12.1 Shapes of Orbitals

  Structure of Atom

• The three dimensional region of space around the nucleus where there is maximum probability of finding the electron is callled atomic orbital.
• The square of the wave function (${\psi ^2}$) at a point gives the probability density of the electron at that point and represented by radial probability curve.
• For 1s orbital the radial probability curve shows that the probability of finding the electron in 1s orbital increases as we move away from the nucleus and reaches a maximum at a certain distance (= 0.0529 nm or 52.9 pm for hydrogen atom) and then decreases as we go further away from it and at a certain distance it becomes close to zero.
• For 2s orbital the probability density first decreases sharply to zero and again starts increasing. After reaching a small maxima it decreases again and approaches zero as the value of r increases further.
• A Radial node is a region in space where the probability of finding the electron is close to zero.
• The total number of nodes are (n–1), which is sum of l angular nodes and (n – l – 1) radial nodes.
• Angular node is define as number of planes in which probability of finding electrons is zero. Number of Angular node is given by l.
• Boundary Surface Diagram give the good picture of shape of orbitals. It reperesent the region in space around nucleus where probability of finding electron is 90%.