Chemistry
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Electron arrangement
- Write the electron arrangement of atoms belonging to periods 1 to 3
- Write the electron arrangement of atoms belonging to periods 4 to 7
- Electron arrangement list
- Write the electronic arrangement of a monoatomic ion in steady state
- Electron arrangement list of ions of the first three periods
Write the electron arrangement of atoms belonging to periods 1 to 3
The electronic arrangement describes the distribution of the electrons in the different shells, it is written respecting the following rules:
• Each shell occupied by electrons is noted using its letter K, L, M etc.
• The occupied shells are indicated in the kernel remoteness order (which is also an alphabetical order).
• Each shell is noted in parenthesis with the number of electrons in superscript (sometimes parentheses are omitted).
Generally, to determine the electronic arrangement of an atom we proceed as follows:
• Find the number of electrons of the atom (the periodic table atoms gives it atomic numbers which is equal to the number of electrons)
• These electrons are distributed in shells according to a simple rule, they first occupy the lowest shells and they are placed first in the shell K. If it has a single electron it is noted (K)1 and if it is full it is noted (K)2.
• If the atom has more than two electrons then the following electrons occupy the shell L noted (L) with at most 8 electrons.
• If the atom has more than 10 electrons (2 + 8) then the remaining electrons are placed in the M shell… until all electrons are associated with a shell
Example 1: the boron atom
Its atomic number Z = 5 so it has 5 electronsThe first two electrons occupy the shell K which is noted (K) 2
There then remain 3 electrons, which occupy the L layer, are noted (L) 3
The electronic arrangement of the boron atom is therefore: (K) 2 (L) 3
Note: its outer layer is L.
Example 2: the sulfur atom
Its atomic number is Z = 16 so it has 16 electronsThe first two electrons are on the layer K noted (K) 2
There are 14 left, so the next 8 are on the L layer noted (L) 8
There remain 6 electrons on the layer M noted (M) 6
Therefore, we obtain an electronic structure (electronic configuration) which is noted (K) 2 (L) 8 (M) 6
Note: its outermost shell is M.
Write the electron arrangement of atoms belonging to periods 4 to 7
The filling of these shells follows the same rule as the periods (lines) 1 to 3 of the periodic table. Electrons occupy first time the lowest energy levels in priority.
However,
from the fourth period it is necessary to consider another
