Discovery of Atom

Introduction 
The term atom has its origin from the Greek word ‘átomos’ which means indivisible or, uncuttable, something that cannot be divided further. Indian and Greek philosophers first proposed the concept of an atom as an indivisible component of matter. Chemists provided a physical basis for this idea in the 17th and 18th centuries, by showing that certain substances could not be further broken down by chemical methods.



      Picture of an atom 1

Discovery of atom

Way back in 300-400B C, Democritus and Epicurus the greatest Greek philosophers proposed that there were indivisible atoms having a size, weight and shape. They stated that everything in the universe was made of those indivisible atoms including human's body and soul.  They also suggested that in empty space atoms could move uniformly and they could also vibrate at random and turn.

In 1803 John Dalton, English instructor and philosopher, used this concept of atoms and explained that elements always react in ratios of small whole numbers. He also explained that certain gases dissolve better in water than others. He theorized that every element consists of atoms of a single type, and that these atoms can join together to form chemical compounds. Dalton is regarded the originator of modern atomic theory.

The atom is the simplest unit of matter which consists of a nucleus at the center and is surrounded by negatively charged particles called electrons. The nucleus consists of protons that are positively charged and neutrons that are neutral in charge. The electrons are bound to the nucleus with the electromagnetic force. Two or more atoms together form a molecule. If the atom has equal number of protons and electrons, it is called electrically neutral, however if the protons are more, the atom is called as positively charged and if electrons are more, it is called negatively charged.

However, during the end of 19th and early 20th centuries, physicists have discovered subatomic components and structure inside the atom, and thereby proved that the 'atom' was indeed divisible. Scientists have used many principles of quantum mechanics in order to explain the model of the atom.

Conclusion to the discovery of atom

The discovery of atom was the major milestone in science. This enabled the formulation of periodic table and brought major advancement in science.

Basic structure of an atom

Introduction

The atom is the building block of the substance; each and every thing is made up of atom. In earlier concept it was thought that atom was indivisible, with the advancement in the technology and after a lot of results and experiments it is now proved that atom can further be divided in to more fundamental particle. Ruther ford on the basis of his experiment of scattering of alpha particle through the gold foil drew following conclusions.

Basic structure of an atom

Most of the part of the atom is hollow, approximately all the mass of the atom is concentrated to a very small region called the nucleus compare to the atom the nucleus is very small, the radius of the atom is of the order of 10^-10 meter while the radius of the nucleus ids of the order of 10^-15 meter, therefore the nucleus is about 10^5th part of the atom.

Protons and the neutrons reside in the nucleus while electrons revolve round the nucleus in the different orbits. Bohr’s gave the idea of the stationary orbit, according to him the electrons move round the nucleus in the stationary orbit, the stationary orbits are those in which the angular momentum of the moving electrons is conserved , so it does not lose its energy, these stationary orbits are called energy levels , and are represented by the capital letters, K,L,M,N etc, according to 

Bohr’s scheme the maximum number of electron that can occupy a hell is given by the formula 2n² , where n is the number of shell, using this formula it is clear that the number of an electron that can be accommodated in 1, 2,3and4 shell is  2,8,18 and 32  respectively,

The shell is further divided in to sub shells and the sub shells are composed of the orbitals , there are different type of orbitals like s,p,d,,f,g etc, according to quantum mechanical model the electrons have dual nature they have both particle as well as the wave nature. They are like stationary waves’ round the atoms, and the orbital s are nothing but wave functions.

There are more fundamental particles which are discovered apart from the neutrons, protons and electrons , these are different types of mesons, neutrino quark etc.the scientific advancement is a continuous process and scientist are in the constant effort to find the ultimate particles called the god particles which are the building block of all kind of matter.

Argon atom

Argon is basically a Greek word, argos meaning lazy. It was suspected in 1785 that it was present in air by Henry Cavendish. Later it was discovered by Lord Rayleigh and Sir William Ramsay in 1894.

Introduction :
The Argon atom is the chemical element which is present in the eighteenth group of the periodic table. Argon atom symbol is Ar. It is having an atomic number 18 and atomic weight 39.948amu it’s equal to 40 amu. It belongs to eighteenth group, (viii A) period and it is a p-block element. It has 18 electrons and 18 protons and has 22 neutrons. Density of Argon atom is 1.784 kg/m^3. Argon atom belongs to noble gas series. It belongs to p–block is predicted by its electronic configuration. The electronic configuration is based on atomic number of an atom, so the electronic configuration of Argon atom is 1s² 2s² 2p⁶ o [Ne] 3s² 3p⁶, here the outermost electron present in the p-orbital so it belongs to p-block. It has cubic face centered crystal structure. It is diamagnetic in nature. It is the third noble gas.

