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    How do you draw the dot and cross diagrams/ lewis structures for polyatomic ions like a carbonate ion and a ammonium ion and a nitrate ion, and how would you know where the dative coordinate bonds are and which element has lost or gained an electron? Thank you
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    (Original post by Laraib Chaudhry)
    How do you draw the dot and cross diagrams/ lewis structures for polyatomic ions like a carbonate ion and a ammonium ion and a nitrate ion, and how would you know where the dative coordinate bonds are and which element has lost or gained an electron? Thank you
    I've never done this before but I'm pretty sure I know how to work it out from thinking about what group the atoms are in,their lone pairs and types of bonds etc.

    Ammonium ion :
    The ammonium ion is based off of ammonia which has the chemical formula NH3. Nitrogen is the central atom to the compound and it has 5 electrons in its outter shell. Therefore 3 electrons will be used to form covalent bonds with the 3 H atoms and 2 electrons will be left over to form a lone pair. The presence of a lone pair means a dative bond can form. A hydrogen ion (H+) forms a dative bond with this lone pair which adds a + to the charge of the ion as H+ ions are simply protons and protons have a positive charge. Hence NH4+

    Carbonate ion :
    Carbon is the central atom of this ion. Carbon can form 4 covalent bonds due to having 4 electrons in its outter shell so as it is bonded to 3 oxygen atoms and has a charge of 2- we can assume one oxygen is bonded via a double covalent bond and two of the oxygens are bonded with single bonds. This is because when oxygen and carbon bond a double covalent bond always forms , therefore having a single covalent bond between an oxygen and carbon atom results in a 1- charge on the oxyen. So fromm the 2- charge I know there are 2 carbon oxygen single bonds and 1 carbon oxygen double bond. This makes sense as 1 double bond and 2 single bonds require 4 electrons from the carbon and carbon has 4 electrons in its outter shell.

    Nitrate ion :
    Nitrogen is the central atom and has 5 electrons in its outter shell. As it has a 1- charge we can assume there is one nitrogen oxygen single bond and 2 nitrogen oxygen double bonds. This makes sense as 2 double bonds and 1 single bond require 5 electrons from the nitrogen and nitrogen has 5 electrons in its outter shell.

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