particularity of the electronic shells:
they are subdivided into sub-shells
each one having its own energy level. If one of the sub-shells
has an energy higher than one of the sub-shells
of the upper shell
therefore the filling is not necessarily made by the lowest shells
to the highest shells.
It becomes more relevant to describe the electronic distribution by
writing the electronic configuration
(which details the distribution on the sub-shells).
Electron arrangement list
|
Atom |
Z |
Electronic Structure ( electron configuration) |
|
Hydrogen |
1 |
(K)1 |
|
Helium |
2 |
(K)2 |
|
Lithium |
3 |
(K)2(L)1 |
|
Beryllium |
4 |
(K)2(L)2 |
|
Bore |
5 |
(K)2(L)3 |
|
Carbon |
6 |
(K)2(L)4 |
|
Azote |
7 |
(K)2(L)5 |
|
Oxygen |
8 |
(K)2(L)6 |
|
Fluor |
9 |
(K)2(L)7 |
|
Neon |
10 |
(K)2(L)8 |
|
Sodium |
11 |
(K)2(L)8 (M)1 |
|
Magnesium |
12 |
(K)2(L)8 (M)2 |
|
Aluminum |
13 |
(K)2(L)8 (M)3 |
|
Silicon |
14 |
(K)2(L)8 (M)4 |
|
Phosphor |
15 |
(K)2(L)8 (M)5 |
|
Sulfur |
16 |
(K)2(L)8 (M)6 |
|
Chlorine |
17 |
(K)2(L)8 (M)7 |
|
Argon |
18 |
(K)2(L)8 (M)8 |
|
Potassium |
19 |
(K)2(L)8 (M)8(N)1 |
|
Calcium |
20 |
(K)2(L)8 (M)8(N)2 |
|
Scandium |
21 |
(K)2(L)8 (M)9(N)2 |
|
Titanium |
22 |
(K)2(L)8 (M)10(N)2 |
|
Vanadium |
23 |
(K)2(L)8 (M)11(N)2 |
|
Chrome |
24 |
(K)2(L)8 (M)13(N)1 |
|
Manganese |
25 |
(K)2(L)8 (M)13(N)2 |
|
Iron |
26 |
(K)2(L)8 (M)14(N)2 |
|
Cobalt |
27 |
(K)2(L)8 (M)15(N)2 |
|
Nickel |
28 |
(K)2(L)8 (M)16(N)2 |
|
Copper |
29 |
(K)2(L)8 (M)18(N)1 |
|
Zinc |
30 |
(K)2(L)8 (M)18(N)2 |
|
Gallium |
31 |
(K)2(L)8 (M)18(N)3 |
|
Germanium |
32 |
(K)2(L)8 (M)18(N)4 |
|
Arsenic |
33 |
(K)2(L)8 (M)18(N)5 |
|
Selenium |
34 |
(K)2(L)8 (M)18(N)6 |
|
Brome |
35 |
(K)2(L)8 (M)18(N)7 |
|
Krypton |
36 |
(K)2(L)8 (M)18(N)8 |
|
Rubidium |
37 |
(K)2(L)8 (M)18(N)8(O)1 |
|
Strontium |
38 |
(K)2(L)8 (M)18(N)8(O)2 |
|
Yttrium |
39 |
(K)2(L)8 (M)18(N)9(O)2 |
|
Zirconium |
40 |
(K)2(L)8 (M)18(N)10(O)2 |
|
Niobium |
41 |
(K)2(L)8 (M)18(N)12(O)1 |
|
Molybdenum |
42 |
(K)2(L)8 (M)18(N)13(O)1 |
|
Technetium |
43 |
(K)2(L)8 (M)18(N)13(O)2 |
|
Ruthenium |
44 |
(K)2(L)8 (M)18(N)15(O)1 |
|
Rhodium |
45 |
(K)2(L)8 (M)18(N)16(O)1 |
|
Palladium |
46 |
(K)2(L)8 (M)18(N)18 |
|
Silver |
47 |
(K)2(L)8 (M)18(N)18(O)1 |
|
Cadmium |
48 |
(K)2(L)8 (M)18(N)18(O)2 |
|
Indium |
49 |
(K)2(L)8 (M)18(N)18(O)3 |
|
Pewter |
50 |
(K)2(L)8 (M)18(N)18(O)4 |
|
Antimony |
51 |
(K)2(L)8 (M)18(N)18(O)5 |
|
Tellurium |
52 |
(K)2(L)8 (M)18(N)18(O)6 |
|
Iodine |
53 |
(K)2(L)8 (M)18(N)18(O)7 |
|
Xenon |
54 |
(K)2(L)8 (M)18(N)18(O)8 |
|
Cesium |
55 |
(K)2(L)8 (M)18(N)18(O)8(P)1 |
|
Barium |
56 |
(K)2(L)8 (M)18(N)18(O)8(P)2 |
|
Lanthanum |
57 |
