Period (periodic table)

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Period periodic table
Periods in periodic table | Image: Learnool

A period in the periodic table is a horizontal row of elements that share the same number of electron shells. In total, there are seven periods in the periodic table, each containing a different number of elements. The number of elements in a period corresponds to the number of electrons that can occupy the electron shells of atoms in that period.

The first period of the periodic table contains only two elements, hydrogen and helium. These two elements have only one electron shell and are therefore classified as belonging to the first period. The second period contains eight elements, from lithium to neon, which have two electron shells. Each subsequent period contains one additional electron shell, with the seventh period containing the elements with the largest electron shells known to date.

Elements within a period exhibit periodic trends in their properties, including decreasing atomic radius and increasing ionization energy and electronegativity from left to right. The elements within a period also exhibit similar chemical properties due to the number of valence electrons in their outermost electron shell.

The concept of periods in the periodic table was first proposed by Russian chemist Dmitri Mendeleev in the late 1800s. By arranging the elements in order of increasing atomic number and placing elements with similar properties in the same column, Mendeleev created a comprehensive system that allowed for the prediction of undiscovered elements and their properties. The periodic table has since become one of the most fundamental and useful tools in chemistry, providing insight into the behavior and properties of the elements.

On periodic table

group 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
period
1 1
H
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Hydrogen
2
He
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Helium
2 3
Li
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Lithium
4
Be
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Beryllium
5
B
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Boron
6
C
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Carbon
7
N
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Nitrogen
8
O
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Oxygen
9
F
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Fluorine
10
Ne
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Neon
3 11
Na
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Sodium
12
Mg
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Magnesium
13
Al
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Aluminium
14
Si
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Silicon
15
P
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Phosphorus
16
S
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Sulfur
17
Cl
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Chlorine
18
Ar
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Argon
4 19
K
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Potassium
20
Ca
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Calcium
21
Sc
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Scandium
22
Ti
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Titanium
23
V
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Vanadium
24
Cr
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Chromium
25
Mn
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Manganese
26
Fe
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Iron
27
Co
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Cobalt
28
Ni
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Nickel
29
Cu
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Copper
30
Zn
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Zinc
31
Ga
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Gallium
32
Ge
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Germanium
33
As
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Arsenic
34
Se
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Selenium
35
Br
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Bromine
36
Kr
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Krypton
5 37
Rb
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Rubidium
38
Sr
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Strontium
39
Y
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Yttrium
40
Zr
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Zirconium
41
Nb
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Niobium
42
Mo
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Molybdenum
43
Tc
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Technetium
44
Ru
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Ruthenium
45
Rh
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Rhodium
46
Pd
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Palladium
47
Ag
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Silver
48
Cd
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Cadmium
49
In
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Indium
50
Sn
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Tin
51
Sb
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Antimony
52
Te
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Tellurium
53
I
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Iodine
54
Xe
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Xenon
6 55
Cs
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Caesium
56
Ba
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Barium
72
Hf
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Hafnium
73
Ta
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Tantalum
74
W
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Tungsten
75
Re
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Rhenium
76
Os
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Osmium
77
Ir
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Iridium
78
Pt
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Platinum
79
Au
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Gold
80
Hg
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Mercury
81
Tl
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Thallium
82
Pb
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Lead
83
Bi
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Bismuth
84
Po
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Polonium
85
At
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Astatine
86
Rn
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Radon
7 87
Fr
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Francium
88
Ra
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Radium
104
Rf
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Rutherfordium
105
Db
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Dubnium
106
Sg
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Seaborgium
107
Bh
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Bohrium
108
Hs
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Hassium
109
Mt
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Meitnerium
110
Ds
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Darmstadtium
111
Rg
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Roentgenium
112
Cn
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Copernicium
113
Nh
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Nihonium
114
Fl
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Flerovium
115
Mc
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Moscovium
116
Lv
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Livermorium
117
Ts
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Tennessine
118
Og
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Oganesson
57
La
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Lanthanum
58
Ce
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Cerium
59
Pr
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Praseodymium
60
Nd
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Neodymium
61
Pm
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Promethium
62
Sm
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Samarium
63
Eu
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Europium
64
Gd
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Gadolinium
65
Tb
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Terbium
66
Dy
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Dysprosium
67
Ho
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Holmium
68
Er
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Erbium
69
Tm
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Thulium
70
Yb
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Ytterbium
71
Lu
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Lutetium
89
Ac
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Actinium
90
Th
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Thorium
91
Pa
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Protactinium
92
U
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Uranium
93
Np
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Neptunium
94
Pu
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Plutonium
95
Am
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Americium
96
Cm
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Curium
97
Bk
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Berkelium
98
Cf
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Californium
99
Es
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Einsteinium
100
Fm
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Fermium
101
Md
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Mendelevium
102
No
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Nobelium
103
Lr
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Lawrencium
period
1 – period 1 element 5 – period 5 element
2 – period 2 element 6 – period 6 element
3 – period 3 element 7 – period 7 element
4 – period 4 element

