Ionic radii table

What is Ionic Radii ?

Ionic radii is related to ions present in ionic substances (crystalline solids). Ions are formed when neutral atom either gain or lose electrons. The effective size of the cation (+ charged) or anion (- charged) is termed as ionic radius. It is defined as the distance between the nucleus and outermost shell of an ion or it is the distance between the nucleus and the point where the nucleus exerts its influence over the electron cloud.

Comparative size of the atoms and the cations in the table

Comparison of the ionic radii with corresponding atomic radii of the cation is always smaller than the atomic radii of the parent atom. The radius of the anion is always larger than the atomic radii of the parent atom.

Comparative size of the atoms and the cations in the table

Atom	Atomic radii (crystal radius)Ao	Corresponding cation	Ionic radii (Ao)
Li	1.52	Li+	0.59
Na	1.86	Na+	0.99
K	2.31	K+	1.33
Mg	1.60	Mg2+	0.65
Ba	2.22	Ba2+	1.35
Al	1.43	AL3+	0.50
Pb	1.75	Pb2+	1.32

Comparison of atoms and their anions in the table

Atom	Atomic radii (crystal radius)Ao	Corresponding cation	Ionic radii (Ao)
F	0.72	F­-	1.36
Cl	0.99	Cl-	1,81
Br	1.14	Br-	1.96
O	0.73	O2-	1.04
S	1.04	S2-	1.84
N	0.75	N3-	1.71
P	1.10	P3-	2.12

The Z/e Ratio and comparison of different radii

In any particular group, the ions either anions or cations increases as we move top to down, this is because the increase in the number of shell as observed in case of the atomic radius. The size of the cation decreases with the increase in the positive charge. And the size of the anion increase as the negative charge on the anion increases.

This can be explained on the basis of Z/e ratio, whenever this ratio increases, the size of the ion decreases.

Na	Na+	Cl	Cl-	Fe2+	Fe3+
Z/e=11/11=1	11/10=1.1	17/17=1	17/18=.95	26/24=1.08	26/23=1.13

Therefore the relation between the ionic radii and the ions would be:

 Na>Na⁺    Cl <Cl^-   Fe²⁺>Fe³⁺

Most reactive metals in the periodic table

Introduction :
A periodic table is an arrangement of all the known elements in vertical groups and horizontal rows so that the elements with similar physical and chemical properties are placed in the same group.In 1912, Moseley proposed the modern periodic law.  The modern periodic law states that the physical and chemical properties of the elements are periodic functions of their atomic numbers.  There are 18 vertical columns and 7 horizontal rows.The Vertical columns present in the periodic table are represented by Groups.  The horizontal rows present in the periodic table are represented by Periods.

The most reactive metals in the periodic table are:

• Lithium( Li)
• Sodium (Na)
• Potassium(K)
• Rubidium(Rb)
• Caesium(Cs)
•  Francium(Fr)

These elements are called Alkali Metals Periodic Table because their oxides and hydroxides dissolve in water to produce strong alkalies.  They are most reactive and highly electropositive elements in the periodic table.  Group first elements of the periodic table are called as alkali metals.  These are very reactive metals we cannot get freely in nature.  There is only one electron in the outer most shell of these metals.  During the formation of ionic bonding with the other elements, these elements ready to lose one electron. 

In comparison to all metals, alkali metals are more ductile, malleable and good conductors of heat and electricity.  The most reactive elements in this group are Cesium and francium.  If alkali metals are exposed to water they can explode.

Colour of alkali metals during flame test:

Metal ion	Flame colour
Lithium	Crimson red
Sodium	Golden yellow
Potassium	Lilac (pale violet)
Rubidium and caesium	Violet

Properties of Most reactive metals in the periodic table (alkali metals):

1. Alkali metals are the light metals.  Their density is low because of larger atomic volumes.
2. Alkali metals have low ionization energies because the last electron is present in the outermost s-orbital and the removal of electron is easy.
3. Due to low ionization energy , alkali metals are highly electropositive.
4. The metallic character of alkali metals increases from lithium to caesium due to low ionization energy.
5. Alkali metals are powerful reducing agents because they have very low reduction potentials.
6. Alkali metals are exposed to air, they tarnish rapidly due to the formation of oxides on the surface.  Hence they are most reactive metals kept under kerosene or paraffin oil and protected from the action of air.

