magnesium sulfide MgS calcium sulfide CaS ionic bondng Lewis 2D dot & cross electronic diagrams 3D ball & stick close packed space filling models crystal lattice melting point ionic bond compound magnesium sulphide calcium sulphide Doc Brown's chemistry revision notes

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2f. The ionic bonding of the compounds magnesium sulfide MgS and calcium sulfide CaS

[Author © Dr Phil Brown PhD: Doc Brown's chemistry exam revision notes on the ionic bonds of magnesium sulfide & calcium sulfide, suitable for students of UK GCSE Science level AQA, Edexcel, OCR, WJEC and CCEA GCSE chemistry courses, ~US grades 9-10 chemistry, also useful for more advanced pre-university A level chemistry courses [ionic bonding page updated April 11th 2026 *]

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Part 2 Ionic Bonding: compounds and properties

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Example 2f. A Group 2 Alkaline Earth Metal combining with a Group 6 non–metallic element

* 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

The ionic compounds MAGNESIUM SULFIDE and CALCIUM SULFIDE
Where the elements magnesium, calcium and sulfur are in the Periodic Table

Magnesium oxide MgO, magnesium sulfide MgS and calcium sulfide CaS will be similar electronically and give identical giant ionic lattice structures.

Group 2 metals lose the two outer electrons to give the stable 2+ positive ion (cation) and S and O, both non–metals in Group 6, have 6 outer electrons and gain 2 electrons to form 2– negative ion (anion).

For magnesium sulfide: Mg (2.8.2) + S (2.8.6) ==> Mg²⁺ (2.8) S^2– (2.8.8)

For calcium sulfide: Ca (2.8.8.2) + S (2.8.6) ==> Ca²⁺ (2.8.8) S^2– (2.8.8)

so both the magnesium/calcium and sulfide ions have a full outer shell like a noble gas

The dot and cross (ox) diagrams will be identical to that for calcium oxide above, except Mg instead of Ca (same group) and S instead of O (same group of Periodic Table). eg

The electronic dot & cross diagrams for the ionic bonding in magnesium sulfide and calcium sulfide

electronic structure of magnesium sulfide MgS

Lewis diagram for magnesium sulfide

Melting point of magnesium sulfide is 2000^oC

electronic structure of calcium sulfide CaS

Lewis diagram for calcium sulfide

Solid magnesium sulfide and calcium sulfide consist of a giant ionic lattice.

Melting point of magnesium oxide is 2525^oC

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 2 Alkaline Earth Metal combining with a Group 6 non–metallic element

Predicting formulae and names

Gp2\6 O S

Mg magnesium oxide
MgO
magnesium sulfide
MgS

Ca calcium oxide
CaO
calcium sulfide
CaS

Sr strontium oxide
SrO
strontium sulfide
SrS

Ba barium oxide
BaO
barium sulfide
BaS

All the formula highlighted in yellow can be described in the same way as magnesium oxide, magnesium sulfide, calcium oxide or calcium sulfide

The Group 2 Alkaline Earth Metal atom loses two electrons to form a doubly charged positive ion

The Group 6 non–metal atom gains two electrons to form a doubly charged negative ion

Note that these formulae are empirical formula - the simplest whole number ratio of atoms in the formulae

All of these compounds consist of a giant ionic lattice like sodium chloride.

See also 2e. Details of ionic bonding in magnesium oxide & calcium oxide (Group 2 + Group 6)

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