IIIIII Periodic Trends The Periodic Table

Periodic Law zWhen elements are arranged in order of increasing atomic #, elements with similar properties appear at regular intervals.

zSame number of valence electrons = similar properties Li 1s 2 2s 1 Na 1s 2 2s 2 2p 6 3s 1 zIn any group, the element BELOW has one more occupied energy level than does the element ABOVE. zThe period that an element is in is the same as the energy level that its valence electrons are in. Li  in 2 nd periodNa  in 3 rd period val. e- in 2 nd val e- in 3rd

Metallicity More Metallic Less Metallic More Metallic Less Metallic

Periodic Trends and Factors zThere are trends in properties of elements y left right AND up down trends zTrends yAtomic Radius yIonic Radius yIonization Energy yElectronegativity zFactors: Columbic attraction and Sheilding effect

IIIIII Periodic Factors

Coulombic attraction depends on… 2– 2+ 2– 1– 2– amount of chargedistance between charges + + – – H He + – + – + – As we go, more coulombic attraction, no new energy level, more pull, smaller size

shielding effect: kernel e – “shield” valence e – from attractive force of the nucleus Li v.e – K -- caused by kernel and valence e – repelling each other As we go, shielding effect increases. tougher to remove easier to remove

IIIIII Atomic Radius

zThe size of a neutral atom z Increases as we go down yWhy? xAdd a new energy level each time (larger orbitals) zDecreases as we go across yWhy? xIt has do to with coloumbic attraction (attraction between + and -)

Atomic Radius Li Na K Rb Cs Cl S P Si Al Br Se As Ge Ga I Te SbSn In Tl Pb Bi Mg Ca Sr Ba Be F O N C B IA IIA IIIA IVA VA VIA VIIA

yDecreases to the LEFT and increases DOWN Atomic Radius

zWhich atom has the larger radius? yBe orBa yCa orBr Ba Ca Examples

IIIIII Ionic Radius

zIonic Radius yCations (+) xlose e - xsmaller © 2002 Prentice-Hall, Inc. yAnions (–) xgain e - xlarger Ionic Radius

zAs you go down, the ionic radius increases due to more energy levels. zAs you go across yThe ionic radius of metals decreases until middle of periodic table, slight increase, and then decrease. yDue to lose or gain of electron

zWhich particle has the larger radius? ySorS 2- yAlorAl 3+ S 2- Al Examples

IIIIII Ionization Energy

zThe energy required to remove an electron from an atom. zEach successive ionization requires more energy than the previous one. zAs we go down, the first ionization energy decreases (due to shielding). zAs we go across, the first ionization energy increases.

zSuccessive Ionization Energies yMg1st I.E.736 kJ 2nd I.E.1,445 kJ Core e - 3rd I.E.7,730 kJ yLarge jump in I.E. occurs when a CORE e - is removed. Ionization Energy

yAl1st I.E.577 kJ 2nd I.E.1,815 kJ 3rd I.E.2,740 kJ Core e - 4th I.E.11,600 kJ zSuccessive Ionization Energies yLarge jump in I.E. occurs when a CORE e - is removed. Ionization Energy

zWhich atom has the higher 1st I.E.? yNorBi yBa orNe N Ne Examples

IIIIII Electronegativity

zTendency of an atom to attract electrons in a chemical bond. yExcludes noble gases. zAs you go down, electronegativity decreases. zAs you go across, the electronegativity increases.

Electronegativity zWhy smaller going down? yThe higher the energy level, the less the electron attraction of the atom. zWhy larger going across? yAs the number of valence electrons increases, the electron attraction of the atom increases.

Electronegativity zValues yLowest values– metals at the far left xLose electrons yHighest values – nonmetals at the far right xGain electrons

IIIIII Other Periodic Trends

zMelting/Boiling Point yHighest in the middle of a period. Melting/Boiling Point

zWhich atom has the higher melting/boiling point? yLiorC yCrorKr C Cr Examples

IIIIII Summary Let’s Recap Let’s Recap

Summary of Periodic Trends Ionic size (cations) Ionic size (anions) decreases Shielding is constant Atomic radius decreases Ionization energy increases Electronegativity increases Shielding increases Atomic radius increases Ionic size increases Ionization energy decreases Electronegativity decreases 1A 2A3A4A 5A 6A7A 0