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Atomic Structure        ….a brief overview…..
Important Highlights•   INTRODUCTION•   RUTHERFORD’S ATOMIC MODEL•   BOHR’S ATOMIC MODEL•   DISTRIBUTION OF EXTRA-NUCLEAR ...
Introduction• ATOM : An atom is the smallest particle of an element, which    Can not be subdivided.    Does not exist i...
Rutherford’s Atomic Model• Also known as “Planetary Model” of Atom.K e y F e a tu re s :• An atom consists of a central nu...
Drawbacks of Rutherford’s Model•    It could not explain the stability of the atom. A/c to    classical theory of mechanic...
RU  TH     ER       FO                                                                    E   L            RD             ...
Bohr’s Atomic ModelThe main points of Bohr’s atomic model are….• Electrons revolve around the nucleus in orbits that have ...
Bohr postulated that the angular momentum of the electron is  quantized as shown…Where, h=6.626*10^(-34) JsThen by using s...
Deduced Formulae:• Radius, r= (n^2/Z)*0.529 Å• Energy, E= -(Z^2/n^2)* 13.6 eV• Wave No.=1/wave-length=R(1/nf2-1/ni2)• Velo...
e.g. Emission of a Quantum:1st Balmer Transition                    -3.4eV                  BESU SHIBPUR,HOWRAH
Limitation of Bohr’s Atomic Model• The Bohr atomic model is applicable only for one-electron  system. e.g. H, He+, Li++, B...
Concept of shells and subshells• Shells, n, represents the distance of an electron from  Nucleus. It is represented by K,L...
Quantum Numbers of Wave funtionsQuantum #   Symbol     Values              DescriptionPrincipal   n          1,2,3,4,…    ...
Electronic ConfigurationThe electrons gather around the nucleus in quantum orbitals  following four basic rules, called th...
Electronic Configuration contd.Hence, Aufbau Principle  Gives order of filling of electrons in  different subshells. It c...
Electronic Configuration contd.• The electronic configuration of elements generally follows  Aufbau principle.• except som...
Wave Nature of an Atom• Wave–particle duality postulates that, all particles exhibits  both particle as well as wave chara...
Atomic Number• Atomic Number, Z: The number of protons in an atom.• As atoms are neutral,So,    N(p)=N(e)=ZWhere, N(p)= n...
Mass NumberMass Number: The total numbers of neutrons andprotons in an atom.So, if we know mass no. and atomic number, we ...
Notation of an Atom  Mass Number                     65                       Cu                     29   Atomic Number   ...
References…...• http://www.answers.com/topic/electron-configuration• http://www.sparknotes.com/chemistry/fundamentals/atom...
Thanking You…!Presented By……… Navin Kumar COMPUTER SCIENCE & TECHNOLOGY BENGAL ENGINEERING & SCIENCE UNIVERSITY SHIBPUR, H...
….question please….!!         BESU SHIBPUR,HOWRAH
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Atomic structure

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Transcript of "Atomic structure"

  1. 1. Atomic Structure ….a brief overview…..
  2. 2. Important Highlights• INTRODUCTION• RUTHERFORD’S ATOMIC MODEL• BOHR’S ATOMIC MODEL• DISTRIBUTION OF EXTRA-NUCLEAR ELECTRONS IN SHELLS & SUB-SHELLS• ELECTRONIC CONFIGURATION OF ATOM• WAVE-NATURE OF AN ATOM• ATOMIC NUMBER• MASS NUMBER BESU SHIBPUR,HOWRAH
  3. 3. Introduction• ATOM : An atom is the smallest particle of an element, which  Can not be subdivided.  Does not exist in free state. But,  Participate in chemical reaction.The structure of an atom can be broadly divided into two parts  Nuclear Parts  Extra-Nuclear Parts Nuclear part basically consist of 2 major particles– protons & neutrons. Apart from this there are some more tiny particles such as deuteron, neutrino, positron etc. Extra-Nuclear parts consists of mainly electrons. BESU SHIBPUR,HOWRAH
  4. 4. Rutherford’s Atomic Model• Also known as “Planetary Model” of Atom.K e y F e a tu re s :• An atom consists of a central nucleus.  This nucleus is composed of positively charged protons, and electrically uncharged (neutral) neutrons.• Negatively charged electrons revolve around the nucleus in definite orbits.• The orbits themselves can be at any distance from the nucleus.• In any atom, the number of protons is equal to the number of electrons, and hence it is electrically neutral. BESU SHIBPUR,HOWRAH
  5. 5. Drawbacks of Rutherford’s Model• It could not explain the stability of the atom. A/c to classical theory of mechanics, during uniform revolution, any body accelerates, & an accelerating charged particle must emit radiation, and lose energy. Due to the fact, the electron must emit radiation and lose energy. As a result, the electron will follow a spiral path, and ultimately fall into nucleus .So, Rutherford has given concept of unstable atom.• The Rutherford’s model of atom does not say anything about the arrangement of electrons in an atom. BESU SHIBPUR,HOWRAH
  6. 6. RU TH ER FO E L RD ’S MOD AT C OM O MI IC MO S AT ’ DE HR L BO BESU SHIBPUR,HOWRAH
  7. 7. Bohr’s Atomic ModelThe main points of Bohr’s atomic model are….• Electrons revolve around the nucleus in orbits that have fixed radius and energy. So, such orbits are also known as stationary orbit ,Energy shells etc.• The energy of the orbit is related to its size. The lowest energy is found in the smallest orbit and its vice-versa.• Radiation is absorbed or emitted when an electron jumps from one orbit to another. BESU SHIBPUR,HOWRAH
