Periodic Table of Elements

Periodic table elements arrangement in chemistry in order of increasing atomic number or the full number of protons in the atomic nucleus is named as modern law of the periodic table. According to the modern law or long form of the periodic table, the list of chemical elements along groups or periods is organized on the basis of electronic configuration and classified into four categories s, p, d, and f-block elements. The modern law for the periodic table of elements suggests that the physical and chemical properties of elements are the periodic functions of the atomic number. The modern law of the periodic table comes due to the breakdown of Mendeleev’s (1861) scientific classification based on atomic weight or masses of the chemical elements. The names, symbols, atomic numbers, and electronic configuration of 118 periodic table elements are given below in the picture:

Periodic table chemical elements names, symbol, atomic numbers, and properties

Modern Periodic Table

The modern law for the periodic table of elements comes to remove the defects of Mendeleev Mendeleev’s scientific classification. In the modern periodic table chart, the elements are represented by two parts, vertical columns (group) and horizontal rows (period) in chemistry or chemical science

The initial discovery was explained by Dmitri Ivanovich Mendeleev in 1861 and Mosely in 1911. However, the Bohr model or scheme suggested the scientific development of groups and periods of the periodic table elements.

Periods in Periodic Table of Elements

The periods on the periodic table are the horizontal rows used to arrange the chemical elements. The long form or modern form of the periodic table contains seven (7) periods for the accommodation of elements.

First Period

The principal quantum number (n) = 1 indicates that there is only one main energy level for the elements in this period. Therefore, this period has two chemical elements beginning with hydrogen and ending with inert gas helium.

Second Period

There are two sub-shells (2s and 2p) for the elements in this period. Therefore, this period has (2×1 + 3×2) = 8 chemical elements beginning with the alkali metal lithium and ending with the inert gas neon.

Third Period

There are two sub-shells (3s and 3p) for the elements in this period. Therefore, this period has (2×1 + 3×2) = 8 chemical elements beginning with another alkali metal sodium ending with the inert gas argon.

Fourth Period

There are three sub-shells (4s, 4p, and 3d) for the elements in this period. Therefore, this period has (2×1 + 3×2 + 5×2) = 18 chemical elements beginning with an alkali metal potassium and ending with an inert gas krypton.

Fifth Period

There are also three sub-shells (5s, 5p, and 4d) for the elements in this period. Therefore, this period has (2×1 + 3×2 + 5×2) = 18 chemical elements beginning with the alkali metal rubidium and ending with inert gas xenon. It contains eight typical elements and ten transition metals.

Sixth Period

There are four sub-shells (6s, 6p, 5d, and 4f) for the elements in this period. Therefore, this period has (2×1 + 3×2 + 5×2 + 7×2) = 32 chemical elements beginning with the alkali metal cesium and ending with an inert gas radon.

The sixth period contains eight typical elements, ten transition metals, and fourteen lanthanides or rare earth elements. The lanthanides (lanthanum to ytterbium) are placed in the lower position of the periodic table.

Seventh Period

There are also four sub-shells (7s, 7p, 6d, and 5f) for the elements in this period. Therefore, this period has (2×1 + 3×2 + 5×2 + 7×2) = 32 chemical elements beginning with the radioactive francium and ending with oganesson.

Most of the elements in this period are radioactive. The actinides (actinium to nobelium) are placed in the lower position of the periodic table.

Groups in Periodic Table of Elements

The vertical columns are called groups for periodic table elements. The modern or long form of the periodic table contains eighteen (18) groups where chemical elements are arranged.

  • Groups 1 and 2, and groups 13 to 17 contain the typical chemical elements of the period table. All the elements of a particular group of normal elements have the same number of valence shell electrons in their outer quantum shell.
  • Group 3 to Group 12 elements are called transition metals.
  • Group 18 contains inert gases starting with helium and ending with oganesson.

In the modern periodic table, the elements on the left side are metals and the right side are nonmetals. The transition elements are placed between the metals and nonmetals of the periodic table.

