Shortcut Methods
JEE Main & CBSE Board Exams:
1. Determining Number of Protons, Neutrons, Electrons:
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Atomic number (Z) represents the number of protons in an atom.
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Mass number (A) represents the total number of protons (Z) and neutrons (N) in an atom.
- Number of electrons (E) is equal to the number of protons (Z) for a neutral atom.
2. Average Atomic Mass:
The average atomic mass of an element is a weighted average of the masses of its naturally occurring isotopes, taking into account their relative abundances.
Formula:
3. Bohr’s Model Calculations:
- Radius of orbit (r) for the nth orbit:
- \(n\) is the principal quantum number.
- \(h\) is the Planck's constant.
- \(k\) is the Coulomb's constant.
- \(m_e\) is the electron mass.
- \(Z\) is the atomic number.
- Energy of the electron in the nth orbit (E):
- \(e\) is the elementary charge.
- \(\varepsilon_0\) is the permittivity of free space.
- Wavelength of emitted photon ((\lambda)) during transition between two orbits (n1 to n2):
- \(R_H\) is the Rydberg constant.
