2c. The ionic bonding of the compound sodium 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 2c. A Group 1 Alkali Metal combining with a Group 7 Halogen non–metal

* metals \ non-metals (zig-zag line)

Pd metals Part of the modern Periodic Table

Pd = period, Gp = group

metals => non–metals
Gp1 Gp2 Gp3 Gp4 Gp5 Gp6 Gp7 Gp0
1

1H  Note that H does not readily fit into any group

2He
2 3Li 4Be atomic number Chemical Symbol eg 4Be 5B 6C 7N 8O 9F 10Ne
3 11Na 12Mg 13Al 14Si 15P 16S 17Cl 18Ar
4 19K 20Ca 21Sc 22Ti 23V 24Cr 25Mn 26Fe 27Co 28Ni 29Cu 30Zn 31Ga 32Ge 33As 34Se 35Br 36Kr
5 37Rb 38Sr 39Y 40Zr 41Nb 42Mo 43Tc 44Ru 45Rh 46Pd 47Ag 48Cd 49In 50Sn 51Sb 52Te 53I 54Xe
6 55Cs 56Ba Transition Metals 81Tl 82Pb 83Bi 84Po 85At 86Rn
Ionic compound SODIUM CHLORIDE - where sodium and chlorine are in the Periodic Table

 

e.g. sodium + chlorine ==> sodium chloride NaCl or its ionic formula Na+Cl 

In terms of electron arrangement in the formation of the ionic compound sodium chloride, the sodium donates its outer electron to a chlorine atom forming a single positive sodium ion and a single negative chloride ion.

The atoms have become stable ions, because electronically via electron transfer ...

... sodium becomes like neon (sodium ion, Na+) and chlorine like argon (chloride ion, Cl).

Na (2.8.1) + Cl (2.8.7) ==> Na+ (2.8) Cl(2.8.8)

add diagrams of original atoms from 4_71atom ? group pages?

can be summarised electronically to give the stable 'noble gas' structures as [2,8,1] + [2,8,7] ==> [2,8]+ [2,8,8]

so both the sodium and chloride ions have a full outer shell like a noble gas

ONE (c) doc batom combines withONE(c) doc b atom to form (c) doc b(c) doc b

 

Note in this electron diagram, only the original outer electrons are shown above.

The outer electron of the sodium atom (2.8.1) is 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 sodium ion also attains a stable noble gas electron structure (2.8).

The valencies of Na and Cl are both 1, that is, the numerical charge on the ions. sodium fluoride NaF, potassium bromide KBr and lithium iodide LiI etc. will all be electronically similar.

Only the outer valency electrons of the chloride ion are shown, the 'blob' electron represents the electron from the sodium atom which is accepted by the chlorine atom to form the chloride ion.

The charge on the sodium ion Na+ is +1 units (by convention shown as just +) because there is one more positive proton than there are negative electrons in the sodium ion (11p, 10e).

The charge on the chloride ion Cl is –1 units (by convention shown as just ) because there is one more negative electron than there are positive protons in the chloride ion (17p, 18e).

Note:

would represent the full electronic structure diagram of the sodium ion [2.8] and the chloride ion [2.8.8], hence the full electronic structure of sodium chloride. Note that the 'blob' and 'x' electrons are identical, but their use is just a useful visual device to show how the ions are formed. The blue circle represents the nucleus.

explain charge on ion wrt diagram 17 p, 18 surrounding e's

Above is the electronic dot & cross diagram for the ionic bonding in the ionic compound sodium chloride,

is the Lewis diagram for the formation of sodium chloride from its elements. simplified

Limitations of these dot and cross diagrams:

Although these electron arrangement diagrams show how the ionic bond is formed and the electronic structure and electrical charge on the ions, they do not give any idea on the relative size of the ions or the 3D spatial arrangement of the ions in the crystal lattice.

See comparison table

(c) doc b

Melting point of sodium chloride is 801oC


Pd metals Part of the modern Periodic Table

Pd = period, Gp = group

metals => non–metals
Gp1 Gp2 Gp3 Gp4 Gp5 Gp6 Gp7 Gp0
1

1H  Note that H does not readily fit into any group

2He
2 3Li 4Be atomic number Chemical Symbol eg 4Be 5B 6C 7N 8O 9F 10Ne
3 11Na 12Mg 13Al 14Si 15P 16S 17Cl 18Ar
4 19K 20Ca 21Sc 22Ti 23V 24Cr 25Mn 26Fe 27Co 28Ni 29Cu 30Zn 31Ga 32Ge 33As 34Se 35Br 36Kr
5 37Rb 38Sr 39Y 40Zr 41Nb 42Mo 43Tc 44Ru 45Rh 46Pd 47Ag 48Cd 49In 50Sn 51Sb 52Te 53I 54Xe
6 55Cs 56Ba Transition Metals 81Tl 82Pb 83Bi 84Po 85At 86Rn
A Group 1 Alkali Metal combining with a Group 7 Halogen non–metal
 

Li is 2.1, K is 2.8.8.1, F is 2.7, rest of dot and cross diagram is up to you.

Gp1\7 F Cl Br I
Li LiF LiCl LiBr LiI
Na NaF NaCl NaBr NaI
K KF KCl KBr KI
Rb Rb RbCl RbBr RbI
Cs CsF CsCl CsBr CsI

All the formula highlighted in yellow can be described in the same way as sodium chloride

The Group 1 Alkali Metal atom loses one electron to form a singly charged positive ion

The Group 7 Halogen atom gains one electron to form a singly charged negative ion

empirical formula - mention on each page and explain

 


What next?

Recommend next: ?

 

Sub-index for: Part 2 Ionic Bonding: compounds and properties

 

Index for ALL chemical bonding and structure notes

 

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