The Periodic Table By Aditi Atmasidha

Introduction Many scientists tried to arrange elements in a group or table having certain characteristics to arrange in chronological order, this table later came to be known as the Periodic table. Initially very few elements were represented by their pictorial signs. Later more and more elements were discovered. They were represented by their symbols as suggested by Berzelius. For example: C carbon N nitrogen Ca

calcium

Pictorial signs for Elements

Early Discoveries and ideas about Periodic

Table Studies of Different Scientists.

Johann Dobereiner• Johann Dobereiner was the first scientists who

tried to classify elements. He arranged the elements of similar chemical properties in a group of three of their increasing atomic weights.

• He found that the atomic weight of middle weight = arithmetic mean of other two elements. He named the group of these three elements as triads. But he could not arrange all the available elements in a triad.

Dobereiner’s Triads

John Newlands Octaves

• He arranged the known elements in the increasing number of their atomic weights. He found that the properties of every eighth element is same as property of first element like an octave of music.

• But the element with higher atomic weights do not follow these rules.

Dimitri Mendeleev • Mendeleev arranged elements in the increasing

order of their atomic weights. He found that properties of elements are periodic functions of their atomic weights. He kept three vacant places in his periodic table for three unknown elements and predicted their properties.

• He named these elements as Eka-Boron, Eka-Aluminum And Eka-silicon. After discovery their properties were found to be true and were named as scandium, gallium and germanium.

Drawbacks of Mendeleev’s periodic

Table • Isotopes have separate places in his periodic

table. • Some elements having higher atomic weight were

placed before elements having lower atomic weights.

• Noble gases do not have place in his periodic table.

• Elements with different chemical properties are placed in the same group while with same properties are placed in different group.

Mendeleev’s periodic Table

The Modern Periodic Table Exploitation

Introduction. • It was suggested by Moseley. Modern periodic law

says the properties of elements are periodic functions of their atomic number.

• The periodic table is an arrangement of the elements according to similarities in their chemical and physical properties.

• Periodic table is displayed in seven different rows called PERIODS.

Periods of Periodic Table

Periods Description of that period

1st period Hydrogen & Helium

2nd period Eight elements starts from lithium and ends with neon

3rd period Eight elements starts sodium and ends with Argon

6th period Thirty - two elements lanthanides are present.

7th period Thirty – two elements actinides are present.

Groups of Periodic table

Group 1 Alkali Metals

Group 2 Alkaline Earth Metals

Group 7 Halogens

Group 8 Noble Gases

Groups of Periodic table

Alkali Metals • The alkali metals are a group in the periodic table

 consisting of the chemical elements lithium (Li), sodium (Na), potassium(K), rubidium (Rb), caesium (Cs), and francium (Fr).

• The alkali metals have very similar properties: they are all shiny, soft, highly reactive metals at standard temperature and pressure and readily lose their outermost electron to form cations with charge +1. They can all be cut easily with a knife due to their softness, exposing a shiny surface that tarnishes rapidly in air due to oxidation. Because of their high reactivity, they must be stored under oil to prevent reaction with air, and are found naturally only in salts and never as the free element.

Alkali Metals { Examples }

Alkali metal Melting point Boiling point[8] Density(g/cm3)

Lithium180.54 °C,

1342 °C, 0.534

Sodium 97.72 °C,883 °C,

0.968

Potassium63.38 °C, 759 °C,

0.89

Alkali Metal { Reactions }

Metals Lithium Sodium Potassium

Reaction with water

Fizzes and floats on water, Lithium Hydroxide is produced in Liquid state and Hydrogen escapes.

Fizzes more strongly’ Sodium Hydroxide is produced and Hydrogen escapes.

Burst into flame due to heat liberation, Potassium Hydroxide is produced and Hydrogen burns with flame.

Reaction with air

Burns in air to produce solid Lithium Oxide.

Burns in air to produce solid Sodium Oxide.

Burns in air to produce solid Potassium Oxide.

Reaction with Halogens

Alkali Metals react strongly with Halogens to form Halides. { LiCl }

Alkali Metals react strongly with Halogens to form Halides.{ NaCl }

Alkali Metals react strongly with Halogens to form Halides. .{ KCl }

Alkali Metal { Uses }Lithium Sodium Potassium

Batteries Street lamps to give orange glow

Potassium nitrate is used as fertilizer and explosive.

Medicines to treat mental disorder

Alloyed with potassium to make material for transferring heat in Nuclear reactor.

In the body potassium ions are used for control of water content of the blood.

Sodium Hydroxide is used to prepare cosmetics, soaps etc.

In the body potassium ions are needed to send nerve impulses.

In the body Sodium ions are needed to send nerve impulses.

