What is the difference between s and p orbitals?

Let's start with neon, the attractive force of 10 protons, screened to varying degrees by the 9 other electrons, must be overcome in order to remove the outermost p electron, this requires 21.5 eV. There are only 9 protons holding the outermost electron in fluorine in place, again screening plays a role, but with only 9 protons it is easier to remove fluorine's outermost electron (18.7 eV). This trend of decreasing IP continues for the remaining elements with 2p electrons as we move to the left across this row of elements.

The corresponding 2s IP's are much higher. For example, the neon 2s IP=48.5 eV. To measure this IP, we have already removed neon's 6 outermost 2p electrons. The 2s electron is still held in place by 10 protons, but now only 3 other electrons remain to screen these protons. Consequently it is much more difficult to remove one of neon's inner 2s electrons. As we move to the left across this row of elements looking at the 2s IP's we see a trend similar to what we saw with the 2p IP's, but 2 factors are now involved. It get's easier to remove the 2s electron as the number of protons decreases (reduced nuclear attraction) and as the number of already removed outer 2p electrons becomes smaller (more screening).

The same trends are observed in the n=3 series, but the IP's are lower to start with and differences between successive ionizations are compressed because the number of protons, and therefore the number of screening electrons, has increased by 8.

Everytime we add a proton to the nucleus, we also add an electron to keep the charge balanced. In the case of neon, that 10th electron does not feel the full attraction of the 10 protons - the other electrons screen this last electron from the nucleus. The bigger and bigger we make our nucleus, the more electrons there are between the last electron we added and the nucleus, therefore that last electron feels less and less of a full proton's attraction, as the number of electrons between it and the nucleus increases.

Here is a good example of compression. The first IP of neon is 21.5 ev, the IP to pull out a fifth electron (after the first 4 electrons have already been removed) is 126.2 eV - about 6 times more energy is required. Now consider radon, its first IP is only 10.7 eV. That electron in radon has so many more electrons between it and the nucleus (76 more to be exact) that screen that last electron from the nucleus, that it is much easier to remove that outermost electron in radon. The fifth IP for radon is 55 eV - only about 5 times more energy (less than 6) is required here, that is compression.

Here is a link to a nice, thorough discussion on ionization energies and their trends that you may find of interest.

Finally here is a pictorial representation of what we have been discussing.

Note how the spacing between the lines decreases as we move to higher atomic number; also note that the slope of the lines tends to increase as the atomic numbers increases. Both of these observations illustrate what we have been discussing. As the atomic number increases there are more and more electrons between the outermost electron and the nucleus making it easier to remove that last electron and making the both the absolute and relative differences between successive ionizations (e.g. 1st IP and 2nd IP, 1st IP and 5th IP, etc.) smaller.

Atomic orbitals are mathematical functions that describe the wave nature of electrons (or electron pairs) in an atom.

They offer a way to calculate the probability of finding an electron in a specified region around the nucleus of the atom.

Orbitals Chemistry

There are four different kinds of orbitals, denoted s, p, d and f each with a different shape. Of the four, s and p orbitals are considered because these orbitals are the most common in organic and biological chemistry. An s-orbital is spherical with the nucleus at its centre, a p-orbitals is dumbbell-shaped and four of the five d orbitals are cloverleaf shaped. The fifth d orbital is shaped like an elongated dumbbell with a doughnut around its middle. The orbitals in an atom are organized into different layers or electron shells.

The Shape of s Orbitals

The boundary surface diagram for the s orbital looks like a sphere having the nucleus as its centre which in two dimensions can be seen as a circle.
Hence, we can say that s-orbitals are spherically symmetric having the probability of finding the electron at a given distance equal in all the directions.
The size of the s orbital is also found to increase with the increase in the value of the principal quantum number (n), thus, 4s > 3s> 2s > 1s.

The Shape of p Orbitals

Each p orbital consists of two sections better known as lobes which lie on either side of the plane passing through the nucleus.
The three p orbitals differ in the way the lobes are oriented whereas they are identical in terms of size, shape, and energy.
As the lobes lie along one of the x, y or z-axis, these three orbitals are given the designations 2px, 2py, and 2pz. Thus, we can say that there are three p orbitals whose axes are mutually perpendicular.
Similar to s orbitals the size, and energy of p orbitals increase with an increase in the principal quantum number (4p > 3p > 2p).

