Shapes of Orbitals

Atomic orbitals are regions of space around the nucleus of an atom where there is a high probability of finding an electron. Each type of orbital possesses a unique three-dimensional shape that dictates the behavior of electrons within it.

s Orbitals

The simplest type of orbital is the s orbital. Electrons residing in an s orbital are most likely to be found within a spherical region surrounding the nucleus. Imagine taking numerous snapshots of an electron’s location in an s orbital over a period of time and overlaying them. The resulting image, known as a probability density, would resemble a spherical cloud. For simplicity, we represent this electron cloud as a sphere, which we call an s orbital.

There is one s orbital for each energy level, starting with the first energy level (n=1). These s orbitals are designated as 1s, 2s, 3s, and so on, corresponding to the first, second, and third energy levels, respectively. As the principal quantum number (n) increases, the size of the s orbitals also increases, while maintaining the same spherical shape.

p Orbitals

Orbitals occupied by p electrons have a different shape compared to s orbitals. Starting from the second energy level (n=2), there are three p orbitals. Each p orbital consists of two lobes, resembling a dumbbell or a balloon tied in the middle. These three p orbitals are oriented perpendicularly to each other along the x, y, and z axes around the nucleus. Similar to s orbitals, the shape of p orbitals remains consistent across different energy levels, but their volume increases at higher energy levels.

d Orbitals

At the third energy level (n=3), we encounter d orbitals. There are five d orbitals, each with more complex shapes. Four of the five d orbitals have a four-lobed structure, aligned along or between different axes. The fifth d orbital has two lobes with a doughnut-shaped ring around its center.

f Orbitals

The fourth energy level (n=4) introduces f orbitals. There are seven f orbitals, each with complex shapes that are beyond the scope of this discussion.

Learn more

Orbital Capacity and Electron Spin

The Pauli Exclusion Principle states that each orbital can hold a maximum of two electrons. Electrons also exhibit a property called spin, which can be either spin-up or spin-down. When two electrons occupy the same orbital, they must have opposite spins to minimize repulsion. This is analogous to two magnets aligning with opposite poles. We represent electron spins using arrows, with an upward arrow (↑) indicating spin-up and a downward arrow (↓) indicating spin-down (Figure 2.15).

Number of Electrons in Sublevels

Each sublevel (s, p, d, f) can accommodate a specific number of electrons. An s sublevel can hold a maximum of two electrons. Since each p orbital can hold two electrons and there are three p orbitals, a p sublevel can hold a maximum of six electrons. Similarly, d sublevels can hold up to ten electrons, and f sublevels can hold up to fourteen electrons.

Learn more