Electron Shell model of Argon atom

It has 3 main isotopes; they are Ar-40, Ar-36, and Ar-38. Ar -39 is made by cosmic ray activity. Ar-40 is produced by neutron capture method from K -39 and also by alpha emission by calcium and Ar-37 is produced by the decay of Ca -40.

Physical properties of argon atom:

1. It is a non-metallic, colorless and odorless  gas at room temperature i.e. at 298K.
2. Its melting point and boiling point are 83.8K and 87.3K respectively.
3. It occupies about 1% of Earth’s atmosphere.
4. It is chemically inert so it does not react with any element or a molecule.
5. It is stored at high pressures.

Applications of argon atom:

Argon atom is used

1.     In  lighting due to its high stability AND it will not react with the filament in a bulb even under high temperatures

2.     Due to its inertness, it is used as inert gas shield in case of welding.

3.      In the manufacture of titanium as a non- reactive blanket and many more.

Aluminium atom

Introduction:
Aluminium atom is a silvery white member which belongs to the boron group element.  It has an atomic number 13 and Al is its symbol. Aluminium is the third most abundant metal in the Earth's crust, after oxygen and silicon. It makes up about 8% by weight of the Earth's solid surface. Aluminium is reactive chemically to occur in nature as a free metal. Instead, it is found combined in over 270 different other minerals. Bauxite ore is the chief source of aluminium.

One of the remarkable properties of Aluminium atom is for its low density metal and for its ability to resist corrosion due to the phenomenon named as passivation.

The property of Aluminium metal depends on Aluminium atoms present in it. Aluminium is a soft, durable, lightweight, ductile and malleable metal of the 3^rd period. Its appearance ranges from silvery to dull gray, depending on the surface roughness. Aluminium is nonmagnetic metal. It is also insoluble in alcohol, in certain forms though it can be soluble in water. 7–11 MPa is the yield strength of pure aluminium, while aluminium alloys yield strengths ranging from 200 MPa to 600 MPa. Aluminium atom has about one-third the density and stiffness of steel.

Face-centered cubic (fcc) structure is the atomic arrangement of Aluminium atoms.  Aluminium metal has a stacking -fault energy of approximately 200 mJ/m².

Characteristics of aluminium atom

Aluminium is a metal which is present in 13th (lllA) group and 3^rd period of the periodic table. It has the electronic configuration 1s²2s²2p⁶3s²3p. Aluminium has the Oxidation state of +1,+2, and +3.

The outer three electrons occupy three s²p hybrid orbitals that point in orthogonal directions. These electrons easily form covalent bonds, as in anhydrous AlCl₃. This compound easily sublimates, showing that it is not ionic, and is partially hydrolyzed by H₂O to release HCl gas. It cannot be formed by heating the hydrated form to drive off H₂O.

3s²3p² 3p  is the spectroscopic ground state. The resonance line is at 396.15 nm of Aluminium atom, that’s why aluminium atom is not excited in the flame and gives it no color. When the atom is excited, most of the lines are in the red or infrared in nature. Aluminium is in column IIIA of the modern periodic table, which includes boron, aluminium, gallium, indium and thallium. Aluminium atom is the only common element in the group, and is considerably different from the others in physical and chemical properties.

Aluminium is the most widely used non-ferrous metal among the metals. Relatively pure aluminium is encountered only when corrosion resistance and workability is more important than strength or hardness. A thin layer of aluminium can be deposited onto a flat surface by physical vapour deposition or chemical vapour deposition or other chemical means to form optical coatings and mirrors on the surfaces.

Applications of aluminium atom

Other uses of Aluminium Atom: 

• Transportation: Here Aluminium is used as body parts such as automobiles, aircrafts, trucks, railway cars, marine vessels, bicycles etc. as sheet, castings etc.,
• Packaging of Food and other things are made by Aluminium foil.
• Construction of building materials. (Windows, doors, siding, building wire, equipments etc.)
• A wide range of household items, from cooking utensils to baseball bats, watches etc., are made from Aluminium atom.
• Street lighting poles, sailing ship mats, walking poles, roof cover etc., are made by strong Aluminium Rods.
• Outer shells of consumer electronics, also cases for equipment e.g. photographic equipment etc., are made from Aluminium.

