Introduction to Chemistry – Background for Nanoscience and Nanotechnology

1. Introduction to Chemistry – Background for Nanoscience and Nanotechnology Prof. Petr Vanysek

2. Introduction to Chemistry:Compounds

5. Chemical Bonding • Covalent bonds • Ionic bonds • Metal bonding

6. Covalent bonds • Covalent bonding is when electrons are shared between to atoms or more. • The number of covalent bonds an atom is likely to form is determined by its place in the periodic table and the number of valence electrons it has. • An atom will share electrons with another atom so that it results in them both having a full valence shell. Usually this will be 8 electrons.

7. Ionic bonds • When a metal and a non-metal form bonds they are typically ionic bonds where electrons are transferred from the metal to the non-metal. • Some metals will lose enough electrons to achieve a complete valence shell. • Non-metals will usually gain enough electrons to achieve a complete valence shell. • Many metals are able to form ions with more than one charge.

8. Metal bonding • In metals the atoms are held together by metal bonding. Electrons can easily transfer from one atom to the next. This suggests a model of positive ions in a sea of electrons. Metals can conduct electricity because electrons flow easily in any direction.

9. Covalent and Ionic Bonding

10. Polar Molecules • Polar Molecules • If the electron density is not distributed evenly around a molecule then they are polar.

11. Intermolecular BondingBonding between moleculesvan der Waals forces • Hydrogen bonding • This relatively strong type of inter-molecular bonding which typically occurs between a hydrogen atom of one molecule and an electron pair or electronegative atom of another molecule. • Multiple hydrogen bonds hold the DNA double helix together. • Dipole interaction • London forces • These are induced forces caused by a temporary rearrangement of the electron clouds when molecules bump together.

12. H O Hydrogen Bonding + + - - H

13. H H O O H H Hydrogen Bonding

14. Dipole Interaction • http://www.chemguide.co.uk/atoms/bonding/vdw.html • The partial positive and negative ends of the molecules hold the molecules together.

15. London Forces London forces are induced dipoles caused by temporary rearrangement of the electron cloud. Two hexane molecules approach. The hexane molecules bump into each other. The electron clouds rearrange to form a temporary dipole. - - - + + + - - - + + +

16. H H ( ) nCH2=CH2 C C n H H Polymers • Polymers are large chainlike molecules that are built from smaller molecules called monomers. • For example polyethylene is formed from ethylene: • Proteins are natural polymers. • http://www.pslc.ws/macrog.htm

17. Chemical Reactions • Involve the making or breaking of chemical bonds. • Chemical reactions result in making a new substance with different properties from the original substance.

18. Grains Crystal Crystals Electron orbitals Atom Unit Cell Structure of Materials

19. Tissue Cells Biological Organization Organelles Membranes Proteins Nucleic Acids

22. Review of Chemistry • States of Matter • Atoms, Molecules and Ions • Subatomic particles • Periodic Table • Covalent and ionic bonding • Chemical reactions • Intra-molecular forces • Polymers