Alkaline Earth Metals • The alkaline earth metals are a group of 

chemical elements in the periodic table with very similar properties. They are all shiny, silvery-white, somewhat reactive metals at standard temperature and pressure and readily lose their two outermost electrons to form captions with charge 2+ and an oxidation state, or oxidation number of +2. The alkaline earth metals are beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr),barium (Ba), and radium (Ra).

Alkaline Earth Metals { Examples }

Alkaline earth metalMelting point

(°C)Boiling point

(°C)[6]

Density(g/cm3)

Beryllium 1287 2469 1.85

Magnesium 650 1090 1.738

Calcium 842 14841.54

Alkaline Earth Metals { Reactions }

Metals Beryllium Magnesium

Calcium Strontium

With oxygen in Air

No reaction Forms Magnesium Oxide on the metal surface.

Forms Calcium Oxide on the metal surface.

Forms Strontium Oxide on the metal surface.

With pure oxygen

Forms Beryllium Oxide.

Forms Magnesium Oxide.

Forms calcium Oxide.

Forms Strontium Oxide.

With Water No reaction Magnesium Hydroxide & release Hydrogen

Calcium Hydroxide & release Hydrogen

Strontium Hydroxide & release Hydrogen

Alkaline Earth Metals { Uses}

Beryllium Magnesium Calcium

Alloyed with other metals to form strong and light weight alloys.

Use din fireworks to make brilliant white light.

Used in production of baking powder, bleaching powder medicines and plastics.

Rods are used in nuclear reactors to control speed of Neutrons.

Alloyed with other metals to make strong and light weight alloy which can be used to make bicycle frames.

It is needed in the body for the formation of strong and healthy bones and teeth.

Combines with aluminum, silicon and oxygen to form mineral called Beryl.

Green plants need magnesium to make chlorophyll.

In human body it is needed for contractions of muscles.

Emerald and aqua marine are two varieties of Beryl's that are used as gemstones in jewellery.

It is needed in the body for the formation of strong and healthy bones and teeth.

Calx- Latin name for lime { Calcium Oxide }

Halogens { Salt Formers }

• The halogens or halogen elements are a group in the periodic table consisting of five chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). The group of halogens is the only periodic table group that contains elements in all three familiar states of matter at standard temperature and pressure. All of the halogens form acids when bonded to hydrogen. Most halogens are typically produced from minerals or salts. The middle halogens, that is, chlorine, bromine and iodine, are often used as disinfectants. The halogens are also all toxic. 

Halogens {Examples}

HalogenMelting point

(°C)Boiling point

(°C)[18]

Density(g/cm3at 25 °C)

Fluorine −219.62 −188.12 0.0017

Chlorine −101.5 −34.04 0.0032

Bromine −7.3 58.8 3.1028

Halogens { Reactions }

Halogens Fluorine Chlorine Bromine

With noble gases

Most reactive element. Reacts with Nobel gases to form compounds.

No reaction No reaction

With water Reacts vigorously with water to form Hydrogen Fluoride and oxygen.

Dissolves in water and reacts with it to form Hydrochloric acid and Hypochlorous acid .

Dissolves in water and reacts with it slowly to form Hydrogen bromide and Hypobromous acid .

Halogens {Uses}Fluorine Chlorine Bromine

One of the component of CFC.

One of the component of CFC.

Used with silver in traditional photography.

Hydrogen Fluoride dissolves glass and is used in etching glass surface.

In combination with sodium as rock salt.

Sodium Fluoride prevents tooth decay and is added in drinking water supplies.

Used as water disinfectant in the manufacture of bleach.

Combines with Calcium to form Fluorite, it is used to make ornaments and Jewelry.

To produce acid which has many uses in Industry.

Nobel Gases Helium Neon Argon Krypton Xenon

Lighter than air. Used to lift meteorological balloons in the atmosphere.

Produces red light with electrical current flows through it.

Used in wire filament bulbs.

Used in lamps that produce light of high intensity.

To make bright light in photographers flash gun.

Mixes with oxygen to help deep sea diverse breathe under water.

Used in lights for advertising displays.

Used in making silicon and germanium crystals for electronic industries.

Used for airport landing lights and in light houses.

Hydrogen • Has unique properties, its properties do not

match well with properties of other elements. • It has no neutrons only one proton and one

electron, this makes Hydrogen the lightest atom. • It is colourless gas without any odour or smell and

is most common element in the universe.

Reactions of Hydrogen • It combines with carbon to make Hydrocarbons

found in oil. • Combines with nitrogen to make ammonia for use

in fertilizers. • It burns itself when heated • If it is mixed with air or oxygen before it is ignited it

explodes and can cause great deal of damage. • It can form many compounds by mixing with

Carbon, Oxygen, Halogens.• It is component of acids ,hydroxides, hydrogen

carbonates. • Hydrogen is used as fuel in car.

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