Atomic number 68

Introduction :
The element in the periodic table with atomic number 68 is Erbium.  Erbium is a element which belongs to lanthanide series in the periodic table with atomic number 68 and the symbol is Er.  Naturally Erbium is found along with other elements on earth.  It is a rare earth element which is associated with mineral gadolinite from ytterby.  It has optical fluorescent properties which is useful in laser applications like laser optical amplifier. Glasses or crystals which are doped with the element atomic number 68 (erbium) are mainly used in amplification media.

Silvery white Erbium:                                         Erbium chloride showing pink fluorescense
                                                                        under sunlight
            

Occurrence of element with atomic number 68:
In the earth crust erbium has 2.8mg/kg concentration where as in sea water it has 0.9ng/L.  This element found bound with monazite sand ores.  The sources of erbium are xenotime and euxenite.

Monazite sand:



Isotopes of element with atomic number 68:
Erbium which occurs naturally is composed of 6 stable isotopes, Er-162, Er-164, Er-166, Er-167, Er-168, and Er-170 with Er-166 being the most abundant isotope.

Properties of Element with atomic number 68:

Physical properties of Element with atomic number 68:

1. It appears as silvery white but under sun light it shows pink fluorescence.
2. Erbium has density 9.006g/cm³.
3. It decomposes at 1802K.
4. It boils at 3141K.
5. Heat of fusion is 19.90kJ/mol.
6. Heat of vaporization is 280kJ/mol.
7. Specific heat capacity at 25⁰C is 28.12J/mol/K.
8. Below 19K it is ferromagnetic, between 19-80K it is antiferromagnetic and above 80K it is paramagnetic in nature.  

Chemical Properties of Erbium with atomic number 68:
1. Erbium metal burns to form erbium (III) oxide.
    4 Er + 3 O₂ → 2 Er₂O₃
2. It reacts slowly with cold water and quickly with hot water and forms erbium oxide.
    2 Er (s) + 6 H₂O (l) → 2 Er (OH) ₃ (aq) + 3 H₂ (g)
3. Erbium reacts with all the halogens
    2 Er (s) + 3 F₂ (g) → 2 ErF₃ (s) [pink]
    2 Er (s) + 3 Cl₂ (g) → 2 ErCl₃ (s) [violet]
    2 Er (s) + 3 Br₂ (g) → 2 ErBr₃ (s) [violet]
    2 Er (s) + 3 I₂ (g) → 2 ErI₃ (s) [violet]
4. Erbium dissolves readily in dilute sulfuric acid forms yellow [Er (OH₂)₉]³⁺ hydration complexes
    2 Er (s) + 3 H₂SO₄ (aq) → 2 Er³⁺ (aq) + 3 SO2−4 (aq) + 3 H₂ (g)

 Applications of element with atomic number 68:

1. Oxide erbium which has pink color is used as a colorant for glass, porcelain and cubic zirconia. These glasses are used in sunglasses and some jewelry.
2. These are used in neutron –absorbing  control rods.
3. When erbium is doped  with optical silica glass fibers, they are used widely in optical communications.
4. These are also used to create fiber lasers.
5. These are also used in metal welding and cutting applications.
6. Erbium ions have large variety  of medical applications.

Atomic Number 4

Introduction :
Beryllium is the compound which as atomic number 4 and mass number 9.01218.  Beryllium has electronic configuration 1s², 2s².  Beryllium has oxidation state +2.  Group 2 elements are Be, Mg, Ca, Sr, Ba, Ra are alkaline earth elements.  Atomic number 4 is a exception : it does not react with water or steam, and its halides are co-valent bond with beryllium.  All the alkaline earth metal as two electrons in the outermost shell, so filled electron shell is achieved by the lose of two electrons to form doubly charged positive ions.  Atomic number 4 is a bivalent element.  It is found naturally only combined with other minerals.  Notable gemstone which has Atomic number 4 include beryl (aquamarine, emerald) and chrysoberyl.  Atomic number is a steel – gray, strong,  light weight brittle alkaline earth metal.



 Beryllium (White grey metal).

1)      Atomic Radius of Group 2 elements: Atomic radius increases down the group.  Atomic radius of Ra is less than Ba.

Element	Be	Mg	Ca	Sr	Ba	Ra
A.R.(pm)	112	160	197	211	222	215

   Where A.R.  = Atomic Radius in pico metre.

