The Periodic Table Is A Tabular Arrangement of the Chemical Elements, Organized on the Basis of Their Atomic Numbers, Electron Configurations (Electron Shell Model), and Recurring Chemical Properties. Elements Are Presented in Order of Increasing Atomic Number (the Number of Protons in the Nucleus). The Standard form of the Table Consists of A Grid of Elements Laid Out in 18 Columns and 7 Rows, With A Double Row of Elements Below That. The Table Can Also Be Deconstructed Into Four Rectangular Blocks: the s-block to the Left, the p-block to the Right, the d-block in the Middle, and the f-block Below That. The Rows of the Table Are Called Periods; the Columns are Called Groups, With Some of these having names such as halogens or noble gases. Since, by definition, a periodic table incorporates recurring trends, any such table can be used to derive relationships between the properties of the elements and predict the properties of new, yet to be discovered or synthesized, elements. As a result, a periodic table—whether in the standard form or some other variant—provides a useful framework for analyzing chemical behavior, and such tables are widely used in chemistry and other sciences.

• Groups or Family

  Is a Column of Elements in the Periodic Table of the Chemical lements. There are 18 numbered groups in the periodic table, but the f-block columns (between groups 2 and 3) are not numbered. The elements in a group have similar physical or chemical characteristic of the outermost electron shells of their atoms ( the same core charge), as most chemical properties are dominated by the orbital location of the outermost electron.

Table

Periods

In the periodic table of the elements, elements are arranged in a series of rows (or periods) so that those with similar properties appear in a column. Elements of the same period have the same number of electron shells; with each group across a period, the elements have one more proton and electron and become less metallic. This arrangement reflects the periodic recurrence of similar properties as the atomic number increases. For example, the alkaline metals lie in one group (group 1) and share similar properties, such as high reactivity and the tendency to lose one electron to arrive at a noble-gas electronic configuration. The periodic table of elements has a total of 118 elements.

• $First$ $Period$

The first period contains fewer elements than any other, with only two, hydrogen and helium. They therefore do not follow the octet rule. Chemically, helium behaves as a noble gas, and thus is taken to be part of the group 18 elements. However, in terms of its nuclear structure it belongs to the s block, and is therefore sometimes classified as a group 2 element, or simultaneously both 2 and 18. Hydrogen readily loses and gains an electron, and so behaves chemically as both a group 1 and a group 17 element.

Hydrogen $(H)$ is the most abundant of the chemical elements, constituting roughly 75% of the universe's elemental mass.[1] Ionized hydrogen is just a proton. Stars in the main sequence are mainly composed of hydrogen in its plasma state. Elemental hydrogen is relatively rare on Earth, and is industrially produced from hydrocarbons such as methane. Hydrogen can form compounds nt in water and most organic compounds.

Helium $(He)$ exists only as a gas except in extreme conditions. It is the second lightest element and is the second most abundant in the universe. Most helium was formed during the Big Bang, but new helium is created through nuclear fusion of hydrogen in stars. On Earth, helium is relatively rare, only occurring as a byproduct of the natural decay of some radioactive elements. Such radiogenic helium is trapped within natural gas in concentrations of up to seven percent by volume.

• $Second$ $Period$

Period 2 elements involve the 2s and 2p orbitals. They include the biologically most essential elements besides hydrogen: carbon, nitrogen, and oxygen. Lithium (Li) is the lightest metal and the least dense solid element. In its non-ionized state it is one of the most reactive elements, and so is only ever found naturally in compounds. It is the heaviest primordial element forged in large quantities during the Big Bang.

Beryllium $(Be)$ has one of the highest melting points of all the light metals. Small amounts of beryllium were synthesised during the Big Bang, although most of it decayed or reacted further within stars to create larger nucleii, like carbon, nitrogen or oxygen. Beryllium is classified by the International Agency for Research on Cancer as a group 1 carcinogen. Between 1% and 15% of people are sensitive to beryllium and may develop an inflammatory reaction in their respiratory system and skin, called chronic beryllium disease.

Boron $(B)$ does not occur naturally as a free element, but in compounds such as borates. It is an essential plant micronutrient, required for cell wall strength and development, cell division, seed and fruit development, sugar transport and hormone development , though high levels are toxic.

Carbon $(C)$ is the fourth most abundant element in the universe by mass after hydrogen, helium and oxygen and is the second most abundant element in the human body by mass after oxygen, the third most abundant by number of atoms. There are an almost infinite number of compounds that contain carbon due to carbon's ability to form long stable chains of C—C bonds. All organic compounds, those essential for life, contain at least one atom of carbon; combined with hydrogen, oxygen, nitrogen, sulfur, and phosphorus, carbon is the basis of every important biological compound.

Nitrogen $(N)$ is found mainly as mostly inert diatomic gas, N2, which makes up 78% of the Earth's atmosphere. It is an essential component of proteins and therefore of life.

Oxygen $(O)$ comprising 21% of the atmosphere and is required for respiration by all (or nearly all) animals, as well as being the principal component of water. Oxygen is the third most abundant element in the universe, and oxygen compounds dominate the Earth's crust.

Fluorine $(F)$ is the most reactive element in its non-ionized state, and so is never found that way in nature.

Neon $(Ne)$ is a noble gas used in neon lighting.

• $Third$ $Period$

All period three elements occur in nature and have at least one stable isotope. All but the noble gas argon are essential to basic geology and biology.

Sodium $(Na)$ is an alkali metal. It is present in Earth's oceans in large quantities in the form of sodium chloride (table salt).

Magnesium $(Mg)$ is an alkaline earth metal. Magnesium ions are found in chlorophyll.

Aluminium $(Al)$ is a poor metal. It is the most abundant metal in the Earth's crust.

Silicon $(Si)$ is a metalloid. It is a semiconductor, making it the principal component in many integrated circuits. Silicon dioxide is the principal constituent of sand.

Phosphorus $(P)$ is a nonmetal essential to DNA. It is highly reactive, and as such is never found in nature as a free element.

Sulfur $(S)$ is a nonmetal. It is found in two amino acids: cysteine and methionine.

Chlorine $(Cl)$ is a halogen. It is used as a disinfectant, especially in swimming pools.

Argon $(Ar)$ is a noble gas, making it almost entirely nonreactive. Incandescent lamps are often filled with noble gases such as argon in order to preserve the filaments at high temperatures.

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