  8. 8. Bohr postulated that the angular momentum of the electron is quantized as shown…Where, h=6.626*10^(-34) JsThen by using simple physical equation he deduced the expression for energy,velocity,radius,wavelength,wave-no. etc. L=nh/2ᴨ= mvr F= Ze*e/r*r=mv*v/r Where,L=Angular accn., Z=Atomic number, v=Orbital velocity m=mass of electron, n=Principal Quantum Number r=Radius of Orbit, h=Planck’s constant=6.626*10^34Js BESU SHIBPUR,HOWRAH
  9. 9. Deduced Formulae:• Radius, r= (n^2/Z)*0.529 Å• Energy, E= -(Z^2/n^2)* 13.6 eV• Wave No.=1/wave-length=R(1/nf2-1/ni2)• Velocity, v=(Z/n)*21.88*10^5 m/s BESU SHIBPUR,HOWRAH
  10. 10. e.g. Emission of a Quantum:1st Balmer Transition -3.4eV BESU SHIBPUR,HOWRAH
  11. 11. Limitation of Bohr’s Atomic Model• The Bohr atomic model is applicable only for one-electron system. e.g. H, He+, Li++, Be+++ etc.• The Bohr Model provides an incorrect value for the ground state orbital angular momentum.• It does not predict the relative intensities of spectral lines.• The Bohr Model does not explain fine structure and hyperfine structure in spectral lines.• It violates the Heisenberg Uncertainty Principle because it considers electrons to have both a known radius and orbit.• It does not explain the Stark’s & Zeeman’s Effect. BESU SHIBPUR,HOWRAH
  12. 12. Concept of shells and subshells• Shells, n, represents the distance of an electron from Nucleus. It is represented by K,L,M,N,O,…for n=1,2,3,4,..• Shell no., n, also represents the maximum no. of electrons accommodated by a particular shell, which is 2n(2). i.e. for n=1, First Shell, maximum no. of electrons=2. Similarly, for n=2, it’s 8. n=3, it’s 18 and so on.• Subshell represents the traversal path of any electron in 3D view or, shape of the Orbital. For any Orbit ,n, it’s value ranges from 0 to(n-1). It is represented by s,p,d,f,… for l=0,1,2,3,… BESU SHIBPUR,HOWRAH
  13. 13. Quantum Numbers of Wave funtionsQuantum # Symbol Values DescriptionPrincipal n 1,2,3,4,… Size & Energy of orbitalAngular l 0,1,2,…(n-1) Shape of orbitalMomentum for each nMagnetic ml -l…,0,…+l Relative orientation of orbitals within for each l same lSpin ms +1/2 or –1/2 Spin up or Spin down Angular Momentum Quantum # l Name of Orbital 0 s (sharp) 1 p (principal) 2 d (diffuse) 3 f (fundamental) 4 g BESU SHIBPUR,HOWRAH
  14. 14. Electronic ConfigurationThe electrons gather around the nucleus in quantum orbitals following four basic rules, called the Aufbau principle.• no two electrons in the atom will share the same four quantum numbers n, l, m, and s. (Pauli’s Exclusion Principle)• electrons will first occupy orbitals of the lowest energy level.• orbitals will be filled with the same spin number until all the orbitals are filled, before it will begin to fill in the opposite spin. (Hund’s Rule of maximum multiplicity)• (n+l) Rule: electrons will fill orbitals by the sum of the quantum numbers n and l. In case equal values of (n+l), orbitals with the lower value of n, will be filled first. BESU SHIBPUR,HOWRAH
  15. 15. Electronic Configuration contd.Hence, Aufbau Principle  Gives order of filling of electrons in different subshells. It can be shown as follows….• 1s2• 2s22p6• 3s23p63d10• 4s24p64d104f14• 5s25p65d105f14(5g18)• 6s26p66d106f14(6g18)(6h22)• 7s27p67d106f14(6g18)(6h22)(7i26) BESU SHIBPUR,HOWRAH
  16. 16. Electronic Configuration contd.• The electronic configuration of elements generally follows Aufbau principle.• except some cases viz. Cu,Cr type d-block elements(due to some stability factor). BESU SHIBPUR,HOWRAH
  17. 17. Wave Nature of an Atom• Wave–particle duality postulates that, all particles exhibits both particle as well as wave characteristics.• Louis-Victor de Broglie describes the atom considering "Dual Properties of Matter”.• He formulated a hypothesis, claiming that all matter, not just light, has a wave-like nature; he related wavelength (denoted as λ), and momentum (denoted as p): λ =h/pThis is the generalization of Einstein’s and Planck’s Equation. BESU SHIBPUR,HOWRAH
  18. 18. Atomic Number• Atomic Number, Z: The number of protons in an atom.• As atoms are neutral,So, N(p)=N(e)=ZWhere, N(p)= number of protons N(e)=number of electrons Z=Atomic Number. BESU SHIBPUR,HOWRAH
  19. 19. Mass NumberMass Number: The total numbers of neutrons andprotons in an atom.So, if we know mass no. and atomic number, we canfind out the number of neutrons in an atom .Mass Number - Atomic Number=Number of neutrons BESU SHIBPUR,HOWRAH
  20. 20. Notation of an Atom Mass Number 65 Cu 29 Atomic Number BESU SHIBPUR,HOWRAH
  21. 21. References…...• http://www.answers.com/topic/electron-configuration• http://www.sparknotes.com/chemistry/fundamentals/atomicstr BESU SHIBPUR,HOWRAH
  22. 22. Thanking You…!Presented By……… Navin Kumar COMPUTER SCIENCE & TECHNOLOGY BENGAL ENGINEERING & SCIENCE UNIVERSITY SHIBPUR, HOWRAH BESU SHIBPUR,HOWRAH
  23. 23. ….question please….!! BESU SHIBPUR,HOWRAH
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