Standard measurement table

Introduction:
In the metric system of measurement, designations of multiples and sub-divisions of any unit may be deduced by combining with the name of the unit the prefixes like deka to, and kilo meaning, respectively, 10, 100, and 1000, and deci, centi, and milli, meaning, respectively, one-tenth, one-hundredth, and one-thousandth.

In scientific usage, it becomes convenient to measure multiples larger than 1000 and subdivisions smaller than one-thousandth. Therefore, the following prefixes have been introduced and these are recognized worlwide:

yotta,   (Y),      meaning 10²⁴            deci,    (d),        meaning 10^-1
zetta,   (Z),       meaning 10²¹            centi,   (c),        meaning 10^-2
exa,     (E),       meaning 10¹⁸            milli,    (m),       meaning 10^-3
peta,   (P),       meaning 10¹⁵            micro, (u),         meaning 10^-6
tera,    (T),       meaning 10¹²            nano,   (n),        meaning 10^-9
giga,   (G),       meaning 10⁹             pico,    (p),         meaning 10^-12
mega, (M),      meaning 10⁶             femto, (f),          meaning 10^-15
kilo,     (k),      meaning 10³             atto,     (a),        meaning 10^-18
hecto,  (h),       meaning 10²             zepto,  (z),        meaning 10^-21
deka,  (da),      meaning 10¹             yocto,  (y),        meaning 10^-24

Units of Length

10 millimeters (mm)  = 1 centimeter (cm)
10 centimeters          = 1 decimeter (dm) = 100 millimeters
10 decimeters           = 1 meter (m)
10 meters                  = 1 dekameter (dam)
10 dekameters          = 1 hectometer (hm)
10 hectometers         = 1 kilometer (km)

Units of Liquid Volume

10 milliliters (mL)       = 1 centiliter (cL)
10 centiliters              = 1 deciliter (dL)
10 deciliters               = 1 liter
10 liters                     = 1 dekaliter (daL)
10 dekaliters             = 1 hectoliter (hL)
10 hectoliters             = 1 kiloliter (kL)

Units of Area

100 square millimeters (mm²)         = 1 square centimeter (cm²)
100 square centimeters                  = 1 square decimeter (dm²)
100 square decimeters                   = 1 square meter (m²)
100 square meters                          = 1 square dekameter (dam²) = 1 are
100 square dekameters                  = 1 square hectometer (hm²) = 1 hectare (ha)
100 square hectometers                 = 1 square kilometer (km²)

Units of Mass

10 milligrams (mg)    = 1 centigram (cg)
10 centigrams           = 1 decigram (dg) = 100 milligrams
10 decigrams            = 1 gram (g)
10 grams                   = 1 dekagram (dag)
10 dekagrams           = 1 hectogram (hg)
10 hectograms          = 1 kilogram (kg)
1000 kilograms         = 1 megagram (Mg) or 1 metric ton(t)

kelvin scale definition

Introduction :
The Kelvin Scale or the absolute scale of temperature – Lord Kelvin devised a scale of temperature which is independent of the thermal property of the working substance. This scale is called Kelvin or absolute scale of temperature. The zero of this scale is the temperature at which the molecular motion ceases and average kinetic energy of molecules becomes zero. This temperature is called absolute zero. It is the lowest attainable temperature. No temperature can be less than this temperature. The temperature on this scale is represented by T and the unit is K i.e. Kelvin.

Relation between Celsius and Kelvin Scale

The size of 1 degree on Kelvin scale is the same as the size of 1 degree on Celsius scae i.e., the difference or change in temperature is the same on both the scales. The ice point 0 degree on the absolute scale is 273K and the steam point 100 degree Celsius is 373K. The absolute zero on this scale is thus corresponds to -273 degree Celsius.

Any temperature t degrees on the Celsius scale is equal to (273 + t) on the Kelvin scale.
And, since 100 Centigrade degrees (ice point is marked as 0 degrees and the steam point is marked as 100 degrees).= 180 Fahrenheit degrees

The relation between Fahrenheit and Kelvin scale is given by the formula,
Kelvin = [(°F-32) / (1.8)] + 273.15

Advantages of using kelvin scale

• If we keep the volume of a sample of gas constant, the pressure of the gas goes up in proportion to the Kelvin temperature. This is automatically holds good for an ideal gas; this is quite fortunate enough that many gases have almost  depict identical behavior, except at very low temperatures. 

•  For standard thermometers, we can change from ordinary mercury thermometers, which are convenient, to a gas thermometer. 

Thus a Kelvin scale is much more beneficial as compared to a Fahrenheit or Celsius scale

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.