Periodic Table of Elements List

The list of chemical elements arranged in groups and periods of the periodic table are listed below in the table,

Group 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Period 1 Hydro­gen1H1.008 He­lium2He4.0026
2 Lith­ium3Li6.94 Beryl­lium4Be9.0122 Boron5B10.81 Carbon6C12.011 Nitro­gen7N14.007 Oxy­gen8O15.999 Fluor­ine9F18.998 Neon10Ne20.180
3 So­dium11Na22.990 Magne­sium12Mg24.305 Alumin­ium13Al26.982 Sili­con14Si28.085 Phos­phorus15P30.974 Sulfur16S32.06 Chlor­ine17Cl35.45 Argon18Ar39.95
4 Potas­sium19K39.098 Cal­cium20Ca40.078 Scan­dium21Sc44.956 Tita­nium22Ti47.867 Vana­dium23V50.942 Chrom­ium24Cr51.996 Manga­nese25Mn54.938 Iron26Fe55.845 Cobalt27Co58.933 Nickel28Ni58.693 Copper29Cu63.546 Zinc30Zn65.38 Gallium31Ga69.723 Germa­nium32Ge72.630 Arsenic33As74.922 Sele­nium34Se78.971 Bromine35Br79.904 Kryp­ton36Kr83.798
5 Rubid­ium37Rb85.468 Stront­ium38Sr87.62 Yttrium39Y88.906 Zirco­nium40Zr91.224 Nio­bium41Nb92.906 Molyb­denum42Mo95.95 Tech­netium43Tc[97] Ruthe­nium44Ru101.07 Rho­dium45Rh102.91 Pallad­ium46Pd106.42 Silver47Ag107.87 Cad­mium48Cd112.41 Indium49In114.82 Tin50Sn118.71 Anti­mony51Sb121.76 Tellur­ium52Te127.60 Iodine53I126.90 Xenon54Xe131.29
6 Cae­sium55Cs132.91 Ba­rium56Ba137.33 Lan­thanum57La138.91 Haf­nium72Hf178.49 Tanta­lum73Ta180.95 Tung­sten74W183.84 Rhe­nium75Re186.21 Os­mium76Os190.23 Iridium77Ir192.22 Plat­inum78Pt195.08 Gold79Au196.97 Mer­cury80Hg200.59 Thallium81Tl204.38 Lead82Pb207.2 Bis­muth83Bi208.98 Polo­nium84Po[209] Asta­tine85At[210] Radon86Rn[222]
7 Fran­cium87Fr[223] Ra­dium88Ra[226] Actin­ium89Ac[227] Ruther­fordium104Rf[267] Dub­nium105Db[268] Sea­borgium106Sg[269] Bohr­ium107Bh[270] Has­sium108Hs[269] Meit­nerium109Mt[278] Darm­stadtium110Ds[281] Roent­genium111Rg[282] Coper­nicium112Cn[285] Nihon­ium113Nh[286] Flerov­ium114Fl[289] Moscov­ium115Mc[290] Liver­morium116Lv[293] Tenness­ine117Ts[294] Oga­nesson118Og[294]
Lan­thanum57La138.91 Cerium58Ce140.12 Praseo­dymium59Pr140.91 Neo­dymium60Nd144.24 Prome­thium61Pm[145] Sama­rium62Sm150.36 Europ­ium63Eu151.96 Gadolin­ium64Gd157.25 Ter­bium65Tb158.93 Dyspro­sium66Dy162.50 Hol­mium67Ho164.93 Erbium68Er167.26 Thulium69Tm168.93 Ytter­bium70Yb173.05 Lute­tium71Lu174.97
Actin­ium89Ac[227] Thor­ium90Th232.04 Protac­tinium91Pa231.04 Ura­nium92U238.03 Neptu­nium93Np[237] Pluto­nium94Pu[244] Ameri­cium95Am[243] Curium96Cm[247] Berkel­ium97Bk[247] Califor­nium98Cf[251] Einstei­nium99Es[252] Fer­mium100Fm[257] Mende­levium101Md[258] Nobel­ium102No[259] Lawren­cium103Lr[266]

Long Form of Periodic Table

According to the above definition and explanation, the long form of the periodic table elements has three units left, right, and middle sections for learning chemistry or physics in science.

  • Left Portion: The left section or portion in the table contains Group 1 (alkali metals) and Group 2 (alkaline earth metals). These elements have extremely high electropositive character and very low ionization energy. Therefore, all these elements always show a positive oxidation number.
  • Right Portion: The right portion contains Group 13 to Group 18 elements. This portion of the table contains metals, metalloids, non-metals, and noble gases. Most of the nonmetals have high electron affinity. However, noble gases (helium, neon, argon, krypton, xenon, and radon) are non-reactive in nature.
  • Middle Portion: The organization of the middle portion (group 2 to group 12) of the periodic table elements made the relationship between the left and right sections. Therefore, the middle portion contains a list of transition metals or d-block and inner transition or f-block elements.

