Elements And Atomic Number

                          Many different types of atoms are called elements. Each element has a unique set of physical and chemical properties. Elements are a type of matter that can not be broken down into a simpler substance by chemical reaction. Some familiar elements are oxygen, carbon, sodium, gold, and hydrogen.

                          Elements are identified by the number of protons in their nucleus, known as the atomic number ( Z ). An element's atomic number ( Z ) also indicates the same number of electrons in the neutral atom.

For Example :

Hydrogen                                                                    Helium

Z = 1                                                                           Z = 2

Proton - 1                                                                    Proton - 2

Electron - 1                                                                 Electron - 2

(Remember atoms have an equal number of protons and electrons.)

                All elements are organized according to their atomic number in the periodic table. In the periodic table, the order of an element's atomic number increases from left to right and top to bottom. Elements are further organized as columns based on their properties. Elements in the same column have similar physical and chemical properties. Many elements are represented by their English names and chemical symbols.

Example:

Hydrogen - H

Helium - He

            Some elements are represented by their Latin names and chemical symbols. 

Example:

Mercury - chemical symbol Hg. It comes from the Latin name of Hydrargyrum.

Lead - chemical symbol Pb. It comes from the Latin name of Plumbum.

                In the periodic table, the boxes of each element will always contain atomic number, chemical symbol, name, and atomic mass.

Explanation:

                 At the top of the box Hydrogen atomic number is 1. Below that Hydrogen chemical symbol H followed by its name Hydrogen. The bottom number is the Atomic mass. Hydrogen atomic mass 1.008

Atomic Structure ( Atoms )

 Atomic Structure:

       The arrangements of protons, neutrons, and electrons within an atom.

What are atoms?

    Atoms are basic units of matter and building blocks of everything in the universe. They maintain all the properties of chemical elements. Atoms comprise smaller subatomic particles called protons, neutrons, and electrons.

Structure of atoms:

            outside the nucleus, we have electron clouds. The dense region at the center of an atom is the nucleus. It's made up of protons and neutrons. Neutrons have no charge ( neutral ). Protons are positively charged (1+). Electrons are negatively charged ( 1- ).

       The unit we used to express the masses of subatomic particles is the abbreviation of unified atomic mass unit ( u ) AMU. Protons and neutrons have similar mass unit 1u. All the mass of an atom is the nucleus not in the electron cloud.

Properties Of Boric Acid

                Boric acid reacts with sodium hydroxide to form sodium metaborate and sodium tetraborate. 

                   H₃BO₃  +  NaOH  ———>  NaBO₂  +  2H₂O

                  4H₃BO₃  +  2NaOH  ———>  Na₂B₄O₇  +  7H₂0

Action Of Heat:

              Boric acid heated above 170 degree Celsius to gives metaboric acid.

                                 4H₃BO₃  ———>  4HBO₂  +  H₂0

              Boric acid heated above 300 degree Celsius to gives tetraboric acid.

                               4HBO₂   ———>  H₂B₄O₇  +  H₂O

             Tetraboric acid heated above 330 degree celsius to gives boron trioxide.

                               H₂B₄O₇  ———>  2B₂O₃  +  H₂O

Action Of Ethyl Alcohol:

              Boric acid reacts with ethyl alcohol in the presence of concentrated sulphuric acid to form triethylborate. The ethyl borate burns with green edged flame.

                              4H₃BO₃  +  3C2H5OH   ———>   B(OC2H5)3  +  3H2O

Action Of Calcium Fluoride:

            Boric acid reacts with calcium fluoride in the presence of concentrated sulphuric acid to gives boron trifluoride.

                            2H3BO3  +  3CaF₂  +  3H₂SO₄   ———>  2BF₃  +  3CaSO₄  +  6H₂O

Preparation Of Boric Acid

 Boric Acid:

             A mixture of concentrated sulphuric acid reacts with borax to form boric acid.

Na₂B₄O₇  +  H₂SO₄  +  5H₂O ———>      Na₂So₄          +          4H₃BO₃

                                                          ( Sodium sulfate )        ( Boric acid ) 

Boric acid can be extracted from colemanite. 

Ca₂B₆O₁₁  +  11H₂O₄  +  SO₂  ———>  Ca(HSO₃)₂  +  6H₃BO₃

Uses Of Boric Acid

• Boric acid is used in the manufacture of pottery glaze glass, enamels and pigments.
• Boric acid is used as an antiseptic, insecticide and flame retardants.
• Boric acid is used as a food preservatives.
• Boric acid is used in the production of LCD flat panel display.
• Boric acid is used to prevent existing wet and rot in timber etc....

Uses Of Borax

 Borax Uses:

• Borax is used fir the identification of colored metal ions.
• Peroxoborate present in washing powder. It's a cleaning and bleaching agent.
• Borax is a flux for soldering. And also acts as a good preservative.
• In the manufacture optical and borosilicate glass, enamels and glazes for pottery.
• Borax is used as fungicide, fire retardant and in softening water.
• Borax is used for stiffening agent for candle wicks. 
• Borax is used as antiseptic soaps.

