BONDING IN MINERALS

1. BONDING IN MINERALS
GUIDED BY
Dr. Narendra Joshi
Ms. Tanishka Soni
PRESENTED BY
Khushbu Yadav
CLASS - M.Sc. (I Sem.)
Govt. Holkar Science College , Indore (M.P)

2. CONTENT :
• Introduction
• Types of bonding ;
1. Ionic bonding
2. Covalent bonding
3. Metallic bonding
4. Residual bonding
 Van der waals bonding
 Hydrogen bonding
• Role in crystal chemistry.
• Applied aspect in geology.
• Conclusion.
• Reference.

3. INTRODUCTION :
What is bonding forces ?
o Forces of attraction and repulsion which act between Atom ,
Molecules , Ions.
o Attraction – forces which keeps the atoms together.
o Repulsion - when opposite charged particles encounter each
other.
o Such forces also act in case of Liquid or single molecule.

4. Bonding in minerals ?
o The force that determine the arrangement of atoms , ions in
minerals.
o The force that binds together the ions within crystal .
o This force is responsible for their Physical and Chemical
properties . Like -
Hardness,
Cleavage,
Electrical and Thermal conductivity,
Compressibility .

5. • Types of bonding
1. Ionic bonding
2. Covalent bonding
3. Metallic bonding
fig no. 1, source: net
4. Residual bonding ; Van der wall bonding
Hydrogen bonding

6. 1. Ionic bonding
o Ionic bonding ; when negatively(electrons)and
positively(protons) charged particles attract each other.
oPositively charged cations attract negatively charged
anions producing ionic bond in minerals.
o An ionic bond is achieved when one or more electrons
transferred to the valence shell of one another.
o Atoms strong tendency to achieve inert gas configuration.

7. o Ionic bonds are most important for bonding between
oxygen and Mg, Si, Al, Na, K.
o Primary bonding type in silicate and oxide minerals.
o Ionic bonds are non – directional in nature, that is the
attractive forces occur from all Direction.
o Properties of minerals with Ionic Bonds are -
 Dissolve easily in polar solvent.
 Tend to form crystals with high symmetry.

8. Fig no. 2 , source : britiannica.com

9.  Moderate hardness and specific gravity.
 Fairly high melting points.
 Poor conductors of Electricity and Heat.
 NOTE : Lack of electrical conductivity in ionic bonding of
crystals is due to stability of ions (neither gain nor loose
electrons).

10. o For example : Na has one electron in its outermost shell. It will
tend to give up this electron to become Na+1 ion.
o Similarly, Cl has 7 electrons in its outermost shell and would
like to gain electron to become Cl-1
oForce of attraction between these oppositely charged ion result
in an Ionic bond.
oThe strength of the bond is, as measured by Melting point , is
inversely proportional to its Bond length.

11. Fig. no. 3 , Sources : geoscience.com

12. 2.Covalent bond :
o The electron sharing or covalent bond is the strongest
chemical bond.
o Atoms held together by " sharing electrons", i.e a electron do
"double – duty".
o As a result of sharing of electrons, two atoms show bonding.
o The number of covalent bond can be predict by counting the
electrons required to achieve stable electronic configuration.

13. o Covalent bonds are very strong directional bonds, that is they
occur along the zone of electron are shared.
o Covalently bonded crystals have the following properties :
 Relatively insoluble in polar solvent .
 High melting temperatures.
 Generally form crystals structures of low symmetry.
 High hardness.

14. RESULTS IN
COMPOUND
LIKE DIAMOND ,
GRAPHITE
STRONG BOND.
Fig no. 4 , source : sciencealert

15.  Generally poor conductors of heat and electricity.
 Formed between atoms of similar electron negativity.
 Great stability.
 NOTE : In reality, bonding between atoms not purely covalent
or ionic but rather as a mixture of bonds.
Amount of each type is determined by electron negativity.

16. Examples :
 Elements near the middle of the periodic table such as C, Si , Al,
S have tendency to form 4 covalent bonds.
These are multiple shared pairs of electron between two atomic .
centers.
Result in very stable groups.
 Carbon is good example . It has 4 electrons in its outer shell and
needs 4 more to achieve stable electronic configuration.
It can share 4e with other carbon atoms to form covalent bond.

