## NCERT Solutions for Chemistry Class 11 – Unit 2- Shapes of Orbitals

*Chemistry notes for Class 11*:** The s Orbital**

An orbital with ** l** = 0 (angular momentum quantum number, which describes the shape of an orbital) and thus,

**= 0 (a magnetic quantum number which describes the orientation of orbital in space around the nucleus) is called**

*m***. Since**

*s*orbital**has one value this means the**

*m***orbital can have only one orientation and the**

*s***can be defined completely by a single value i.e. radius. So, the**

*sphere***. The size of**

*s*orbital are spherically symmetrical about the nucleus**orbital depends on the value of the principal quantum number. Therefore 1**

*s***orbital is smaller than 2**

*s***orbital, but both are spherical in shape.**

*s*Shapes and size of** s **orbitals

The symmetry of ** s** orbitals along three axes x,y,z

Between two regions of the high probability of electrons is a spherical **node**, it is the region where the probability of finding electrons is zero.

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**The p Orbital**

The maximum value of ** l** is

**so the only levels with**

*n*– 1,**= 2 or higher have a**

*n***orbital. 2**

*p***orbital is closest to the nucleus. Unlike**

*p***orbitals,**

*s***orbitals have different spatial orientations. If**

*p***=2, the values of**

*n***= 2-1 i.e. 1. So, the values of**

*l***will be -1, 0, +1, i.e. there are three values which suggest that there are three**

*m***orbitals because a**

*p***number of**The

*m*values give the number of orbitals.**orbital has two regions or lobes of the high probability of finding electrons, one on either side of the nucleus. This makes the orbital look like two pears joined together at their narrow ends. The whole arrangement appears like a dumb- bell.**

*p***The nucleus lies at the nodal plane of this dumbbell shaped orbital.**

While identical in size, shape, and energy, the three p orbitals differ in orientations. The ** p_{x }**orbital lies along the x-axis,

**orbital lies on y-axis and**

*p*_{y }**orbital lies along z-axis. Similar to the pattern of**

*p*_{z}**orbital, the a**

*s***orbital is bigger than**

*3p***orbital and**

*2p***orbital is bigger than**

*4p***orbital and so forth.**

*3p**Watch, learn and practice questions of Dalton’s Atomic Theory, click Class 11 Chemistry for more details.*

**The d Orbital**

For ** n** = 3,

**can have three values, 0, 1, 2. We have discussed the shape and orientations of orbitals when**

*l***= 1 and**

*n***= 2. When**

*n***=3, then**

*n***= 3-1 i.e. 2. This means**

*l***-2, -1, 0, +1, +2, hence there will be five**

*m***orbitals. The five**

*d***orbitals possess equal energies and differ only in their orientations in space.**

*d***Four of the five**orbitals have four lobes (a cloverleaf shape) with two mutually perpendicular nodal planes between them and nucleus at the junction of the lobes.

Three of these orbitals lie in the xy, xz and yz planes, with their lobes between the axes, and are called ** d_{xy}**,

**, and**

*d*_{xz}**orbitals. A fourth,**

*d*_{yz}

*d*_{x}

*2*

_{– y}**orbital, also lies in the xy plane, but its lobes are along the axes. The fifth**

*2***orbital, the**

*d*

*d*_{z}**, has two major lobes along the z-axis, and a donut-shaped region in the center. An electron in the**

*2***orbital spends equal time in all of its lobes.**

*d***Orbitals with higher values**

When ** n** = 4, then

**= 3, this means**

*l***= -3, -2, -1, 0, 1, 2, 3. Hence there are seven**

*m***orbitals. Each**

*f***orbital has a complex, multi-lobed shape with several nodal planes.**

*f**f *orbitals

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