Properties Of Borax

Properties Of Borax:

• Borax is a white crystalline solid, less soluble in water but more soluble in hot water.
• Borax dissolved in hot water to gives the alkaline solution of boric acid and sodium hydroxide.

                    Na₂B₄O₇  +  7H₂O  ———>  4H₃BO₃  +  2NaOH

• On heating, borax loses its water of crystallization and swells up to form a puff mass. On further heating, it melts into a clear liquid which solidified to a transparent glass like bead. Which consist of sodium metaborate and boric anhydride. This glass bead is commonly called as borax bead.                                                                                

                     Na₂B₄O₇.10H₂0 ———> Na₂B₄O₇ ———> 2Na₂BO₂ + B₂O₃

• Borax beads are used in laboratory to identify some metals in salts, through borax beads test. Nickel salts give brown colored bead. Cobalt slats give blue colored bead. White chromium salt gives green bead in flame.
• Borax reacts with acids like sulphuric acid and hydrochloric acid to form sparingly soluble boric acid.

                              Na₂B₄O₇ + 2HCl + 7H₂O  ———> 4H₃BO₃  +  2NaCl

                              Na₂B₄O₇  +  H₂SO₄  +  5H₂O  ———>  4H₃BO₃  +  2Na₂SO₄

• Borax reacts with Ammonium Chloride to form boron nitride.

                              Na₂B₄O₇  +  2NH₄Cl  ———>  2NaCl  +  2BN  +  B₂O₃  +  2H₂O

• Borax heated with ethyl alcohol and concentrated sulphuric acid, to forms vapors of triethylborane. When ignited these vapor burn with green edged flame.

                  Na₂B₄O₇  +  H₂SO₄  +  5H₂O ———> Na₂SO₄  +  4H₃BO₃

                  H₃BO₃  +  3C₂H₅OH  ———>  B(OC₂H₅)₃  +  3H₂O

Borax Preparation

 Borax  [Na₂B₄O₇.10H₂O]              

          Borax is a sodium salt of tetraboric acid. Fine powdered colemanite ( Ca₂B₆O₁₁ ).    Is boiled with sodium carbonate ( washing soda ) solution. The insoluble calcium carbonate is filtered off ( CaCO₃ ).  Then it is concentrated and cooled to get the crystals of borax. The sodium metaborate is treated with           CO₂  gas which converts into borax.

Ca₂B₆O₁₁  +  2Na₂CO₃  ———>  Na₂B₄O₇     +      2NaBO₂         +        2CaCO₃

Colemanite                                  Borax                 Sodium                     calcium

                                                                            metaborate                carbonate

2NaBO₂  +  CO₂  ———>  Na₂B₄O₇  +  Na₂CO₃

Uses Of Boron

 Boron Uses:

• The compound of boron are boric acid, borax and boric oxide. These can be found in eye drops, mild antiseptics, washing powders and title glazes. Borax used to make bleach and food preservative.
• Amorphous boron is used as a rocket fuel igniter.
• In the manufacture of pyrex glass, boric acid is used
• Sodium octaborate is a flame retardant.
• Boron is essential for the cell walls of plants.
• Boron has the capacity to absorb neutrons. This means the isotope of Boron-10 used to regulate nuclear reactors.

Chemical Properties Of Boron

                           The impure amorphous product a brownish black powder, was the only form of boron known for more than a century. Many of its compounds are electron deficient and has unusual type of covalent bonding which is due to its small size, high ionization energy and similarity in electronegativity with carbon and hydrogen. Pure crystalline boron may be prepared by reduction of its bromide or chloride with hydrogen on an electrically heated tantalum filament.

Boron Trihalides:

                 Boron reacts with halogen elements to form highly reactive trihalides. Boron trihalides and trimethylamine reacted to form complex. 

                  BCl₃  +  N(CH₃)₃  ———>  (CH₃)₃N.BCl₃

Formation Of Hydrides:

                  With hydrogen boron forms a series of compounds called boranes. The simplest borane is Diborane ( B₂H₆ ). Boron trifluoride react with sodium hydride around 450K ( Heat ) to form diborane.

                 2BF₃  +  6NaH  ———>  B₂H₆  +  6NaF

Formation Of Boron Oxides:

                       Boron reacts with oxygen around 900K ( heat ) to  form its oxide. 

                   4B  +  3O₂  ———>  2B₂O₃

Reaction With Acid And Alkali:

                        Boron is most easily converted into boric acid by treatment with acids like sulphuric acid and nitric acid.

                     2B  +  3H₂SO₄  ———>  2H₃BO₃  +  3SO₂

                     B  +  3HNO₃  ———>  H₃BO₃  +  3NO₂

Boron reacts with sodium hydroxide to form sodium borate.

                    2B  +  6NaOH  ———>  2Na₃BO₃  +  3H₂

                  

Boron Group Elements ( Group- 13 )

 Boron Family:

               The group 13, boron group consist of six elements. The elements are Boron ( B ), Aluminum ( Al ), Gallium ( Ga ), Indium ( In ), Thallium ( Tl ). The common property of the group is that each one of the elements has three electrons in the outer shell of their nuclear structure. Boron is the lightest element in this group. Relatively rare element. Boron is a metalloid.

