formulae writing

8/13/2019 Formulae writing

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Formulae


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Learning outcomes

state the symbols of the elements andformulae of compounds mentioned in thesyllabus

deduce the formulae of compounds fromthe relative numbers of atoms present andvice versa

deduce the ionic compounds from thecharges on the ions present and vce versa


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Stating the symbols of elements

Each element is represented by its ownchemical symbol .

Why do elements need to berepresented by symbols?

Chemical symbols make it easierfor chemists to represent theelements in a clear and simple way.


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Stating the symbols of elementsfirst letteronly

first twoletters

first and thirdletter

from theLatin name

Boron B Cobolt Co Zinc Zn Copper Cu

Carbon C Helium He Chlorine Cl (Cuprum)

Iodine I eon e !a"nesium !" Iron Fe

#ul$ur %r"on !an"anese (Ferrum)

ic&el Chromium #odium

Barium ( atrium)

%r

i

Ba

!n

Cr a

#


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Writin" the $ormulae o$ compounds

Every chemical compound is representedby a chemical formula .

determined e'perimentally

or

usin" a list o$ ions


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sodium chloride

Write the $ormula o$the positi e ion $irst

$ollowed by thene"ati e ion.

a * C l +


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What would the $ormulabe?

sodium chloride

a * C l +


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ma"nesium o'ide


$ollowed by the

ne"ati e ion.

!" * / +


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ma"nesium o'ideFormula of a

compound does not carry any charges!

!"/

, !" * ion - , / + ion

!" * / +


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Quick heck ..

"rite down thechemical

formula of thefollowing

compounds#

sodium $luoride

copper(II) o'ide

calcium sul$ide

potassium chloride


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calcium chloride


$ollowed by the

ne"ati e ion.

Ca * C l +


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calcium chlorideFormula of a

compound does not carry any charges! Ca * C l +

CaC l

, Ca * ion - C l + ion


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potassium sul$ide


$ollowed by the

ne"ati e ion.

0 * # +


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potassium sul$ideFormula of a

compound does not carry any charges! 0 * # +

0 #

0 * ion - , # + ion


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aluminium o'ide


$ollowed by the

ne"ati e ion.

%l 1* / +


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aluminium o'ideFormula of a

compound does not carry any charges! %l 1* / +

%l / 1

%l 1* ion - 1 / + ion


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Quick heck ..

"rite down thechemical formula of

the following

compounds#

sodium o'ide

ma"nesium chloride

iron(III) o'ide

2inc chloride

lead (II) iodide

a /

!"C l

Fe /1

ZnC l

3bI


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sodium hydro'ideFormula of a

compound does not carry any charges!

a/H

, a * ion - , /H + ion

a * /H +


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copper (II) sul$ate


$ollowed by the

ne"ati e ion.

Cu * #/ 4 +


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Quick heck ..

"rite downthe chemical

formula of thefollowing

compounds#

calcium carbonate

ma"nesium sul$ate

ammonium chloride

sodium hydro"en+carbonate

CaC/ 1

!"#/ 4

H 4C l

aHC/ 1


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ammonium sul$ate


$ollowed by the

ne"ati e ion.

H 4* #/ 4 +


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ammonium sul$ate$ow about this

compound%H 4* #/ 4 +

( H 4) #/ 4

H 4* ion - , #/ 4 + ion


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aluminium hydro'ide$ow about this

compound%%l 1* /H +

%l (OH) 3

, % l 1* ion - 1 /H + ion


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Quick heck ..

"rite down thechemicalformula of

the following

compounds#

barium nitrate

copper(II) hydro'ide

potassium carbonate

ammonium phosphate

Ba( / 1)

Cu(/H)

0 C/ 1

( H 4)13/ 4

Q i k h k


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Quick heckcompound symbol of

positive ionsymbol of

negative ionFormula

copper &''(o)ide

Cu * / +

*inchydro)ide Zn

*

/H+

sodiumcarbonate

a * a C/ 1

potassiumsulfate #/ 4

+ 0 #/ 4

calciumhydro)ide

Ca * Ca(/H)

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