(K)2(L)8 (M)18(N)18(O)9(P)2 |
|
Cerium |
58 |
(K)2(L)8 (M)18(N)19(O)9(P)2 |
|
Praseodymium |
59 |
(K)2(L)8 (M)18(N)21(O)8(P)2 |
|
Neodymium |
60 |
(K)2(L)8 (M)18(N)22(O)8(P)2 |
|
Promethium |
61 |
(K)2(L)8 (M)18(N)23(O)8(P)2 |
|
Samarium |
62 |
(K)2(L)8 (M)18(N)24(O)8(P)2 |
|
Europium |
63 |
(K)2(L)8 (M)18(N)25(O)8(P)2 |
|
Gadolinium |
64 |
(K)2(L)8 (M)18(N)25(O)9(P)2 |
|
Terbium |
65 |
(K)2(L)8 (M)18(N)27(O)8(P)2 |
|
Dysprosium |
66 |
(K)2(L)8 (M)18(N)28(O)8(P)2 |
|
Holmium |
67 |
(K)2(L)8 (M)18(N)29(O)8(P)2 |
|
Erbium |
68 |
(K)2(L)8 (M)18(N)30(O)8(P)2 |
|
Thulium |
69 |
(K)2(L)8 (M)18(N)31(O)8(P)2 |
|
Ytterbium |
70 |
(K)2(L)8 (M)18(N)32(O)8(P)2 |
|
Lutetium |
71 |
(K)2(L)8 (M)18(N)32(O)9(P)2 |
|
Hafnium |
72 |
(K)2(L)8 (M)18(N)32(O)10(P)2 |
|
Tantalum |
73 |
(K)2(L)8 (M)18(N)32(O)11(P)2 |
|
Tungsten |
74 |
(K)2(L)8 (M)18(N)32(O)12(P)2 |
|
Rhenium |
75 |
(K)2(L)8 (M)18(N)32(O)13(P)2 |
|
Osmium |
76 |
(K)2(L)8 (M)18(N)32(O)14(P)2 |
|
Iridium |
77 |
(K)2(L)8 (M)18(N)32(O)15(P)2 |
|
Platine |
78 |
(K)2(L)8 (M)18(N)32(O)17(P)1 |
|
Gold |
79 |
(K)2(L)8 (M)18(N)32(O)18(P)1 |
|
Mercury |
80 |
(K)2(L)8 (M)18(N)32(O)18(P)2 |
|
Thallium |
81 |
(K)2(L)8 (M)18(N)32(O)18(P)3 |
|
Plumb |
82 |
(K)2(L)8 (M)18(N)32(O)18(P)4 |
|
Bismuth |
83 |
(K)2(L)8 (M)18(N)32(O)18(P)5 |
|
Polonium |
84 |
(K)2(L)8 (M)18(N)32(O)18(P)6 |
|
Astatine |
85 |
(K)2(L)8 (M)18(N)32(O)18(P)7 |
|
Radon |
86 |
(K)2(L)8 (M)18(N)32(O)18(P)8 |
|
Francium |
87 |
(K)2(L)8 (M)18(N)32(O)18(P)8(Q)1 |
|
Radium |
88 |
(K)2(L)8 (M)18(N)32(O)18(P)8(Q)2 |
|
Actinium |
89 |
(K)2(L)8 (M)18(N)32(O)18(P)9(Q)2 |
|
Thorium |
90 |
(K)2(L)8 (M)18(N)32(O)18(P)10(Q)2 |
|
Protactinium |
91 |
(K)2(L)8 (M)18(N)32(O)20(P)9(Q)2 |
|
Uranium |
92 |
(K)2(L)8 (M)18(N)32(O)21(P)9(Q)2 |
|
Neptunium |
93 |
(K)2(L)8 (M)18(N)32(O)22(P)9(Q)2 |
|
Plutonium |
94 |
(K)2(L)8 (M)18(N)32(O)24(P)8(Q)2 |
|
Americium |
95 |
(K)2(L)8 (M)18(N)32(O)25(P)8(Q)2 |
|
Curium |
96 |
(K)2(L)8 (M)18(N)32(O)25(P)9(Q)2 |
|
Berkelium |
97 |
(K)2(L)8 (M)18(N)32(O)27(P)8(Q)2 |
|
Californium |
98 |
(K)2(L)8 (M)18(N)32(O)28(P)8(Q)2 |
|
Einsteinium |
99 |
(K)2(L)8 (M)18(N)32(O)29(P)8(Q)2 |
|
Fermium |
100 |
(K)2(L)8 (M)18(N)32(O)30(P)8(Q)2 |
|
Mendelevium |
101 |
(K)2(L)8 (M)18(N)32(O)31(P)8(Q)2 |
|
Nobelium |
102 |
(K)2(L)8 (M)18(N)32(O)32(P)8(Q)2 |
|
Lawrencium |
103 |
(K)2(L)8 (M)18(N)32(O)32(P)8(Q)3 |
|
Rutherfordium |
104 |
(K)2(L)8 (M)18(N)32(O)32(P)10(Q)2 |
|
Dubnium |
105 |
(K)2(L)8 (M)18(N)32(O)32(P)11(Q)2 |
|
Seaborgium |
106 |
(K)2(L)8 (M)18(N)32(O)32(P)12(Q)2 |
|
Bohrium |
107 |
(K)2(L)8 (M)18(N)32(O)32(P)13(Q)2 |
|
Hassium |
108 |
(K)2(L)8 (M)18(N)32(O)32(P)14(Q)2 |
|