Occurrence Of Boron Family:

• Boron is a very low in abundance, composing only 0.0001% of the earth's crust.
• Aluminium is the most abundant metal and occurs as oxides and also found in Aluminium silicate rocks. It composes about 8.3% of the earth crust.
• Gallium is relatively rare element in the earth's crust. Gallium find in the earth with a wealth of 13 parts per molecule.
• Indium is the 61st richest element in the world's covering.
• Thallium is found in small amounts all over the planet. Thallium is extremely toxic and has no commercial use. The elements Ga, In, and Tl occurs as their sulphides.

Allotropy

                 Some chemical elements exist in two or more different forms in the same physical state known as Allotropes of elements. In greek "allos" means another and trope means change. 

For example: Carbon exists as diamond and graphite. This phenomenon is called allotropism and the different forms of elements are called allotropes.

Allotropes of some elements:

Non-metals:

Carbon           -- Diamond, Graphite, Amorphous carbon, Fullerenes, Graphene, Carbon nanotubes.

Oxygen          -- Dioxygen, Ozone, Octaoxygen.

Selenium        -- Red selenium, Gray selenium, Black selenium, Monoclinic selenium.

Phosphorus    -- White phosphorus, Red phosphorus, Violet phosphorus, Black phosphorus, Scarlet                                          phosphorus.

Sulphur          -- Rhombus sulphur, Monoclinic sulphur.

Metalloids :

Tellurium     -- Amorphous tellurium, Crystalline tellurium.

Boron.          -- Amorphous boron,  ⍺ - rhombohedral boron, β - rhombohedral boron, 𝛾 - orthorhombic                                boron, ⍺ - tetragonal boron, β -tetragonal boron.

Germanium  --  ⍺ - germanium, β - germanium.

Arsenic         -- Yellow arsenic, Gray arsenic, Black arsenic.

Antimony     --  Yellow antimony, Black antimony, Blue-White antomony.

Silicon.         --  Amorphous silicon, Crystalline silicon.

Metals:

Tin        --  Gray tin, White tin, Rhombic tin, Sigma tin.

Iron      --  Ferrite, Austenite.

cobalt   --  ⍺ - cobalt, β - cobalt.    

  

Reduction Of Metal Oxides

          Extraction of metals from their respective ores. In this method we can get metal oxides again we adding some reducing agent and heated up. It will give pure metals.

Smelting:

     Smelting is a process of reduction of metal oxide to metal by carbon, carbon monoxide, or aluminum. In this metal oxide is heated above the melting point of the metal.

Example: 

Oxide of ion can be reduced by carbon monoxide.

Fe₂O₃  +  3CO  ———>  2Fe   +   3CO₂            

         Limestone ( CaO ) is a basic flux. Silica gangue present in the ore in its acidic nature. The limestone combines with silica gangue to form calcium silicate( slag ). 

  CaO    +      SiO₂      ———>    CaSiO₃

(Flux)       ( Gangue)                      (Slag)

             The concentrated ore ( copper pyrite ) heated in a reverberatory furnace. It will form metal sulphides FeS and Cu₂S. Both are soluble and form a copper matte.

2CuFeS₂  +  O₂  ———>  2FeS  +  2Cu₂S  +  2SO₂

FeS oxidized to FeO.

FeS  +  O  ———>   FeO   +   SO₂

Now the ferrous oxide ( flux ) reacted with the silica ( gangue ) to form ferrous silicate  ( slag ).

    FeO     +       SiO₂       ———>      FeSiO₃

  (Flux)        (  Gangue)                      (Slag)

The remaining copper sulphide is further oxidised to its oxide to form the metallic copper.

Cu₂S  +  3O₂  ———>  2Cu₂S  +  2SO₂

2Cu₂O  +  Cu₂S  ———>  6Cu  +  SO₂

This metallic copper  has blistered appearance due to the evolution of   SO₂  gas. This copper is called Blistered copper.

Reduction By Carbon:

        In this method oxide ( ZnO ) ore is mixed with coal ( Coke ) and heated strongly in a furnace. This process only applied to the metal which do not form carbides with carbon. 

Examples :

ZnO  +  C  ———>  Zn  +  CO

Mn₃O4  +  4C  ———>  3Mn  +  4CO

Cr₂O3  +  3C  ———>  2Cr  +  3CO

Reduction Of hydrogen;

              This process only applied to the metal which have less electro -positive character than hydrogen.

Ag₂O  +  H₂  ———>  2Ag  +  H₂O

Fe₂O4  +  4H₂  ———>  3Fe  +  4H₂O

Reduction By Metal:

B₂O₃  +  6Na  ———>  2B  +  3Na₂O

Rb₂O3  +  3Mg  ———>  2Rb  +  3MgO

TiO₂  +  2Mg  ———>  Ti  +  2MgO

In this process metal oxides reduced by metal.