How to write a chemical formula?
As you know that k elements are represented by symbols like that compounds are represented by chemical formulae.Jis trha se hm elements ko symbols k zreay show krte hn isi trha compounds ko likhne k liay hm chemical formula likhte hn.
To write chemical formula following steps would be kept in mind.
1. In chemical formula of compound symbols of elements are written side-by-side, in the order of positive ion first and then negative ion.
Chemical formula me majood elements ko un k symbols se zahir kiya jata ha, jis me positive charge wale ion phle or negative charge wale ion ko bad me likha jata ha.
2. The valencies of each ion is written on the top right corner of its symbol, e.g, Ca+, Na+, Cl- and O-2.
Har ion ki valency us k symbol k upper right corner pr likhi jati ha. jesa k calcium ki valency +1 ha jo k is k symbol (Ca) k uper right corner pr likhi jy gi Ca+. or isi trha age negative ion ko dekhen to oxygen ki valency -2 ha to isy b O k uper right corner pr likhen ge O-2.
3. The valencies of each ion is brought to lower right corner by 'cross-exchange' method. e.g,
Chemical formula likhte huay ions ki valency ko un k symbol k niche right corner pr cross-exchange method k zreay shift kiya jata ha. jesa k uper example me btaya gya ha k NaCl me sodium ka positive ion chlorine k neche right corner pr or chlorine ka negative ion sodium k neche right corner pr cross-exchange method k zreay shift kiay gy hn. isi trha CaCl2 or CaO k ions ki valency ko b isi method k zreay shift kiya gya ha.
4. If the valency of both the ions are same then it is not written in the formula but if they are different then they will written at the positions which are described above.
Agr compound me majood dono ions ki valency same ho to un ki valency chemical formula likhte huay ni likhi jati. Jin ions ki valency different ho unhi ko cross-exchange method k zreay likha jata ha. jesa k uper example me b btaya gya ha k NaCl k dono ions ki valency 1 ha to is k chemical formula me 1 ko ni likha gya lakin CaCl2 me calcium ion pr +2 or chlorine k ion pr -1 charge ha, is liay cross-exchange method k zreay ions k valency in k nechy ki trf shift kr di gi ha.
5. If there is a radical in the compound instead of ion, which carry a net charge on it, it will also written as explained in the above points. For Example:- in Al2(SO4)3 , SO4 is a radical which has a net charge of -2 and the aluminum ion carry +3 charge, so both the valencies are shifted by cross-exchange method.
Agr compound k chemical formula me ion ki jga radical majood ho, jis pr net charge likha jata ha to use b same isy process k zreay likha jata ha jo k uper k points me smjaya gya ha. For Example:- Al2(SO4)3 , me SO4 ek radical ha jis ks net charge -2 ha or is k sath wale aluminium k ion pr +3 ka charge ha, jinhe cross-exchange method k zreay shift kr diya gya ha. jesa k uper wale points me smjaya ja chuka ha.
Written By:- M.Ashir Azeem
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