Revision_periodicity SL

8/7/2019 Revision_periodicity SL

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KING GEORGE V SCHOOLCHEMISTRY DEPARTMENT

IB REVISIONSTANDARD LEVELTOPIC 3: PERIODICITY 2011


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SHIELDING EFFECTElectron on inner shellsCancel out protons

NUCLEAR CHARGEMore protons in thenucleus attract the

Electrons morestrongly

DISTANCE FROM NUCLEUS


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Across a period the shielding effectSTAYS THE SAME and nuclear charge

INCREASES. This pulls the valenceelectrons closer to the nucleus

DECREASING the atomic radius.Down a group the number of shells

increases. Shielding effect increases.Nuclear charge increases but is further

away, overall decreasing the pulltowards nucleus.INCREASING the atomic radius.


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Down a group the number ofshells increases.

Shielding effect increases.Nuclear charge increases but isfurther away, overall decreasing

the pull towards nucleus.

INCREASING the atomic radius.


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SHIELDING EFFECTElectron on inner shellsCancel out protons

NUCLEAR CHARGEMore protons in thenucleus attract the

Electrons morestrongly

DISTANCE FROM NUCLEUS


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Metallic Bonding


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Valence electrons are delocalised throughout the structure.

They are attracted to the positive metal ion left behind.

Forms a tightly packed lattice with each ion attracted to many

electrons at one time. It is a strong attractive FORCE toovercome so melting and boiling points will be HIGH.


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INCREASE IN CHARGE DENSITY

The nuclei of the atoms are getting more

positively charged.

The "sea of electrons is getting more negativelycharged.

The "sea of electrons is getting progressivelynearer to the nuclei (as the more positivenucleus pulls the other shells in closer) and somore strongly attracted.


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Covalent Bonding tetrahedral structure


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Silicon is MACROMOLECULAR. Each

silicon atom is tetrahedrally bonded to4 other silicons by a covalent bond. Alot of energy is needed to break all

these bonds high melting and boiling

points.


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Van der Waals simple molecules


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The molecules in these structures areNOT bonded together but weakly held

together by van der waals forces.These are instantaneous attractionsbetween the electrons and nucleus of

different atoms.


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The more atoms in a molecule thestronger the Van der Waals attraction

as there are more electrons in themolecule. S8, P4, Cl2

Argon comes in single atoms chance ofVan der Waals attraction is very small.


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Answer thesequestions on

A3 paper.


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Whatarethe 3 thingsyou MUST INCLUDE

ina questionabouttrendsinionisation

energy oratomicradius?


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Complete this table using arrows!

Across aPeriod

Down aGroup

Nuclear Charge/ No.of protons

Shielding Effect

Distance from nucleus

Ionisation Energy


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Which element in the periodic

table would you expect tohave the

- BIGGEST ionisation energy

- SMALLEST ionisation energy

Why?


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Draw a Sodium atom and aSodium ion.

Which is going to be smaller

and WHY (3 marks).


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Match name to picture to description

A: CovalentBonding

B: Van derWaals Forces

C: MetallicBonding

1

2

3

X : Instantaneousdipole

attraction very weak

Y: Strong attractionbetween ion and

delocalised electrons

Z : Strong bondbetween atoms

by sharingelectrons


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Why doesaluminium haveahigher melting pointthan

sodium?

Why doessiliconhavethehighest melting point?

Why does Sulphurhaveahigher melting pointthan

Chlorine?


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Make sure you have completed therevision questions booklet you were

given.

Good luck on Monday!

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Revision_periodicity SL