Blocks of Periodic Table Elements

The modern periodic law is based on the atomic number and valence shell electron arrangement of elements. In chemistry, according to the valence shell electron arrangement of elements, the different types of metals and non-metals are organized to form s, p, d, and f-block of the periodic table.

s-Block Elements

The names of s-block elements in the periodic table are given according to the arrangement of electrons. In the s-block, the valence electron enters into the ns-orbital and is filled progressively according to the configuration rules.

Group-1 (hydrogen, lithium, sodium, potassium, rubidium, cesium, and francium) and group-2 (beryllium, magnesium, calcium, strontium, barium, and radium) belong to s-block elements. The valence shell electron configuration of s-block elements is ns1→2. Here n = principle quantum number, or the number of periods.

p-Block Elements

P-block elements on the periodic table are organized by progressively filled p-orbital in valence shell electronic structure. However, helium is an exception with electron arrangement 1s2.

Group 13 to group 17 and noble gases (group 18) belong to p-block elements. Since the second period of p block elements (boron, carbon, nitrogen, oxygen, fluorine, and argon) have filled s-orbitals. Therefore, the valence shell electron configuration of such elements, 2s2 2p1→6, where n = number of periods.

d-Block and f-Block Elements

The name d-block (transition) or f-block (inner transition series) on the periodic table is given due to the presence of progressively filled d or f-orbitals in the valence shell electronic structure. The transition or inner transition family forms an ionic chemical bond with metals (s-block). Similarly, a covalent bond forms with non-metals (p-block).

3d-block elements scandium, titanium, vanadium, chromium, iron, cobalt, nickel, copper, and zinc are placed in the middle of the table. Therefore, they are between s and p-block with valence shell electronic configuration, 4s0→2 3d1-10.

The f-block elements on the periodic table are divided into two series, 4f or lanthanides and 5f or actinides. The f-block contains many missing elements discovered or synthesized by the nuclear reaction of radioactive isotopes.

Periodic Table Trends of Elements

Understanding the periodic table variation of ionization energy, electron affinity, electronegativity, acid-base properties, and oxidation number in redox reaction of chemical elements are very important characteristics for any discussion or information in chemistry or science. In learning chemistry, we summarize physical and chemical properties along the group and period.

Atomic Radii

The term atomic radii is generally used to derive the distance between the nucleus and the outermost shell of electrons.

On moving left to right in a period, the atomic radii of elements decrease because the number of protons or nuclear charge in the atom increses. However, the outermost electronic shell remains unchanged. When the nuclear charge in the same outermost electronic shell increses, the outer electrons are attached more strongly towards the nucleus.

On going down in a group, the atomic radii of elements increses due to the addition of new electrons to higher energy levels. It decreases electrostatic attraction between the nucleus and valence shell electrons.

Ionization Energy of Periodic Table Elements

Ionization energy (I or IE) is the amount of energy required to remove the most loosely bound electron or the outermost electron from an isolated gaseous atom of an element in its lowest energy state or ground state to produce a cation.

M (g) + Ionization energy → M+ + e−

The value of ionization energy generally increses in moving from left to right in a period because when we move from left to right nuclear change of the atoms of the elements also increses. The ionization ionization energy of 2nd-period elements increses in the following direction:

Be < Li < B < C < N < O < F < Ne

The exceptional first ionization energy trends for beryllium and nitrogen can be explained by a completely filled 2s orbital of the beryllium (1s22s2) atom and a half-filled 3p orbital of the nitrogen (1s22s22p3) atom.

On moving down top to bottom in a group the ionization energy generally decreases due to increased atomic radii of elements. Therefore, the lower member of crystalline solid metals like Ag, Au, Cd, and Hg has lower ionization energy.

The screening or shielding effect is also used to explain ionization energy variation of elements along a group of the periodic table. Therefore, in many cases, ionization energy from the top to bottom increases due to shielding electron or effective nuclear charges.

Electron Affinity of Elements in Periodic Table

Electron affinity (EA or E) is the amount of energy released when an electron is added to an isolated gaseous atom in its lowest energy state or ground state to produce an anion.