2)      Density of beryllium is 1.848g/cm³.

3)      Ionisation energy (I.E.) of Atomic number 4:
       1^st I.E.  =     899.5 KJ/mol.
       2^nd I.E.  =   1757.7 KJ/mol.
       3^rd I.E.  =  14848.7KJ/mol.
        3^rd I.E. is very large because the electron is present near to the nucleous and strongly binded to the nucleous.  Therefore it requires more energy to remove that electron which is ns² configuration.

4)      Elecrtropositive character of  Group 2 elements: Electropositive character increases down the group.

5)      Metallic properties of Atomic number 4: Atomic number 4 has low density (1.85 times that of water), high melting point= 1287⁰C.  High temperature stability and low co-efficient of thermal expansion, These conditions is suitable for aerospace material,  Atomic number 4 is a important component of planned space telescope because of its relatively high transparency to X-ray.

6)Reaction of Atomic number 4 with air: Beryllium does not burn unless it is in the form of dust or powder.  Be has a thin layer of Beryllium oxide on its surface which prevent any new oxygen getting at the underlying Be to react.
               2Be_(s)      +    O_2(g)     →       2BeO_(s)

7)      Diagonal relationship of Atomic number 4: Beryllium shows diagonal relationship with Aluminium.  It is the similarity between the first element of a group with the second element in the next higher group.

8)      Ores of Beryllium:
a)      Betrandite      (Be₄si₂O₇(OH)₂)
b)      Beryl              (Al₂Be₃Si₆O₁₈)
c)      Chrysoberyl   (Al₂BeO₄)
d)     Phenakite        (Be₂SiO₄)
      Precious form of Beryl are aquamarine, bixbite and emerald.

Nomenclature of elements with atomic number > 100

Introduction :
In the periodic table the elements are arranged in the order of the atomic number.  Atomic number is nothing but it is the number of proton or number of electron in the neutral atom. It is denoted by the letter Z.

The modern periodic law states that “ the physical and chemical properties of the elements are periodic function of their atomic numbers.”
Periods constitutes a series of elements whose atoms have the same number of  electron shell i.e., principal quantum number (n). There are seven periods and each period starts with a different principal quantum number.

Transuranium elements are elements beyond uranium (Z=92) they all synthethic elements.   Element with atomic number 100 is called as Fermium and the elements beyond these element in the periodic table is called as transfermium element.  The element after atomic number 100 is normally named as famous scientist.  But there is a lot of ambiguity in the names.  In each country the name will differ.  Some of the elements will be having more than one names

For example Kurchatovium with atomic number 104 is also called as Rutherfordium
Neilsbohrium also known as Borium has atomic number of 107.

The discovererc of these elements normally decide the name of the element.  Since same element can be made in the laboratory by more htan one scientist more than one name existed

Some other common names or nomenclature of elements with atomic number > 100 are given as

Atomic Number	Name
Z = 105	Dubnium
Z = 106	Seaborgium
Z = 108	Hassnium
Z = 109	Meiternium

IUPAC nomeclature of elements with atomic number > 100

To over come this ambiguity International Union of Pure and Applied Science (IUPAC) has recommended a nomeclature for elements with atomic number greater than 100.
IUPAC has given the name using the Latin words for their numbers.  The root words for the names is given in the table

Numerical	Root Name
0	nil
1	un
2	bi
3	tri
4	quad
5	pent
6	hex
7	sept
8	oct
9	en

Name (Nomenclature) of some of the elements with atomic number > 100

Atomic number	Name of the element	Symbol
Z = 101	Unnilunnium	Unu
Z = 102	Unnilbium	Unb
Z = 103	Unniltrium	Unt
Z = 104	Unnilquadium	Unq
Z = 105	Unnilpentium	Unp
Z = 106	Unnilhexium	Unh
Z = 107	Unnilseptium	Uns
Z = 108	Unniloctium	Uno
Z = 109	Unnilennium	Une
Z = 110	Ununnilium	Uun
Z = 111	Unununium	Uuu
Z = 112	Ununbium	Uub
Z = 113	Ununtrium	Uut
Z = 114	Ununquadium	Uuq
Z = 115	Ununpentium	Uup
Z = 116	Ununhexium	Uuh
Z = 117	Ununseptium	Uus
Z = 118	Ununoctium	Uuo
Z = 119	Ununennium	Uue
Z = 120	Unbinilium	Ubn