Meitnerium |
109 |
(K)2(L)8 (M)18(N)32(O)32(P)15(Q)2 |
|
Darmstadtium |
110 |
(K)2(L)8 (M)18(N)32(O)32(P)16(Q)2 |
|
Roentgenium |
111 |
(K)2(L)8 (M)18(N)32(O)32(P)17(Q)2 |
|
Copernicium |
112 |
(K)2(L)8 (M)18(N)32(O)32(P)18(Q)2 |
|
Nihonium |
113 |
(K)2(L)8 (M)18(N)32(O)32(P)18(Q)3 |
|
Flerovium |
114 |
(K)2(L)8 (M)18(N)32(O)32(P)18(Q)4 |
|
Moscovium |
115 |
(K)2(L)8 (M)18(N)32(O)32(P)18(Q)5 |
|
Livermorium |
116 |
(K)2(L)8 (M)18(N)32(O)32(P)18(Q)6 |
|
Tennessine |
117 |
(K)2(L)8 (M)18(N)32(O)32(P)18(Q)7 |
|
Oganesson |
118 |
(K)2(L)8 (M)18(N)32(O)32(P)18(Q)8 |
Write the electronic arrangement of a monoatomic ion in steady state
By definition, a monoatomic ion is a chemical species having either an electron defect compared to the atom (in this case it is a positively charged cation) or an excess of electrons (in this case it is an anion negatively charged).
To write the electronic arrangement of an ion, it is sufficient to determine the number of electrons it owns:
• Find the atomic number of the corresponding element in the periodic table which corresponds to the number of electrons of the atomic form.
• Use the chemical formula to determine the electron difference to the atomic shape. An ion with a single positive charge has one less electron than the atom, an ion with two positive charges has two fewer electrons, one ion carrying a negative charge has an extra electron relative to the atom shape, an ion with two negative charges has two less electrons etc.
• Then apply the same method to determine the electronic arrangement of an atom.
Note: Stable ions for each element can be predicted by the duet and octet rule.
Example 1, sodium ion Na +
- The sodium has as an atomic number Z = 11 therefore the sodium atom has 11 electrons
- The sodium ion carries a positive charge so it has one electron less than the atom, 11-1 = 10 electrons.
- The first two electrons occupy the K shell
- The next eight are on the L layer
- The electronic arrangement of the sodium ion is therefore (K)2(L)8
Example 2, the sulfide ion S2-
The element sulfur has for atomic number Z = 16 therefore the sulfur atom has 16 electronsThe sulfide ion has two negative charges so it has two more electrons than the atom, 16 + 2 = 18 electrons.
The first two electrons occupy the K shell
The next eight are on the L shell
The last 8 are on the shell M
Therefore, the electronic structure of the sodium ion is (K)2(L)8 (M)8
Electron arrangement list of ions of the first three periods
Note: some of these ions (hydride, silicon, phosphide ...) do not exist in aqueous solution (they are not stable) but may be present in ionic solid.
