♦ Rutherford's model of atom and its draw backs
♦ Bohr's model of atom and its draw backs
♦ Sommerfelds elliptical model
♦ Sub Energy levels - Quantum Numbers
♦ Atomic orbitals
♦ Relative energies of the atomic orbitals
♦ Electronic configuration of elements
♦ Some Physical Quantities of Atoms
♦ 1) Ionization potential
2) Atomic radius
3) Electron affinity
♦ Some principles to write electronic configuration
Aufbau principle
Hund's rule of
Pauli's exclusion principle
Maximum multiplicity
Unit-1
Important Points:
1. Electrons, protons and neutrons are called sub-atomic particles.
2. J.J. Thomson's atomic model could not explain the atomic spectra.
3. Rutherford proposed "Planetary atomic model" based on α-ray scattering
experiments.
4. According to this model, electrons are subjected to two types of forces that is
1) The force of attraction between electrons and the nucleus
2) The centrifugal force
These two forces are equal and opposite.
5. Max Planck proposed the Quantum theory of radiation.
6. E = hν Planck's constant h = 6.625 × 10–27 erg.sec. (or) 6.625 × 10–34 J.sec.
7. Bohr proposed his atomic model based on Planck's Quantum theory.
8. Bohr model explains stationary orbits, angular momentum and radiation of energy.
9. Bohr model could not explain the atomic spectra of higher elements, Zeeman effect,
quantization of angular momentum.
10. Sommerfeld proposed the elliptical orbits and sub-stationary states.
11. Orbits are indicated by "Principal Quantum number" ie 'n', sub-stationary states are
indicated by "Azimuthal Quantum number i.e 'l', orientation of orbitals is indicated by
"magnetic Quantum number" i.e, 'm' and spinning of electrons of "Spin Quantum
number" 's'.
12. l value = (n – 1), the number of 'm' values is equal to (2l + 1) and ranges from
–l....0....+l. s is +1/2 or –1/2.
13. "The region in space where there is finite probability of finding electron" is called "atomic orbital".
14. s, p, d and f orbitals are present in the orbits. 1, 2, 3 and 4 onwards (or) K, L, M and N onwards successively.
15. Orbitals having same energy are called degenerate orbitals.
16. "Electron occupies the orbital whose (n + l) value is minimum. If (n + l) value is same, it occupies the orbital having less 'n' value" ____ Aufbau Principle.
17. "No two electrons will have all the four Quantum numbers same" ___ Pauli exclusion principle.
18. "Pairing of electrons takes place when all the degenerate orbitals are occupied by one electron each" ____ Hund's rule.
19. Atomic radius is the distance between the nucleus and outermost orbital.
Units: A° ; 1A° = 10–8 cm or 10–10m.
20. Ionization potential is "the minimum energy required to remove an electron from
outermost orbital in the gaseous state".
Units: ev (or) K.J. mol–1 (or) K.Cal.mol–1.
21. Electron affinity is "the energy released when an electron is added to a neutral gaseous atom in the ground state".
Units: ev (or) K.J. mol–1 (or) K.Cal.mol–1.
Questions
SECTION - I
Short Answer Questions (2 Marks Each)
1. Explain why electrons enter into '4s' orbital but not '3d' after filling '3p' orbital?
2. Write the electronic configuration of (a) Nitrogen (b) Chromium (c) Copper?
3. Distinguish between orbit and orbital?
4. Write a short notes on Quantum theory of radiation?
5. Distinguish between Principal Quantum number and sub-level Quantum number.
SECTION - II
Very Short Answer Questions (1 Mark Each)
1. What is Planck's Quantum equation? and what is the value of Planck's constant?
2. What is a stationary orbit?
3. What are degenerate orbitals?
4. Who proposed the principal Quantum number?
5. What are the limits of azimuthal Quantum number for a given 'n'?
6. What are upper and lower limits of m for l = 4?
7. How many 'm' values are possible for l = 3
8. What is the shape of '1s' orbital?
9. What is nodal plane?
10. Write the designations of any two d-orbitals?
11. How are the three p-orbitals designated?
12. What is the unit of electron affinity?
SECTION - III
Long Answer Questions (4 Marks Each)
1. State The Postulates of Bohr's model. What are the defects of Bohr's model?
2. Explain the important features of Rutherford's model of atom. Discuss its draw-backs?
3. State and explain with one example The Hund's rule of maximum multiplicity?
4. Define the ionization energy and mention the factors that influence it.
5. Explain the four Quantum numbers briefly.
6. State and explain Pauli's exclusion principle with example.
7. Discuss the features of modern atomic structure.
SECTION - IV
DIAGRAMS (5 Marks Each)
1. Draw the shapes of s and p orbitals?
2. Draw the shapes of five 'd' orbitals?
3. Draw the diagram showing the sequence of filling of various atomic orbitals?
0 comments:
Post a Comment