The Shape of d Orbitals

The magnetic orbital quantum number for d orbitals is given as (-2,-1,0, 1,2). Hence, we can say that there are five d-orbitals.
These orbitals are designated as dxy, dyz, dxz, dx2–y 2 and dz2.
Out of these five d orbitals, the shapes of the first four d-orbitals are similar to each other, which is different from the dz2 orbital whereas the energy of all five d orbitals is the same.

Solved Example

Assuming 2s-2p mixing is NOT operative, the paramagnetic species among the following is :
(A) Be2
(B) B2
(C) C2
(D) N2

Solution:

The answer is C2
C2 = valence electrons =8
(σ2s)2(σ∗2s)2(σ2pz)2(π2px)1(π2py)1
Because if the question says 2s-2p orbital intermixing is not operative it indicates you to fill the molecular orbitals according to the energy order of the system having electrons >14
The electrons are unpaired in a bonding molecular orbital. Rest in all other molecules the electrons are paired all others are diamagnetic.

Frequently Asked Questions – FAQs

How many orbitals are there in chemistry?

The four different orbital forms (s, p, d, and f) have different sizes and one orbital will accommodate up to two electrons at most. The orbitals p, d, and f have separate sub-levels and will thus accommodate more electrons. As shown, each element’s electron configuration is unique to its position on the periodic table.

How do orbitals work?

An atomic orbital is a mathematical term in atomic theory and quantum mechanics that describes the wave-like behaviour of either one electron or a pair of electrons in an atom. Every such orbital will occupy a maximum of two electrons, each having its own quantity of spin.

How many orbitals are there?

The s sublevel has only one orbital, so max. 2 electrons can be present. The p sublevel has 3 orbitals, so max. 6 electrons can be present. The d sublevel has 5 orbitals, so max. 10 electrons can be present. And the 4 sub-levels have seven orbitals, and they can hold max of 14 electrons.

Why is the s orbital spherical?

All s orbitals are shaped spherically and have spherical symmetry. That means the function of the wave will depend only on the distance from the nucleus and not on the direction. For any particle, as the central quantum number of the orbital decreases, the size of the orbital decreases, but the geometry stays spherical.

What is sigma and pi bond?

Sigma and pi bonds are formed by atomic orbital overlap. Sigma bonds are formed by overlapping end-to-end and Pi bonds occur where one atomic orbital lobe overlaps another. As seen along the axis of the bond, both derived their names from the Greek letters and the bond.

What does P orbital stand for?

The s, p, d, and f, respectively stand for sharp, primary, diffuse and fundamental. The letters and words refer to the visual impression left by the spectral lines’ fine structure that occurs because of the first relativistic corrections, particularly the spin-orbital interaction.

Which orbitals have the highest energy?

The orbital 1s hold the highest energy. You will appreciate it by talking of different things: But first let’s be super clear: an electron’s energy is the energy it will take to pull it out of the electrical bubble of the atom.

What is the difference between a shell and an orbital?

A shell in an atom is a set of subshells of the same quantum number theory, n. Orbitals contain two electrons each, and electrons are part of the same orbital in an orbital of the same definition of size, angular momentum size, and magnetic quantum number.

What is one difference between the s and p sublevel of an atom?

There are four different types of sublevels (s,p,d,f). The p, d, and f sublevels have multiple orbitals and can hold more electrons Each orbital within a sublevel can hold a maximum of two electrons. The s sublevel is just 1 orbital and only holds 2 electrons.

Why is s orbital lower in energy than p?

Because it is less effectively shielded, a 2s electron experiences a higher effective nuclear charge and is held closer to the nucleus than a 2p electron which gives the 2s orbital a lower energy.

What is the meaning of p orbital?

noun. ˈpē- often ital p. : the orbital of an electron shell in an atom in which the electrons have the second lowest energy.

What is the meaning of s orbital?

The s orbital is a spherically-shaped region describing where an electron can be found, within a certain degree of probability. The shape of the orbital depends on the quantum numbers associated with an energy state. All s orbitals have l = m = 0, but the value of n can vary.