern Periodic Table

Atomic MassAtomic Mass – defined relative to the – defined relative to the mass of a carbon atom, which is given a mass of a carbon atom, which is given a mass of 12 amumass of 12 amu

AMUAMU (atomic mass unit) – defined as 1/12 (atomic mass unit) – defined as 1/12 the mass of a carbon atomthe mass of a carbon atom

Period / Group NamesPeriod / Group Names

Group 1 – Alkali MetalsGroup 1 – Alkali Metals Soft, silver colored metals that react violently Soft, silver colored metals that react violently

with waterwith water React with the halogensReact with the halogens

Group 2 – Alkaline Earth MetalsGroup 2 – Alkaline Earth Metals Light, reactive metals that form oxide coatings Light, reactive metals that form oxide coatings

with air exposure (ex MgO, CaO)with air exposure (ex MgO, CaO)

Period / Group NamesPeriod / Group Names

Group 17 – HalogensGroup 17 – Halogens Extremely reactive (F is the most)Extremely reactive (F is the most) Form hydrogen halides (ex HCl)Form hydrogen halides (ex HCl)

Group 18 – Noble GasesGroup 18 – Noble Gases Extremely low chemical reactivityExtremely low chemical reactivity

Period / Group NamesPeriod / Group Names

Transition ElementsTransition Elements Groups 3-12Groups 3-12

Representative ElementsRepresentative Elements Groups 1-2, & 13-18Groups 1-2, & 13-18

* Hydrogen is the exception to almost every * Hydrogen is the exception to almost every rule in chemistryrule in chemistry

The AtomThe Atom

The AtomThe Atom

Is the smallest part of an element that is Is the smallest part of an element that is still representative of that elementstill representative of that element

A neutral particle composed of a nucleus A neutral particle composed of a nucleus (containing protons and neutrons) and (containing protons and neutrons) and electronselectrons

# electrons = # protons# electrons = # protons

ElectronsElectrons

ee--

A small, negatively charged subatomic A small, negatively charged subatomic particleparticle

Has negligible massHas negligible mass

NucleusNucleus

The centre of an atomThe centre of an atom

Contains most of the mass and all of the Contains most of the mass and all of the positive charge of an atompositive charge of an atom

ProtonsProtons

pp++

Positively charged subatomic particlePositively charged subatomic particle

Found in the nucleusFound in the nucleus

Mass of 1 amuMass of 1 amu

NeutronsNeutrons

nn

Uncharged (neutral)Uncharged (neutral)

Found in the nucleusFound in the nucleus

Mass of 1 amuMass of 1 amu

Atomic Number and Atomic MassAtomic Number and Atomic Mass

Atomic NumberAtomic Number The number of protons an atom hasThe number of protons an atom has Different for each elementDifferent for each element

Atomic Mass (Mass Number)Atomic Mass (Mass Number) # protons + # neutrons# protons + # neutrons