![• Metals possess high thermal and electrical conductivities. This
is because of the free electron movement in the lattice.
Metals exhibit ductility.
• They are brittle below a certain temperature. Metals exhibit
brittle to ductile fracture transition at a certain temperature.
Many metals like tungsten are tough. But some metal like
pure silver, aluminium, gold are soft and malleable. Their
melting points vary from 64 0 C (Potassium) to 2000 0 C
[Titanium (1812 0 C), Molydenum, Tungsten].
• Metallic alloys are extremely useful for all engineering
applications. Their high conducting values (gold, platinum,
silver, copper etc.,) make them useful as electrodes in
scientific and technical devices. Metals are opaque to light
and they reflect light energy very efficiently.
CHA. Metallic compounds](https://image.slidesharecdn.com/bondsinsolids-230313165005-33a2a34f/85/Bonds-in-solids-pptx-22-320.jpg)
Bonds in solids.pptx
- 2. • In nature one comes across several types of solids. • Many solids are aggregates of atoms. • The arrangement of atoms in any solid material is determined by the character, strength and directionality of the chemical binding forces, cohesive forces or chemical bonds. We call these binding forces as atomic interaction forces.
- 3. • The atoms, molecules or ions in a solid state are more closely packed than in the gaseous and liquid states and are held together by strong mutual forces of attraction and repulsion. • One can describe the atomic arrangement in elements and compounds on the basis of this. • The type of bond that appears between atoms in crystal is determined by the electronic structure of interacting atoms.
- 7. Ionic Bond • Ionic bond is formed when the atoms with small number of electrons on the outer shells, have a tendency to give up electrons to the atoms with an almost filled outer shell. • Ionic bond is the simplest type of interatomic bond. • By loosing electrons, metallic atoms like alkali-metals, alkaline-earth metals etc., • Ionic bonding occurs between electropositive elements (metals, i.e., those elements on the left side of the periodic table) and the electronegative elements (non- metals; i.e. on the right hand of the periodic table).
- 8. Ionic Bonds
- 9. Ionic Bond
- 10. IONIC BOND
- 11. CHA.IONIC SOLIDS • Ionic solids are generally rigid and crystalline in nature. • In ionic bonding, a metallic element loses from the outer electron shell of its atom a number of electrons equal to its valency (numerical). Obviously, an electrostatic attraction between positive and negative ions occurs. • In ionic crystal each positive ion attracts all neighbouring negative ions and vice versa, the bond itself is non- directional. • Ionic solids are generally non-conductors of electricity. • Ionic solids are highly soluble in water but insoluble in organic solvents.
- 12. COVALENT BOND • In covalent bonding, stable electron setups are expected by the sharing of electrons between neighbouring atoms. • Two neighbouring atoms each having incomplete outermost shells. • Unlike ionic bonding, the atoms participating in the covalent bond have such electronic configurations that they cannot complete their octets by the actual transfer of electrons from one atom to the other. • Obviously, there is no charge associated with any atom of the crystal. • The majority of solids incorporating covalent bonds are also bound by either ionic or Vander Waals bonds.
- 13. covalent bond • A covalent bond is formed between similar or dissimilar atoms each having a deficiency of an equal number of electrons. • When two atoms, each having a deficiency of one electron, come so close that their electronic shells start overlapping, the original atomic charge distributions of atoms are distorted and each atom transfers its unpaired electron to the common space between the atoms. • Obviously, the common space contains a pair of electrons which belongs equally to both the atoms and serves to complete the outermost shell of each atom. This is called sharing of electrons.
- 14. covalent bond • The sharing is effective if the shared electrons have opposite spins. • In such a case the atoms attract each other and a covalent bond is formed. • As the participating atoms in the bond have the same valence state, this bond is also called the ‘valence bond’.
- 15. Covalent Bonds
- 16. CHA. Covalent COMPOUNDS • Covalent compounds are mostly gases and liquids. • They are usually electric insulators. • They are directional in nature. • They are insoluble in polar solvents like water but are soluble in non-polar solvents, e.g,, benzene, chloroform, alcohol, paraffins etc. • Covalent compounds are homopolar, i.e. the valence electrons are bound to individual or pairs of atoms and electrons cannot move freely through the material as in the case of metallic bonds. • Covalent compounds are soft, rubbery elastomers, and form a variety of structural materials usually termed as plastics. • The melting and boiling points of these compounds are low.
- 17. Metallic bond • Metallic bond is formed by the partial sharing of valence electrons by the neighbouring atoms. • It is somewhat intermediate between covalent and ionic bonding. • They are formed by the elements of all subgroups A and I-III, subgroups B. • Metallic materials have one, two, or at most, three valence electrons.
- 18. Metallic bond • With this model, these valence electrons are not bound to a specific molecule in particular and are pretty much allowed to float all through the whole metal. • They might be considered having a place with the metal overall, or framing an “ocean of electrons” or an “electron cloud.” • Metallic bonds are electropositive. • When interacting with elements of other groups, atoms in a metallic crystal can easily give off their valence electrons and change into positive ions.
- 19. Metallic bond • When interacting with one another, the valence energy zones of atoms overlap and form a common zone with unoccupied sublevels. • The valence electrons thus acquire the possibility to move freely with the zone. • Obviously, valence electrons are shared in the volume of a whole crystal. Thus the valence electrons in a metal cannot be considered lost or acquired by atoms. • They are shared by atoms in the volume of a crystal, unlike covalent crystals where sharing of electrons is limited to a single pair of atoms.
- 20. METALLIC BOND
- 21. CHA. Metallic compounds • Metallic compounds are crystalline in nature due to the symmetrical arrangements of the positive ions in a space lattice . • Metallic bonding is weaker than ionic and covalent bonding, but stronger than Vanderwaals' bonding. • Metallic bonds being weak, metals have a melting point moderate to high, i.e., the melting points of metallic crystals are lower than those of electrovalent crystals. • Metals are opaque to light, because the free electrons in a metal absorb light energy.
- 22. • Metals possess high thermal and electrical conductivities. This is because of the free electron movement in the lattice. Metals exhibit ductility. • They are brittle below a certain temperature. Metals exhibit brittle to ductile fracture transition at a certain temperature. Many metals like tungsten are tough. But some metal like pure silver, aluminium, gold are soft and malleable. Their melting points vary from 64 0 C (Potassium) to 2000 0 C [Titanium (1812 0 C), Molydenum, Tungsten]. • Metallic alloys are extremely useful for all engineering applications. Their high conducting values (gold, platinum, silver, copper etc.,) make them useful as electrodes in scientific and technical devices. Metals are opaque to light and they reflect light energy very efficiently. CHA. Metallic compounds