From top to bottom, the periodic table consists of 7 periods, with each period containing a different number of elements: period 1 has 2 elements, period 2 and period 3 have 8 elements each, period 4 and period 5 have 18 elements each, and period 6 and period 7 have 32 elements each, which makes a total of 118 known elements.

Period 1

Period 1 element | Image: Learnool

Period 1 is the first row of elements in the periodic table, consisting of only two elements, hydrogen (H) and helium (He).

Hydrogen

Hydrogen is the lightest and most abundant element in the universe, and also the most abundant element in the Earth’s crust. It is highly reactive and can form covalent, ionic, or metallic bonds with other elements. Hydrogen gas is used in various industrial processes, such as in the production of ammonia and methanol. It is also used as a fuel for rockets and in fuel cells for generating electricity.

Helium

Helium is an inert gas and is the second lightest element after hydrogen. It is the most stable of all the noble gases, and is the second most abundant element in the universe. Helium gas is used in various applications, such as in cooling systems for MRI machines and nuclear reactors, in airships and balloons, and as a shielding gas in welding processes.

Period 2

Period 2 element | Image: Learnool

Period 2 of the periodic table contains eight elements, namely lithium, beryllium, boron, carbon, nitrogen, oxygen, fluorine, and neon.

Lithium

Lithium (Li) is a soft, silvery-white metal that belongs to the alkali metal group. It is highly reactive and has the lowest density of all metals. Lithium is commonly used in batteries, ceramics, and as a mood stabilizer in psychiatric medicine.

Beryllium

Beryllium (Be) is a hard, grayish metal that belongs to the alkaline earth metals. It has a high melting point and is used in nuclear reactors, aerospace applications, and X-ray equipment.

Boron

Boron (B) is a metalloid that has a high melting point and low density. It is used in a variety of applications, such as in ceramics, glass, and detergents.

Carbon

Carbon (C) is a nonmetallic element that is essential for life. It exists in several allotropes, including graphite and diamond. Carbon is used in a wide range of applications, such as in the production of steel and as a fuel source.

Nitrogen

Nitrogen (N) is a colorless, odorless gas that makes up about 78% of Earth’s atmosphere. It is an essential element for life and is used in the production of ammonia, which is used in fertilizers.

Oxygen

Oxygen (O) is a colorless, odorless gas that makes up about 21% of Earth’s atmosphere. It is essential for respiration and is used in a variety of applications, such as in steel production and medical oxygen tanks.

Fluorine

Fluorine (F) is a highly reactive, pale yellow gas that belongs to the halogen group. It is used in the production of uranium, as a refrigerant, and in the manufacture of high-performance plastics.

Neon

Neon (Ne) is a colorless, odorless gas that belongs to the noble gas group. It is used in neon lights, high-voltage indicators, and television tubes.

Period 3

Period 3 element | Image: Learnool

Period 3 refers to the third row of elements in the periodic table, consisting of sodium, magnesium, aluminum, silicon, phosphorus, sulfur, chlorine, and argon.

Sodium

Sodium (Na) is a soft, silvery-white, highly reactive metal. It is an essential element for animal life and is used in various applications, including the production of soap and as a coolant in nuclear reactors.

Magnesium

Magnesium (Mg) is a shiny gray metal that is widely used in alloys, medicine, and pyrotechnics. It is also an essential element for plants and animals, and is found in many foods such as nuts, seeds, and green leafy vegetables.

Aluminum

Aluminum (Al) is a lightweight, silvery-white metal that is widely used in various applications, including packaging, transportation, construction, and electrical systems. It is the most abundant metal in the Earth’s crust and is highly resistant to corrosion.

Silicon

Silicon (Si) is a metalloid that is widely used in the production of semiconductors, solar cells, and computer chips. It is the second most abundant element in the Earth’s crust and is also found in various minerals and rocks.

