Soild state lecture 1
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This document discusses atomic structure and interatomic bonding. It begins by explaining why atomic structure is important for understanding materials' properties. It then lists the learning objectives, which are to describe two atomic models, quantum energy levels, and different types of bonds. The rest of the document defines key atomic concepts like atomic number and mass, electrons and their quantum numbers, electron configurations, and the periodic table. It aims to provide foundational knowledge about atomic structure and how this relates to bonding between atoms.
Soild state lecture 1
- 1. Chapter I Atomic structure and interatomic bonding
- 2. Why study atomic structure and inter atomic bonding? Because the type of bond allows us to explain the material’s properties For example carbon which may exist as both graphite and diamond .
- 3. Learning objectives 1- name the two atomic models cited and note the differences between them. 2- describe quantum-mechanical principle that relates to electron energies. 3- plot attractive repulsive and net energies versus interatomic separation for two atoms or ions . 4- describe ionic , covalent , metallic , hydrogen and Vander Waals bonds
- 4. Atomic structure Fundamental concepts:- The atom consist of :- Nucleus electrons
- 5. Atomic number (Z):- the number of protons in the nucleus . Note: atomic number equals the number of electron s for electrically neutral or complete atoms . The atomic mass (A) :- the sum of the masses of protons and neutrons with in nucleus .
- 6. Isotopes :- atoms of some elements have two or more different atomic masses . The atomic weight:- the weighted average of the atomic masses of the atom’s naturally occurring isotopes .
- 7. Units : Atomic mass : amu Atomic weight: amu per atom (molecules) 1 amuatom = 1 gmol
- 8. Electrons in atoms Atomic model Bohr model:- 1- electrons are assumed to revolve around the atomic nucleus in discrete orbitals ( position of particular electron ). 2- stipulates that the energies of electrons are quantized that electrons are permitted to have only specific values of energy .
- 9. 3- an electron may be change energy but in doing it must make quantum jump to higher energy (with absorption of energy ) or to lower energy (with emission of energy ).
- 10. Wave mechanical model 1- electron is considered to exhibit both wave like and particle like characteristics . 2- an electron is no longer treated as particle moving in a discrete orbital but rather position is considered to be the probability of electron’s being at various locations around the nucleus .
- 11. Quantum numbers Every electron in an atom is characterized y four parameters called quantum number. The size, shape , and spatial orientation of an electron’s probability density can explain by these number. 1- principle quantum number (N):- N = K , L , M , ……. 2- angular quantum number (L) :- L = N-1 3- magnetic quantum number (Ml):- Ml = +,- L 4- Spin quantum number (Ms):- It has two values possible (+12 ,-12)
- 12. Electron configurations To determine the manner in which these states are filled with electrons we use pauli exclusion principle (each electron state can hold no more than two electrons which must have opposite spins ). So find S is filled by 2 electrons . P filled by 6 electrons -d is filled by 10 electrons F is filled by 14 electrons
- 13. Not all possible states in atoms are filled with electrons and most atoms the electron fill up the lowest possible energy states in the electron shell and sub shell .
- 14. Valance electrons Electrons that occupy the outmost filled shell. These electron are extremely important because it used in the bonding between atoms to form atomic and molecular aggregates Further more many of the physical and chemical properties of solids are based on these valance electrons
- 15. Stable electron configuration The states with in the outermost or valance electron shell are completely filled . Ex :- (Ne , Ar , Kr, He ) inert gasses Some atoms of the elements that have unfilled valance shell assume stable electron configuration by gaining or losing electrons to form charged ions or by sharing electrons with other atoms . under special circumstance , the S and P orbital combine to form hybrid SP n orbital N (1,2,3)
- 16. The 3A ,4A, and 5A group elements of periodic table are those which most often form these hybrids. The driving force for the formation of hybrid orbitals is lower energy state for the valance electrons.
- 17. The periodic table All the elements have been classified according to electron configuration in periodic table. Elements are situated with increasing atomic number in seven horizontal rows called periods. The arrangement is such that all arrayed in a given column or group have similar valance electron structures as well as chemical and physical properties . These properties change gradually moving horizontally a cross each period .
- 18. Electropositive :- Elements are capable of giving up their few valance electrons to become positively charged ions. Electronegative:- Elements accept electrons to form negatively charged ions or they share electrons with other atoms .
- 19. Electro negativity increases in moving from left to right and bottom to top .