Summary of "Probability distribution curves | Atomic structure - Bsc 1st year inorganic chemistry"
Summary of "Probability distribution curves | Atomic Structure - Bsc 1st year inorganic chemistry"
This lecture explains the concept of radial probability distribution curves in the context of Atomic Structure, focusing on the probability of finding an electron at various distances from the nucleus. The key ideas, concepts, and methodology are outlined below.
Main Ideas and Concepts
- Electron Probability Function
- Defines the probability of finding an electron in a three-dimensional space around the nucleus.
- Denoted by a capital \( D \).
- The probability is non-zero within a spherical shell of radius \( r \) and thickness \( dr \) around the nucleus.
- Mathematical Representation
- The Electron Probability Function \( D \) for a thin spherical shell is given by: \[ D = |\psi|^2 \times \text{volume of shell} \]
- Volume of the shell = surface area of the sphere \( \times \) thickness \( dr \).
- Surface area of a sphere = \( 4 \pi r^2 \).
- So, \[ D = |\psi|^2 \times 4 \pi r^2 dr \]
- Here, \( |\psi|^2 \) is the square of the wavefunction, representing the probability density.
- Radial Wavefunction and Radial Probability Distribution
- The Radial Wavefunction \( R_{nl}(r) \) depends on quantum numbers \( n \) (principal) and \( l \) (azimuthal).
- The radial probability distribution is obtained by replacing \( |\psi|^2 \) with \( |R_{nl}(r)|^2 \), multiplied by the volume element \( 4 \pi r^2 dr \).
- This gives the probability of finding an electron at a distance \( r \) from the nucleus within a small shell thickness \( dr \).
- Radial Probability Distribution Curve
- Plotting radial probability (y-axis) against distance \( r \) from the nucleus (x-axis) yields the Radial Probability Distribution Curve.
- The peak of this curve indicates the most probable distance where the electron is likely to be found.
- Probability decreases on either side of this peak but is never zero except at certain points called nodes.
- Electron Charge Density and Shell Volume
- Electron charge density decreases with increasing distance from the nucleus because it is inversely proportional to the size (radius).
- However, the volume of the spherical shell increases with radius, which affects the overall probability.
- Examples of Radial Probability Distribution Curves for Different Orbitals
- Curves for 1s, 2s, 2p, 3s, 3p, and 3d orbitals were discussed.
- As you move to orbitals with higher principal quantum numbers, the curves spread out more, indicating larger orbital sizes.
- The area under the curve increases from left to right, reflecting the increasing spatial extent of orbitals.
- Radial Nodes
- Radial nodes are points where the radial probability (and thus electron density) is zero.
- The number of radial nodes for an orbital is given by: \[ \text{Number of radial nodes} = n - l - 1 \]
- Examples:
- 1s Orbital: \( n=1, l=0 \Rightarrow 0 \) radial nodes
- 2p Orbital: \( n=2, l=1 \Rightarrow 0 \) radial nodes
- 3s orbital: \( n=3, l=0 \Rightarrow 2 \) radial nodes
- 3p orbital: \( n=3, l=1 \Rightarrow 1 \) radial node
- 3d Orbital: \( n=3, l=2 \Rightarrow 0 \) radial nodes
- Orbitals with more radial nodes (e.g., 3s) are larger and more diffused compared to those with fewer nodes (e.g., 1s).
Methodology / Instructions Presented
- To calculate the electron probability in a spherical shell:
- Identify the radius \( r \) and thickness \( dr \) of the shell.
- Calculate the volume of the shell: \( 4 \pi r^2 dr \).
- Obtain the Radial Wavefunction \( R_{nl}(r) \) for the orbital.
- Square the Radial Wavefunction: \( |R_{nl}(r)|^2 \).
- Multiply \( |R_{nl}(r)|^2 \) by the volume of the shell to get the radial probability distribution:
Category
Educational
