• Bohr’s model of atom: Electrons are present in stationary states. The electron moves to higher
energy level if it absorbs energy in the form of electromagnetic energy or moves to a lower
energy state by emitting energy in the form of electromagnetic energy of appropriate frequency.
• Atomic line spectra arise because of absorption /emission of certain frequencies of light energy.
• It is not possible to measure accurately the position and velocity of an electron simultaneously.
• The space around the nucleus where the probability of finding the electron is maximum is called
orbital.
• The three quantum numbers n, l, ml describe the energy, shape and orientation respectively, of
an atomic orbital.
• Spin is an intrinsic property of an electron.
• The arrangement of electrons in shells, sub-shells and orbitals in an atom is called the electron
configuration.
• According to Pauli Exclusion Principle no two electrons of the same atom can have all the four
quantum numbers same.
• Aufbau principle: The lowest-energy orbitals are filled first.
• Hund’s rule: The orbitals of equal energy (degenerate) are occupied with one electron each
before pairing of electrons starts.
1. What information does the electronic configuration of an atom provide? (AS1
)
2. Rainbow is an example for continuous spectrum – explain. (AS1
)
3. What is absorption spectrum? (AS1
)
4. What is an orbital? How is it different from Bohr’s orbit?(AS1
)
5. Explain the significance of three Quantum numbers in predicting the positions of an electron
in an atom.(AS1
)
6. What is nl x
method? How is it useful? (AS1
)
7. What is emission spectrum?
8. Which electronic shell is a higher energy level K or L? (AS2
)
1. Answer the following questions.
a. How many maximum number of electrons can be accommodated in a principal energy level?
b. How many maximum number of electrons can be accommodated in a sub shell??
c. How many maximum number of electrons can be accommodated in an orbital??
d. How many sub shells are present in a principal energy level?
e. How many spin orientations are possible for an electron in an orbital? (AS1
)