Phosphorus

Phosphorus (P) is a highly reactive, non-metallic element that is essential for life. It is found in DNA and is used in various applications, including fertilizers, detergents, and flame retardants.

Sulfur

Sulfur (S) is a non-metallic element that is found in various forms in the Earth’s crust. It is used in various applications, including the production of fertilizers, chemicals, and pharmaceuticals.

Chlorine

Chlorine (Cl) is a highly reactive, greenish-yellow gas that is used in various applications, including the production of bleach and disinfectants. It is also an essential element for life and is found in various compounds such as salt.

Argon

Argon (Ar) is an inert, colorless, odorless gas that is the third most abundant gas in the Earth’s atmosphere. It is used in various applications, including welding, lighting, and as a protective gas in various industrial processes.

Period 4

Period 4 element | Image: Learnool

Period 4 of the periodic table includes eighteen elements, ranging from potassium (K) to krypton (Kr). These elements share some common characteristics due to their placement in the same period.

The first half of the period consists of elements that have a filling 3d subshell, such as scandium (Sc), titanium (Ti), and iron (Fe). These elements are known for their transition metal properties, such as high melting and boiling points, malleability, and good electrical conductivity. They are also commonly used in various industries, such as construction, aerospace, and electronics.

The second half of the period consists of elements that have a filling 4p subshell, such as germanium (Ge), selenium (Se), and bromine (Br). These elements exhibit more non-metallic properties, such as lower melting and boiling points, and increased electronegativity. They are commonly used in semiconductors, solar cells, and pharmaceuticals. The noble gas, krypton (Kr) is the last element in period 4 and is known for its inertness and use in lighting.

Period 5

Period 5 element | Image: Learnool

Period 5 of the periodic table contains 18 elements, beginning with the alkali metal rubidium (Rb) and ending with the noble gas xenon (Xe). Elements in period 5 generally have larger atomic radii and lower ionization energies compared to the elements in period 4, although their electron affinities are generally lower due to the trend of decreasing electron affinity down a group. This is due to the fact that the valence electrons in period 5 are in higher energy levels, farther away from the nucleus, and thus experience less attraction from the positively charged nucleus.

One notable characteristic of period 5 elements is their diverse range of chemical properties. For example, the transition metals in period 5, such as molybdenum (Mo) and technetium (Tc), have high melting and boiling points, and are often used as catalysts. On the other hand, iodine (I) is a highly reactive nonmetal belonging to the halogen group, while xenon (Xe) is an inert noble gas with very low reactivity.

Period 6

Period 6 element | Image: Learnool

Period 6 of the periodic table contains 32 elements, starting with cesium (Cs) and ending with radon (Rn). This period includes some important elements such as barium (Ba), hafnium (Hf), tungsten (W), platinum (Pt), and gold (Au). These elements have important uses in industry, such as hafnium in nuclear reactors and tungsten in the manufacturing of high-temperature alloys. Others, such as gold and platinum, are highly valued for their beauty and rarity.

Period 7

Period 7 element | Image: Learnool

Period 7 of the periodic table contains 32 elements, starting with francium (Fr) and ending with oganesson (Og). The elements in this period have progressively increasing atomic numbers and are known for their unique chemical properties. Many of the elements in period 7 are synthetic and highly unstable, with short half-lives, making their study challenging. Elements such as uranium (U) and plutonium (Pu) are important in nuclear energy and have been the subject of extensive research. On the other hand, elements like francium (Fr) and oganesson (Og) are highly reactive and have limited practical applications.

Period 8

Period 8 elements are yet to be discovered, and therefore, their properties and characteristics are still unknown. The theoretical predictions suggest that the eighth period would consist of 18 elements, and their electronic configurations would be similar to the seventh period elements, with 5g orbitals filling up. Theoretical calculations also suggest that the elements of the eighth period would be extremely unstable and radioactive, and their lifetimes would be incredibly short.

The search for the elements of the eighth period is still ongoing, and scientists are actively working to synthesize these elements in laboratories using advanced technologies. However, due to the expected instability of these elements, it remains to be seen whether the predicted elements of the eighth period are physically possible. Until then, the properties and characteristics of the eighth period elements remain a mystery, and the possibility of the ninth period is still uncertain.

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Learnool.com was founded by Deep Rana, who is a mechanical engineer by profession and a blogger by passion. He has a good conceptual knowledge on different educational topics and he provides the same on this website. He loves to learn something new everyday and believes that the best utilization of free time is developing a new skill.

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