A (g) + e− → A− (g) + Electron affinity

  • When we move down a group, the electron affinity values generally decrease due to steady increses in the atomic radius of the elements. For example, ECl > EBr > EI.
  • Electron affinity values for elements generally increase on moving from left to right in a period of the periodic table.

The exception trend of electron affinity is also common for periodic table elements. For example, the electron affinity trend of the second-row elements is usually lower than the third-row.

Electronegativity of Elements in Periodic Table

The electronegativity of a bonded atom is defined as its relative tendency or ability to attract the shared electron pair towards itself.

  • The electronegativity increses on moving from left to right in a period.
  • Small atoms attract electrons more strongly than large ones. Therefore, when we move down in a group, the size and electropositive character of atoms increase.

The most electronegative periodic table elements are present in the top right-hand corner. However, the most electropositive elements are present in the bottom left-hand corner.

Oxidizing and Reducing Properties

When we move from left to right across a period in the periodic table, the oxidizing power of the elements generally increses, and the reducing power decreases.

When we go down in a group, the reducing power of elements increses while oxidizing power decreases. The fact is due size of the atom increses and ionisation energy decreases. Therefore, the reducing power of group 1 elements or alkali metals is in the following order:

Cs > Rb > K > Na > Li

Similarly, the oxidizing power of halogens decreases in the following order:

F > Cl > Br > I

Periodic Trends of Acid-base Character

Generally, when moving from left to right in a period the acidic character of the normal oxides of the elements goes to increses. The change from strongly basic character to strongly acidic character is due to an increase in the electronegativity value of the elements. The trends of acidic character for group 2 elements oxides are:

Na2O < MgO < Al2O3 < SiO2 < P4O10 < SO3 < Cl2O7

Metallic and Non-metallic Charcter

The periodic table elements having a higher value of electronegativity will be non-metals. However, a lower electronegativity will be a metal. Therefore, the metallic character in a period decreases from left to right. However, it can be increses from top to bottom in a group.

Periodic Table with Electron Configuration

The pair of elements are arranged diagonally to each other in the period table to describe simple relations or chemical properties like the electric polarization in chemistry. The diagonal pairs like beryllium and aluminum have a similar change/size ratio. Since the size increases to the lower period while the charge increases to the right. However, this rule can not work completely for all the periodic table elements.

Interesting facts in the periodic table explain the common connection between electronic structure and periodic accommodation capacities purpose of chemical elements in short form. For example, 1s orbital can have only two electrons, hence period one contains only two elements.

Period 6 includes 6s, 4f, 5d, and 6p orbitals in their electronic structure. Therefore, the period 6 contains a total of (2 + 14 + 10 + 6) = 32 elements from cesium to radon. Such a simplified scientific formula in chemistry is used to calculate the number of chemical elements in each period of the periodic table families.

Frequently Asked Questions

How many elements are on the periodic table?

There are 118 elements arranged in order of increasing atomic number in the modern periodic table.

What is Mendeleev’s periodic table?

Mendeleev in 1861 attempted to classify chemical elements in some order to explain their properties. The Mendeleev periodic law states that the physical and chemical properties of chemical elements are a period function of their atomic weights. He arranged the elements in groups (vertical columns) and periods (horizontal rows) in increasing order of their atomic weights.

What is the periodic table of elements?

A periodic table in chemistry is a tabular representation of 118 chemical elements in order of increasing atomic number or the full number of protons in the atomic nucleus.

How many periods are in the periodic table?

The modern form of the periodic table contains seven (7) periods for the accommodation of 118 chemical elements.

How many groups are in the modern periodic table?

The modern form of the periodic table contains eighteen (18) groups for the accommodation of 118 chemical elements.

Why periodic table is important in chemistry?

  • The periodic table is important in chemistry because it provides a tabular display of chemical elements on the basis of atomic number and electronic configuration.
  • It provides trends in element properties like electronegativity, ionization energy, atomic radius, and oxidizing and reducing properties. Therefore, it provides quick information about chemical elements.
  • The table can also be used to predict the properties of undiscovered chemical elements.

How is the modern periodic table arranged?

The modern periodic table arrangement comes due to the breakdown of Mendeleev’s (1861) scientific classification based on the atomic weight or masses of the chemical elements. In the modern periodic table, the list of 118 chemical elements is arranged in groups and periods on the basis of their atomic number and electronic configuration.

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