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The Periodic Law– Similar physical and chemical properties recur

periodically when the elements are listed in order ofincreasing atomic number.

– Each period ends with a completely filled outer shellthat has the maximum number of electrons for thatshell.

– The number identifying the A families identifies thenumber of electrons in the outer shell, excepthelium.

– The outer shell electrons are responsible forchemical reactions.

– Group A elements are called representativeelements.

– Group B elements are called transition elements.

ns1

ns2

ns2 n

p1

ns2 n

p2

ns2 n

p3

ns2 n

p4

ns2 n

p5

ns2 n

p6

d1

d5 d10

4f

5f

Ground State Electron Configurations of the Elements

The horizontal rows of the periodic tableare called PERIODS.

The vertical columns of the periodic tableare called GROUPS, or FAMILIES.

The elements in any groupof the periodic table havesimilar physical and chemicalproperties!

Alkali Metals

Alkaline Earth Metals

Transition Metals

InnerTransition Metals

These elements are alsocalled the rare-earth

elements.

Halogens

Noble GasesThe Inert (Noble) Gases

The six noble gases, He, Ne, Ar, Kr, Xe, and Rn, rarely enter intochemical reactionsAll have complete octets ...= stability!

Periodic RelationshipsThe valence shell is the outermost occupied shell

The period number = principal quantumnumber, n, of the electrons in the valence shell

Periodic RelationshipsFor main group elements the number of valence shellelectrons is the same as the periodic table “A” groupnumber

Families Periods

• Columns of elements arecalled groups or families.

• Elements in each familyhave similar but notidentical properties.

• For example, lithium (Li),sodium (Na), potassium(K), and other members offamily IA are all soft, white,shiny metals.

• All elements in a familyhave the same number ofvalence electrons.

• Each horizontal row ofelements is called a period.

• The elements in a periodare not alike in properties.

• In fact, the propertieschange greatly across evengiven row.

• The first element in aperiod is always anextremely active solid. Thelast element in a period, isalways an inactive gas.

Metals, Nonmetals, andMetalloids

Metals have a small number of electrons in theirvalence shells and tend to form positive ions

Except for hydrogenand helium, all s-blockelements are metals

All d- and f-blockelements are metals

Metals, Nonmetals, andMetalloids

Atoms of a nonmetal generally have larger numbers of electronsin their valence shell than do metals, and many tend to formnegative ions

Nonmetals are all p-block elements andinclude hydrogen andhelium

Metalloids haveproperties of bothmetals and nonmetals

Metal: Elements that are usually solids at roomtemperature. Most elements are metals.

Non-Metal: Elements in the upper right corner of theperiodic Table. Their chemical and physical properties aredifferent from metals.

Metalloid: Elements that lie on a diagonal line betweenthe Metals and non-metals. Their chemical and physical properties are intermediate between the two.

Properties of Metals

• Metals are good conductorsof heat and electricity.

• Metals are shiny.• Metals are ductile (can be

stretched into thin wires).• Metals are malleable (can be

pounded into thin sheets).• A chemical property of metal

is its reaction with waterwhich results in corrosion.

Properties of Non-Metals

• Non-metals are poorconductors of heat andelectricity.

• Non-metals are notductile or malleable.

• Solid non-metals arebrittle and break easily.

• They are dull.• Many non-metals are

gases.

Sulfur

Properties of Metalloids

• Metalloids (metal-like) haveproperties of both metals andnon-metals.

• They are solids that can beshiny or dull.

• They conduct heat andelectricity better than non-metals but not as well asmetals.

• They are ductile andmalleable.

Silicon

SymbolAtomic Mass

Atomic Number

Charge (if ion)

Atomic Number, ZAtomic Number, ZAll atoms of the same elementAll atoms of the same element

have the same number ofhave the same number of

protons in the nucleus, protons in the nucleus, ZZ

1313

AlAl

26.98126.981

Atomic numberAtomic number

Atom symbolAtom symbol

AVERAGE Atomic MassAVERAGE Atomic Mass

Mass Number, AMass Number, A•• C atom with 6 protons and 6 neutrons isC atom with 6 protons and 6 neutrons is

the mass standardthe mass standard•• = 12 atomic mass units= 12 atomic mass units•• Mass NumberMass Number (A) (A)

= # protons + # neutrons= # protons + # neutrons•• NOT on the periodic tableNOT on the periodic table……(it is the(it is the

AVERAGE atomic mass on the table)AVERAGE atomic mass on the table)•• A boron atom can have A boron atom can have

A = 5 p + 5 n = 10 A = 5 p + 5 n = 10 amuamu

A

Z

10

5B

IsotopesIsotopes

•• Atoms of the same element (sameAtoms of the same element (sameZ) but different mass number (A).Z) but different mass number (A).

•• Boron-10 (Boron-10 (1010B) has 5 p and 5 nB) has 5 p and 5 n

•• Boron-11 (Boron-11 (1111B) has 5 p and 6 nB) has 5 p and 6 n

10B

11B

IONSIONS

•• IONSIONS are atoms or groups of atoms with aare atoms or groups of atoms with a

positive or negative charge.positive or negative charge.

•• Taking awayTaking away an electron from an atom gives a an electron from an atom gives a

CATIONCATION with awith a positive chargepositive charge

•• AddingAdding an electron to an atom gives an an electron to an atom gives an ANIONANIONwith awith a negative chargenegative charge..

HHydrogenHydrogen

1

1

Protons: 1Neutrons: 0Electrons: 1

NaSodiumSodium

23

11

Protons: 11Neutrons: 12Electrons: 11

RheniumRhenium

Re186

75

Protons: 75Neutrons: 111Electrons: 75

Rhenium isotopeRhenium isotope

Re187

75

Protons: 75Neutrons: 112Electrons: 75

EXAMPLE

How many protons, neutrons and electrons are found in an atom of

13355 Cs

Atomic number = protons and electronsThere are 55 protons and 55 electrons

Mass number = sum of protons and neutrons133 – 55 = 78There are 78 neutrons

Describe how to read the periodictable:

• Every table has:

Describe how to read the periodic table:

Atomic Mass:The atomic mass is the average mass of an element in atomicmass units ("amu").

Though individual atoms always have a whole number of amus,the atomic mass on the periodic table is shown as a decimalnumber because it is an average of all the isotopes of anelement.

Atomic NumberThe number of protons in an atom identifies the element. The number of protons in an atom is referred to as theatomic number of that element.

Atomic Symbol:The atomic symbol is one or two letters chosen to represent anelement ("H" for "hydrogen," etc.). These symbols are used every where in the world Usually, a symbol is the abbreviation of the element or theabbreviated Latin name of the element.

We can deduce the general form of electronconfigurations directly from the periodic table

Sub-Levels

Electron Configurations and theElectron Configurations and thePeriodic TablePeriodic Table

• The periodic table can be used as a guidefor electron configurations.

• The period number is the value of n.

• Groups 1A and 2A have the s-orbital filled.

• Groups 3A - 8A have the p-orbital filled.

• Groups 3B - 2B have the d-orbital filled.

• The lanthanides and actinides have the f-orbital filled.