NEET Chemistry Atomic Structure
Atomic Structure PDF Notes, Important Questions and Synopsis
SYNOPSIS
Dalton’s atomic theory:
Dalton’s atomic theory is based on the law of conservation of mass and the law of definite proportions. He also proposed the law of multiple proportions.
Thomson’s model of atom:
- It is also known as watermelon model or plum pudding model.
- According to this model, the atom is a positive sphere in which negative charges are distributed.
Rutherford alpha scattering experiment:
- This experiment was performed to understand the structure of an atom.
- This model concludes that most of the part of an atom is empty and each atom consists of a heavy positively charged nucleus.
Particle |
Mass (amu) |
Charge |
Discoverer |
Electron |
1.0073 |
+1 |
JJ Thomson |
Proton |
1.0087 |
0 |
Goldstein |
Neutron |
0.0005 |
−1 |
Chadwick |
Bohr’s model of atom:
- Electrons orbit the nucleus in orbits which have a set size and energy.
- The lowest energy is found in the smallest orbit.
- Radiation is absorbed or emitted.
Electromagnetic radiation:
- Wavelength: It is the distance between successive points of equal phases of a wave.
- Frequency: It is the number of cycles or oscillations or vibrations of wave motion in unit time.
- Velocity: It is the distance travelled by the wave in one second.
- Wave number: It is defined as the number of waves in unit wavelength.
Heisenberg’s uncertainty principle:
The uncertainty principle says that we cannot measure the position and momentum of the particle with absolute precision.
Bohr–Sommerfield model:
- According to this model, the path of an electron around the nucleus is an ellipse with the nucleus at one of its foci.
- The angular momentum of an electron in a closed elliptical path is also quantised.
Orbital:
An orbital is a three-dimensional region in which the probability of finding an electron is maximum.
Quantum numbers:
Principal quantum number:
- It is denoted by n.
- n = 1, 2, 3, 4 … ∞
- n = 1 K shell; n = 2 L shell
- n = 3 M shell; n = 4 N shell
- As the value of ‘n’ increases, the energy of the electron increases.
Azimuthal or angular quantum number:
- It is denoted by l.
- The values of l are from 0 to (n-1)
- l = 0 s subshell; l = 1 p subshell
- l = 2 d subshell; l = 3 f subshell
- The value of ‘l’ signifies the shape and energy level of subshells in a major energy shell.
Magnetic quantum number:
- It is denoted by ml.
- The values of ml lie from –l to +l.
- The values of ml signify the possible number of orientations of subshells.
Spin quantum number:
- It is denoted by ms.
- The values of ms are +1/2 and −1/2.
- The values of ms signify the direction of rotation or the spin of an electron in its axis during motion.
Subshell |
Shape of orbital |
s |
Spherical |
p |
Dumbbell |
d |
Double dumbbell |
f |
Diffused shape |
Pauli’s exclusion principle:
- It is impossible for two electrons of an atom to have all its four quantum numbers same.
- Maximum number of electrons in a shell can be 2n2.
- Maximum number of electrons in a subshell can be 2 only.
Aufbau principle:
- Orbitals with lower energy level are filled first.
(n+l) rule:
- The subshell with lower values of (n+l) possesses lower energy.
- If (n+l) for two orbitals are the same, the one with lower value of n possesses lower energy and should be filled first.
Paramagnetism:
A substance whose molecules, ions or atoms have unpaired electrons is paramagnetic.
Diamagnetism:
Molecules, ions or atoms having no unpaired electrons are diamagnetic.
Videos
- 900 nm wavelength radiation is used in the treatment to relieve muscle pain. So which of the following is similar to this wavelength radiation? (A) Balmer (infinity to 2) (B) Lyman (infinty to 1) (C) paschen (5 to 3) (D) paschen (infinity to 3)
- Solve this plz !
- what is atom
- The value of Planck’s constant is 6.63 x 1034 Js. The velocity of light is 3.0 x 108 ms1. Which value is closest to the wavelength (in nanometres) of a quantum of light with frequency of 8 x 1015 s1? 1) 3 x 107 2) 2 x 1025 3) 5 x 1018 4) 4 x 101
- ⭕ Answer this question...given Thanks ☺️
- Number of elements in second period of periodic table if spin quantam number could have values _1/2 ,0,1/2
- please answer this
- please answer this
- please answer this
- please answer this
Kindly Sign up for a personalised experience
- Ask Study Doubts
- Sample Papers
- Past Year Papers
- Textbook Solutions
Sign Up
Verify mobile number
Enter the OTP sent to your number
Change