How do you write ionic formulas for binary compounds?

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How do you write ionic formulas for binary compounds?

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Answer 1 · 2014-05-02T16:23:33

The term binary means two pieces. Binary compounds contain two elements.

Lets take the ionic formula for Calcium Chloride is $C a C l^{2}$ $CaCl^2$

Calcium is an Alkaline Earth Metal in the second column of the periodic table. This means that calcium has 2 valence electrons it readily gives away in order to seek the stability of the octet. This makes calcium a $C a^{+ 2}$ $Ca^(+2)$ cation.

Chlorine is a Halogen in the $17^{t h}$ $17^(th)$ column or $p^{5}$ $p^5$ group.
Chlorine has $7$ $7$ valence electrons. It needs one electron to make it stable at $8$ $8$ electrons in its valence shells. This makes chlorine a $C l^{-}$ $Cl^(− )$ anion.

Ionic bonds form when the charges between the metal cation and non-metal anion are equal and opposite. This means that two $C l^{-}$ $Cl^(−)$ anions will balance with one $C a^{2 +}$ $Ca^(2+)$ cation.

This makes the formula for calcium chloride, $C a C l_{2}$ $CaCl_2$ .

For the example Aluminum Oxide $A l_{2} O_{3}$ $Al_2O_3$

Aluminium has an oxidation state of $+ 3$ $+3$ or $A l^{3 +}$ $Al^(3+)$
Oxygen has an oxidation state of -2 or $O^{2 -}$ $O^(2-)$

The common multiple of 2 and 3 is 6.

We will need 2 aluminum atoms to get a +6 charge and 3 oxygen atoms to get a -6 charge. When the charges are equal and opposite the atoms will bond as $A l_{2} O_{3}$ $Al_2O_3$ .

I hope this is helpful.
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How do you write ionic formulas for binary compounds?

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