2d. The ionic bonding of the compounds magnesium chloride and calcium chloride
Doc Brown's Chemistry: Chemical Bonding and structure GCSE level, IGCSE, O, IB, AS, A level US grade 9-12 level Revision Notes
Example 2d. A Group 2 Alkaline Earth Metal combining with a Group 7 Halogen non–metal
* metals \ non-metals (zig-zag line)
e.g. magnesium + chlorine ==> magnesium chloride MgCl2 or ionic formula Mg2+(Cl–)2
In terms of electron arrangement in the formation of the ionic compound magnesium chloride, the magnesium donates its two outer electrons to two chlorine atoms forming a double positive magnesium ion and two single negative chloride ions via electron transfer.
Mg (2.8.2) + 2Cl (2.8.7) ==> Mg2+ (2.8) 2Cl– (2.8.8)
can be summarised electronically as [2,8,2] + 2[2,8,7] ==> [2,8]2+ [2,8,8]–2 via electron transfer
so both the magnesium and chloride ions have a full outer shell of electrons like a noble gas
ONE atom combines withTWO atoms to form
Note in this electron diagram, only the original outer electrons are shown above.
The outer electrons of the magnesium atoms (2.8.2) are transferred to the outer shell of the chlorine atom (2.8.7) giving it a complete octet shell of outer electrons, just like a noble gas (2.8.8). At the same time, the magnesium ion also attains a stable noble gas electron structure (2.8).
The two outer electrons of the calcium atoms (184.108.40.206) are transferred to the outer shell of two chlorine atoms (2.8.7) until it has a complete octet shell of outer electrons, just like a noble gas (2.8.8). At the same time, the calcium ion also attains a stable noble gas electron structure (2.8.8). The blue circle represents the nucleus.
is the Lewis diagram for the formation of calcium chloride
Melting point of calcium chloride is 772oC
All the formula highlighted in yellow can be described in the same way as magnesium chloride or calcium chloride
The Group 2 Alkaline Earth Metal atom loses two electrons to form a doubly charged positive ion
The Group 7 Halogen atom gains one electron to form a singly charged negative ion
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