Atomic Structure of Elements
The atomic structure of a material must be studied in order to understand its behaviour as a conductor, insulator, or semi-conductor. Every material is assumed to be made up of the tiniest and tiniest indivisible particles that cannot be further divided, which are referred to as Atoms. A number of atoms make up each element. An atom of any element consists of:
(a) electrons which are
negatively charged, light in weight and movable.
(b) protons which are
immovable
(c) neutrons have no
charge but heavy and immovable.
The negative electrical charge of each electron is 1.602 x 10-19. Coulombs and protons in the nucleus have the same positive charge. A force of attraction exists between the oppositely charged electrons and the nucleus because opposite charges attract. The centrifugal force generated by the migration of electrons around the nucleus balances the attraction force. Electrons are extremely small particles with minimal mass, and hence can be said to have no mass when compared to the mass of the nucleus. A cluster of protons and neutrons makes up the nucleus of an atom. The charge of a neutron is 0 (zero). The number of protons in the nucleus of an atom equals the number of orbiting electrons for that atom.
The number of negatively charged electrons in the nucleus of an atom is always equal to the amount of positively charged protons. For all sorts of materials, these electrons fall into orbits that are well-defined. If a negatively charged electron moves out of its orbit due to some external force, it is replaced by another electron in the same orbit. As illustrated in Figure, the electrons in every orbit are generally balanced.
|
Figure: Sample Atomic Structure |
To balance the electrical charge in a more complicated atom, the number of
electrons required rises, and the orbit expands to accommodate the electrons.
In a hydrogen atom, there is only one electron that occupies a single
orbit. In the same way, two electrons in the helium atom share the same orbit.
However, because the Lithium atom has three electrons, only two electrons can
occupy the initial orbit. Even in more complicated atoms, the orbital
arrangement is fixed. The first, innermost orbit may hold a maximum of two
electrons, while the last, outermost orbit can hold up to eight electrons. The
number of electrons in the orbits between the innermost and the outermost may
vary, but the outermost orbit never has more than eight electrons. The number
of electrons in the outermost orbit determines the properties, which are
categorized as conductors, insulators, or semi-conductors.
Electronic Configuration :
The magnitude of the positively charged proton and negatively charged electron is equal to 1.6 x 10-19 Coulomb. A proton or neutron has a mass of 1.672 x 10-27 kg, while an electron has a mass of 9.107 x 10-31 kg. As a result, a proton weighs 1836 times more than an electron. The orbit in which electrons revolve is referred to as the shell. The planes of different shells differ. The number of electrons that can fit in each shell is 2n2, where n is the number of shells starting from the innermost. Figure 1 shows a basic shell configuration.
Figure: Sample Shell Configuration
Potassium, for instance,
has 19 protons in its nucleus and 19 electrons in its orbit. As a result, its
atomic number is 19. The number of electrons in the orbit is calculated using
the formula 2n2. as:
(a) innermost orbit (K shell) 2n2 = 2 X 12 = 2 electrons
(b) second orbit (L
shell) 2n2 = 2 X 22 = 8 electrons
The balance is nine. The third orbit (M shell) has a capacity of 2 x 32 = 18 electrons, yet there are only nine. In order for the shell to remain stable, an even number of electrons must be present. As a result, 8 electrons are in the M shell and one in the N shell.
Consider the atomic
number 32 of Germanium. In this orbit, there are 32 electrons. The number of
electrons in each shell can be calculated using the same formula:
K shell = 2n2 = 2 x 12 = 2 electrons
L shell = 2n2 =
2 x 22 = 8 electrons
M shell = 2n2 =
2 x 32 = 18 electrons
In the N shell, the balance is four electrons, which are even in number.
Atomic Structure of Elements:
|
Atomic |
Element |
Proton |
Electrons per level |
||||||
|
K |
L |
M |
N |
O |
P |
Q |
|||
|
1 |
Hydrogen (H) |
1 |
1 |
||||||
|
2 |
Helium (He) |
2 |
2 |
||||||
|
3 |
Lithium (Li) |
3 |
2 |
1 |
|||||
|
5 |
Boron (B) |
5 |
2 |
3 |
|||||
|
6 |
Carbon (C) |
6 |
2 |
4 |
|||||
|
7 |
Nitrogen (N) |
7 |
2 |
5 |
|||||
|
8 |
Oxygen (O) |
8 |
2 |
6 |
|||||
|
10 |
Neon (Ne) |
10 |
2 |
8 |
|||||
|
11 |
Sodium (Na) |
11 |
2 |
8 |
1 |
||||
|
12 |
Magnesium (Mg) |
12 |
2 |
8 |
2 |
||||
|
13 |
Aluminium (Al) |
13 |
2 |
8 |
3 |
||||
|
14 |
Silicon (Si) |
14 |
2 |
8 |
4 |
||||
|
15 |
Phosphorous (P) |
15 |
2 |
8 |
5 |
||||
|
16 |
Sulphur (S) |
16 |
2 |
8 |
6 |
||||
|
17 |
Chlorine (Cl) |
17 |
2 |
8 |
7 |
||||
|
18 |
Argon (A) |
18 |
2 |
8 |
8 |
||||
|
19 |
Potassium (K) |
19 |
2 |
8 |
8 |
1 |
|||
|
24 |
Chromium (Cr) |
24 |
2 |
8 |
12 |
2 |
|||
|
26 |
Iron (Fe) |
26 |
2 |
8 |
14 |
2 |
|||
|
27 |
Cobalt (Co) |
27 |
2 |
8 |
14 |
3 |
|||
|
28 |
Nickel (Ni) |
28 |
2 |
8 |
16 |
2 |
|||
|
29 |
Copper (Cu) |
29 |
2 |
8 |
18 |
1 |
|||
|
30 |
Zinc (Zn) |
30 |
2 |
8 |
18 |
2 |
|||
|
32 |
Germanium (Ge) |
32 |
2 |
8 |
18 |
4 |
|||
|
33 |
Arseni (As) |
33 |
2 |
8 |
18 |
5 |
|||
|
34 |
Selenium (Se) |
34 |
2 |
8 |
18 |
6 |
|||
|
36 |
Krypton (Kr) |
36 |
2 |
8 |
18 |
8 |
|||
|
47 |
Silver (Ag) |
47 |
2 |
8 |
18 |
18 |
1 |
||
|
48 |
Cadmium (Cd) |
48 |
2 |
8 |
18 |
18 |
2 |
||
|
50 |
Tin (Sn) |
50 |
2 |
8 |
18 |
18 |
4 |
||
|
51 |
Antimony (Sb) |
51 |
2 |
8 |
18 |
18 |
5 |
||
|
74 |
Tungsten (W) |
74 |
2 |
8 |
18 |
32 |
12 |
2 |
|
|
78 |
Platinum (Pt) |
78 |
2 |
8 |
18 |
32 |
16 |
2 |
|
|
79 |
Gold (Au) |
79 |
2 |
8 |
18 |
32 |
18 |
1 |
|
|
80 |
Mercury (Hg) |
80 |
2 |
8 |
18 |
32 |
18 |
2 |
|
|
82 |
Lead (Pb) |
82 |
2 |
8 |
18 |
32 |
18 |
4 |
|