17. Fig. no. 5 Source : sciencealert

18. 3. Metallic bond
o The attractive force with the nuclei with their filled electron
orbits but not valence electron called metallic bond.
o Each atom sharing electrons freely in their orbit .
o The atomic nuclei plus non valence electron bound together
by aggregate electrical charge of a cloud.
o Some of electrons freely move unlike other bonds.
o Pure metals appear to bind in this way.

19. Fig. no. 6 , Source: sciencealert

20. o Crystals are formed with metallic bonds have following
properties :
 Low to moderate hardness
 Usually very malleable and ductile.
 Good thermal and electrical conductors.
 Soluble in acids only.
 Crystals with high degree of symmetry.

21. EXAMPLES : COPPER AND GOLD .
Photo no. 1 Source: Wikipedia Photo no. 2 Source : Wikipedia

22. Photo no. 3 , Source : Wikipedia

23. 4. Residual bonding
o Residual bonds are weak bonds .
o Involve partially charged atoms or molecules.
o This partial charges are created when electrons concentrated on
one side of atoms or molecules.
o Sometimes creates a polar atom which has concentration of
negative charges on one side and positive on other.

24. oWhen residual bonds occur in crystal structure , generally
form planes or zones of easy cleavage .
oTwo special cases are :
• Van der waals bonds
• Hydrogen bonds

25.  Van der waals bond
oThe weak bond , ties neutral molecules and essentially
uncharged units by residual charge on their surface.
o Weakest of the chemical bonds.
o Weak dipole attraction is induced between two atoms.
oThis induce similar effect in neighbor molecules structure that
bounded by weak dipole effect.
oEspecially effective over large distances in molecular structures.

26. o Common in organic compounds and solidified gas.
o Not often encounter in minerals .
o Generally defines zone of cleavages or low hardness.
o Low symmetry.
o Low melting point and insulator in both solid and liquid state.
o Crystal soft and somewhat plastic.

27. Examples :
 Most common form is sulfur made of discrete S8 molecules
with cyclic structures
Within the ring covalent bonding, but adjacent ring held
together by Van der waals bonds.
Result in low hardness ( H = 1 or 2)and melting point (112.8).
 Also mineral graphite , consist of covalent bonded sheets of
carbon and linked by van der waal force.

28. Fig no. 6 Sources : sciencealert Fig. no. 7 , Sources : sciencealert

29.  Hydrogen bond
o An electrostatic bond between positively charged H ions and
negatively charged ions such as O2-or N3-.
oPolar molecules can form crystalline structures by attraction
between oppositely charged end.
oHydrogen has only one electron , when it gives that e-
remaining proton of H nucleus unshielded.
oThis positive ion has ability to form hydrogen bond.

30. Fig no. 8 , Source : sciencealert

31. o The closeness of approach form dipole – dipole bond .
oThis dipole – dipole bond is weaker than covalent , ionic and
metallic bonding.
oThis bond is considerably stronger than vander waals bond.
oSimilarly, an OH-1 common in sheets minerals like micas &
clay minerals.
oLayers of OH-1 molecules in sheet silicates result in easy
cleavage along the planes.

32. fig no. 9 , Sources : sciencealert

33. • ROLE IN CRYSTAL CHEMISTERY
ü BONDS TELL THE CRYSTAL STRUCTURE AND PACKING .
ü CHEMICAL BONDING HAS GREAT ROLE IN
DETERMINING CRYSTAL FORM.
ü THREE WAYS IN WHICH IONS OF MOST METALS OR PACKED
TOGETHER :- CUBIC CLOSE PACKING.
BODY CENTRED PACKING.
HEXAGONAL CLOSE PACKING.

34. • Applied aspect in mineralogy
Chemical bonding is used in mineral identification.
 Bonds determine the physical as well as chemical
composition of minerals.
 Physical properties like hardness , cleavages , habit
,tenacity etc.
 Bonds also control crystalizations of minerals by their inter-
moleculer arrangement.

35. • Conclusion :
 Bonds are binding forces in mineral crystals , responsible for
their interatomic structure.
There is more than one type of bonding in minerals , only one
type of bonding is rare.
 Like graphite , silicates of mica and clay
minerals, amphiboles,pyroxenes have more than single
bonding.

36. • References :-
 BOOKS -
 Mineral Sciences , Cornelis klein(22nd Edition) .
 Mineralogy, Dexter Perkins (3rd Edition).
 Textbook of mineralogy , Rutley (27th edition)
 WEBSITE -
 www.britainnica.com
 www.geosciencess.fau.edu
 www.sciencealert.com