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Summary of Chapter 4

Periodic Table of Elements

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4.1 Periodic Table of Elements

Elements are arranged in an increasing orderof their proton numbers in the Periodic Table.

The number of valence electronsdetermines the position of the groupof anelement.

The number of shells occupied withelectronsin the atom of an element gives theposition of the periodof that element.

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4.2 Group 18 Elements (oble

Gases!

oble gaseshave low densities, low

melting and boiling points but they

increase when going down Group !.

"oble gases are chemically inert.

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4." Group 1 Elements (#l$ali

%etals!

#l$ali metalshave low densities which increase when goingdown Group .

#l$ali metals have low melting and boiling points which decreasewhen going down Group .

#l$ali metals are silvery soft solids and good conductors of heatand electricity.

#l$ali metals have similar chemical properties.

The reactivity of al$ali metals increases when going down Group.

#l$ali metals react with water, o%ygen, chlorine or bromine.

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4.4 Group 1& Elements

('alogens!

'alogenshave low densities, low melting andboiling points but they increase when going downGroup &.

#ll halogens have similar chemical properties.

The reactivity of halogens decreases when goingdown Group &.

'alogens react with water, iron and sodiumhydro%ide solution.

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4. Elements in a Period

(hen going across Period "of the Periodic Table . . .

The atomic radius of elements decreases.

The electronegativity of element increases.

The metallic property of elements decreases.

The physical state of elements changes from solid to gas.

The properties of o%ides of the elements change from basic,amphoteric to acidic.

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4.) Transition Elements

Transition elements are metals that e%hibit metallicproperties such as ductile, malleable, high tensilestrength, high melting and boiling points, highdensities, good conductors of heat and electricity.

Transition elements have special characteristicssuch as)

*orm coloured ions or compounds.

E%hibit different o%idation numbers in their compounds.

*orm comple% ions.

#ct as catalysts in certain reactions.