2.4-2.5
Your guide: Miss SanaCounts atoms the way you count rupees: carefully.
Every electron has an address. It takes four numbers to write it.
Let us learn to read these four numbers.
Schrodinger's model needs three quantum numbers: n, l and m. They give the size, shape and orientation of an orbital.
The principal number n is 1, 2, 3, 4…, called K, L, M, N. It gives size and energy.
A bigger n means higher energy and an electron farther from the nucleus.
A shell holds at most 2n2 electrons: 2, 8, 18, 32 for K, L, M, N.
The azimuthal number l runs from 0 to n − 1. It gives the shape.
l = 0, 1, 2, 3 are s, p, d, f. A subshell holds 2(2l + 1): 2, 6, 10, 14.
The number of subshells in a shell equals the shell number.
The magnetic number m gives the orientation of an orbital. It has 2l + 1 values.
So s has 1 orbital, p has 3, d has 5 and f has 7.
Orbitals of one subshell have the same energy. They are called degenerate.
An electron also spins. The spin number s is +½ or −½.
Three numbers describe an orbital. The fourth tells apart the two electrons in it.
In shell n there are n subshells and n2 orbitals, holding 2n2 electrons.
An orbital is the 3D region where the chance of finding the electron is greatest.
An s orbital is spherical. It grows bigger as n grows.
A p orbital has two lobes on an axis. They are pₓ, p_y and p_z.
The five d orbitals have different shapes. The f orbitals are very complicated.
Step 1 / 7
Every electron has an address. It takes four numbers to write it.
Let us learn to read these four numbers.
Schrodinger's model needs three quantum numbers: n, l and m. They give the size, shape and orientation of an orbital.
The principal number n is 1, 2, 3, 4…, called K, L, M, N. It gives size and energy.
A bigger n means higher energy and an electron farther from the nucleus.
A shell holds at most 2n2 electrons: 2, 8, 18, 32 for K, L, M, N.
The azimuthal number l runs from 0 to n − 1. It gives the shape.
l = 0, 1, 2, 3 are s, p, d, f. A subshell holds 2(2l + 1): 2, 6, 10, 14.
The number of subshells in a shell equals the shell number.
The magnetic number m gives the orientation of an orbital. It has 2l + 1 values.
So s has 1 orbital, p has 3, d has 5 and f has 7.
Orbitals of one subshell have the same energy. They are called degenerate.
An electron also spins. The spin number s is +½ or −½.
Three numbers describe an orbital. The fourth tells apart the two electrons in it.
In shell n there are n subshells and n2 orbitals, holding 2n2 electrons.
An orbital is the 3D region where the chance of finding the electron is greatest.
An s orbital is spherical. It grows bigger as n grows.
A p orbital has two lobes on an axis. They are pₓ, p_y and p_z.
The five d orbitals have different shapes. The f orbitals are very complicated.
Q1. Quick Check 2.3 (b)(i): n = 2 and l = 1. How many orientations in space?
2l + 1 = 3: m = −1, 0, +1. Three orientations.
Q2. Quick Check 2.3 (b)(iii): l = 2. Find the values of m and the electrons.
m = +2, +1, 0, −1, −2. Five orbitals hold 5 × 2 = 10 electrons.
✗ “An orbital is a circular path.”
✓ In this chapter, an orbital is a 3D region of high chance of finding the electron.
✗ “l can equal n.”
✓ l stops at n − 1. For n = 2, l is 0 or 1.
1. How many orbitals are in a d subshell?
(c) 2l + 1 = 5.
2. How many electrons fit in the M shell?
(b) 2n2 = 2 × 9 = 18 for n = 3.
3. Which quantum number gives the shape of an orbital?
(b) The book says l describes shape.
4. The three p orbitals are oriented:
(c) This is the book exercise MCQ.
5. Spin quantum number can be:
(a) Clockwise and anticlockwise spin.
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