Electron clouds: shapes of s, p and d orbitals in 3D
See the 3D shapes of the 1s, 2s, 2p, 3s, 3p and 3d orbitals as clouds of dots, with the nodes and the red and blue lobes, and the radial probability graph. Free for every student.
Also searched as: orbitals · shapes of atomic orbitals · s p d orbitals · atomic orbitals 3d · quantum numbers class 11 · nodes in orbitals
About this experiment
| Subject | Chemistry |
|---|---|
| Class | 11 |
| Unit | 2. Structure of Atom |
| NCERT section | 2.6 |
| Level | NCERT level |
| Time | about 15 minutes |
| Access | Free, no card needed |
Aim
To see the three-dimensional shapes of s, p and d orbitals, to read their quantum numbers, and to understand what nodes are.
Theory
An orbital is not a path. It is the region around the nucleus where the electron is most likely to be found. The dots in the picture are many snapshots of where the electron could be: where the dots are dense the electron is found often.
Each orbital has three quantum numbers. The principal quantum number n (1, 2, 3 ...) gives the size and energy. The azimuthal quantum number l (0 to n − 1) gives the shape: l = 0 is an s orbital (sphere), l = 1 is a p orbital (dumbbell), l = 2 is a d orbital (four lobes or a dumbbell with a ring). The magnetic quantum number m (−l to +l) gives the direction in space, so there are 1 s, 3 p and 5 d orbitals in a subshell.
A node is a place where the electron is never found. The number of radial (spherical) nodes is n − l − 1 and the number of angular nodes (planes or cones) is l, so the total number of nodes is n − 1. A 2s orbital has one spherical node, a 2p orbital has one nodal plane.
Formulas used
- n = 1, 2, 3 ...; l = 0 to n − 1; m = −l to +l
- radial nodes = n − l − 1
- angular nodes = l
- total nodes = n − 1
- orbitals in a subshell = 2l + 1 (s: 1, p: 3, d: 5)
- E_n = −13.6 / n² eV (hydrogen)
- probability in a thin shell = 4πr² R(r)² dr
Procedure: what to do in the virtual lab
- Choose 1s and look at the graph: the chance is highest at one a₀ (the Bohr radius).
- Choose 2s: find the spherical node (a gap with no dots) and the dip to zero in the graph.
- Choose the 2p orbitals: two lobes with a nodal plane in between. Compare pz and px.
- Compare 3s, 3p and 3d: count the nodes and check that the total is n − 1 = 2.
- Switch the colours off and on and see which lobes have the same sign.
Observations to make
- The orbital grows bigger and has more nodes as n increases.
- The s orbitals are spherical, the p orbitals have two lobes along an axis and the d orbitals have four lobes (except dz²).
- In the 2s graph the maximum is further away from the nucleus than in 1s, but there is also a small peak close to the nucleus (the electron "penetrates").
What you can change in this experiment
- Orbital: 1s / 2s / 2p (pz) / 2p (px)
- Picture: Boundary surface (clear lobes) / Probability cloud (dots)
- Number of dots (more dots = clearer cloud)
- Colour lobes by sign of the wave (red +, blue −) (on / off)
- Turn the orbital slowly (on / off)
Viva questions on Electron clouds
Questions an examiner may ask in the Class 11 chemistry practical. Run the experiment in the lab to find the answers yourself, then check them in the Learn tab.
- What is the difference between an orbit and an orbital?
- How many orbitals are there in the 3d subshell and how many electrons can they hold?
- How many radial and angular nodes does a 3p orbital have?
- What do the quantum numbers n, l and m tell us?
Frequently asked questions
What is the aim of the Electron clouds experiment?
To see the three-dimensional shapes of s, p and d orbitals, to read their quantum numbers, and to understand what nodes are.
Which formulas are used in the Electron clouds experiment?
n = 1, 2, 3 ...; l = 0 to n − 1; m = −l to +l; radial nodes = n − l − 1; angular nodes = l; total nodes = n − 1; orbitals in a subshell = 2l + 1 (s: 1, p: 3, d: 5)
What viva questions are asked on Electron clouds?
What is the difference between an orbit and an orbital? How many orbitals are there in the 3d subshell and how many electrons can they hold? How many radial and angular nodes does a 3p orbital have? What do the quantum numbers n, l and m tell us?
How do I do the orbitals experiment for Class 11 online?
Open the Electron clouds virtual lab on PractiSci, follow the procedure above, change the values and read the live graph. It matches the Class 11 chemistry practical, with the aim, theory, observations and viva questions on this page.
Can I do the Electron clouds experiment online?
Yes. Open it as a 3D virtual lab in your browser or on your phone, change the values and read the results from live graphs. This lab is free.
Syllabus: Class XI Chemistry, Chapter 2 — Structure of Atom, §2.6 (quantum mechanical model of the atom)
What you do in the lab
Change the controls and watch the chemistry behave in real time in 3D. Live readouts and graphs show the numbers behind it, and the Learn tab has the theory, procedure, observations and viva questions. Works on a phone or a laptop, in English and Hindi.
Topics: orbital · s orbital · p orbital · d orbital · quantum numbers · electron cloud · node · probability density · structure of atom
More from this unit
- Build an atom: protons, neutrons and electrons
- Schrödinger wave equation: wave function, probability and quantised energy
- Electron, proton and neutron: how they were discovered (beams in electric and magnetic fields)
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