Chemical or molecular formula — lesson. Science State Board, Class 8.

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எங்கள் ஆசிரியர்களுடன் 1-ஆன்-1 ஆலோசனை நேரத்தைப் பெறுங்கள். டாப்பர் ஆவதற்கு நாங்கள் பயிற்சி அளிப்போம்

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The chemical formula is the easy notation of a molecule (compound).

It shows the exact number of atoms of each element present in a molecule of a substance.

The following steps are used to write down chemical formula:

Step 1: Place the positive radical on the left and the negative radical on the right while writing the symbols of elements/ions side by side.

Step 2: In superscript, write the valencies of the two radicals to the right of their symbols. (The ions'+' and '-' signs were omitted).

Step 3: The valencies of the elements/ions are interchanged. These numbers should be written as subscripts.

However, the number

$1$ on the symbol's superscript is omitted.

Example:

( $i$ ). Calcium chloride ( $CaCl_2$ ).

1st step: Place the calcium and chlorine symbols side by side.

$Ca$

$Cl$

2nd step: Write the valencies of calcium and chlorine to the right of their symbols.

$Ca^2$

$Cl^1$

3rd step: Interchange the valencies of elements.

$CaCl_2$

The chemical formula of Calcium chloride is (

$CaCl_2$ ).

( $ii$ ). Magnesium chloride ( $MgCl_2$ )

1st step: Place the magnesium and chlorine symbols side by side.

$Mg$

$Cl$

2nd step: Write the valencies of magnesium and chlorine to the right of their symbols.

$Mg^2$

$Cl^1$

3rd step: Interchange the valencies of elements.

$MgCl_2$

The chemical formula of Magnesium chloride is (

$MgCl_2$ ).

( $iii$ ). Sodium hydroxide ( $NaOH$ )

1st step: Place the sodium and hydroxide symbols side by side.

$Na$

$OH$

2nd step: Write the valencies of sodium and hydroxide to the right of their symbols.

$Na^1$

$OH^1$

3rd step: Interchange the valencies of elements.

$NaOH$

The chemical formula of Sodium hydroxide is (

$NaOH$ ).

( $iv$ ). Calcium phosphate ( $Ca_3(PO_4){_2}$ )

1st step: Place the calcium and phosphate symbols side by side.

$Ca$

$PO_4$

2nd step: Write the valencies of calcium and phosphate to the right of their symbols.

$Ca^2$

$(PO_4){_3}$

3rd step: Interchange the valencies of elements.

$Ca_3(PO_4){_2}$

The chemical formula of Calcium phosphate is (

$Ca_3(PO_4){_2}$ ).

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8. Chemical or molecular formula

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