Top 10 Most Searched chemistry general terms

 In this post I have show top 10 most searched terms of Chemistry . Let's see what there are.

1. Ionization enthalpy 

It is the amount of energy requires to remove an electron from the outermost shell of an isolated gaseous atom or ion.  

During this process , atom absorb energy and therefore ionization enthalpy is endothermic in nature (absorption of energy takes place). Ionization enthalpy depends on the following factors 

◆Size of an atom or ion

◆nuclear force of attraction

◆Extra stability of half filled or completely filled orbitals

In smaller size atoms , it is difficult to remove electron because the outermost electrons are tightly bounded to the nucleus(strong nuclear force ) . Therefore , it becomes difficult to remove electrons from smaller atoms but at the same time it become easier to remove electron from large sized atoms because the nucleus force acting on those outermost electrons are less and they are loosely bounded or attracted to the nucleus .

Ionization enthalpy decreases down the group due to increase in size doen the group and increases from left to right in a period  due to decrease in size in a period from left to right . 

Examples :

 Ionization enthalpy down the group 

Na > K> Cs

And ionization enthalpy in period 

F > O > C

Third factor is extra stability of half filled or completely filled orbitals .

Nitrogen(1s2 2s2 2p3) has a half filled p-orbital and Oxygen(1s2 2s2 2p4) have no such half filled orbital . Therefore Ionization enthalpy of Nitrogen is more than Oxygen.

2. Electron gain enthalpy

It is the enthalpy Change take place when an electron is added to isolated gaseous atom or ion . 

Electron gain enthalpy can be positive (endothermic) or negative(exothermic ) in nature . It depends whether atom absorbed or released energy. Due to high stability of noble gases , they don't accept electron and hence ionization enthalpy of noble gases are highly positive .

In case of halogens , they have very highly negative electron gain enthalpy because they can easily accept electron and form stable noble gas configuration . Generally , electron gain enthalpy decreases down the group and increases from left to right in period

Examples :

Electron gain enthalpy in group , 

Cl > Br >I

Electron gain enthalpy in period ,

F>O>N>C

3. Electronegative

It is the ability of atom to attract the shared electron pairs towards itself . 

Due to electronegative difference between two atoms in a Molecules , one of the atom which is more electronegative carries partial negative charge whereas other acquire partial positive charge . 

In a periodic table , electronegativity decreases down the group and increases in a period from left to right .

Examples :

Electronegativity in group ,

F>Cl>Br>I

Electronegativity in period ,

F>O>N>C

4. Electron affinity

Electron affinity is defined as the amount of energy release when an electron is added to an atom in gaseous phase . It is always negative (exothermic in nature ) . 

Difference between electron gain enthalpy and electron affinity is that , in electron gain enthalpy  energy can be absorbed or released whereas in case of electron affinity energy is always absorbed . 

5. Valency 

It is the number of electrons in the outermost shell of an atom or 8 minus the number of electrons in the outermost shell of an atom . 

Valency of an atom basically use to determine how man bonds a atom can form by lose , gain or sharing of electrons. Strictly speaking , number of bonds form by an atom is not always equal to its valancy.

6. Chemical Bond 

It is the force of interaction (attraction or repulsion ) between two adjacent atoms in a molecule is called Chemical Bond .

Chemical bonds are of two types : 

◆Covalent bond

◆Ionic Bond

Covalent bond

It is formed by sharing of electrons between two atom having nearly same electronegativity .

 Covalent Bonds are strong and hard in nature . They have high melting point . Diamond is the hardest known Substance . Type of bond present in Diamond is a three dimensional network of Covalent Bonds. They are bad Conductor of electricity except Graphite which is soft and Conduct electricity .

Ionic bond

Ionic bond is formed by loss or gain of electrons between two atoms. This leads to formation of ions. Atom which donated electrons carries positive charge and it is called as cation . Atom which accept electrons carries negative charge and it is called as anion . Ionic bonds are hard and brittle in nature. They also have high melting point . They are bad Conductor of electricity in solid state but good conductor of electricity in molted or aqua phase.

7. Moles

Mole is the number of particles in 12 gram of Carbon(C-12)  . One mole contains 6.022 X 10^23 particles (atoms , ions , molecules) . 

Avogadro's Number = NA = 6.022 X 10^23

Formula for number of moles ,

Number of moles =

Mass of a Substance ÷ molar mass of a Substance

8.  Orbit

Orbit is place or fixed path where electrons revolve around the nucleus without loss of energy. 

Energy is absorbed when an electron is excited from lower energy level to higher energy level . Energy is released when an electron moves from higher energy level to lower energy level .

 Energy of an orbit increase as we move from lower energy level(n=1) to higher energy levels(n=2,3,4,....) .Energy is released in the form of electromagnetic waves. 

9. Orbital

It is the probability of finding an electrons in space .

 s , p, d and f  represents orbitals in an atoms. Different orbitals have different shape , size and orientation . S orbital is spherical in shape and can filled with maximum 2 electrons.p orbital is dumb bell in shape and can filled with maximum 6 electrons . d orbital is double dumb bell in shape and can filled with maximum 10 electrons . f orbital has a diffused shape or we can say that no definite shape . f orbital contains maximum 14 electrons . 

10. Hybridization 

It is the intermixing of atomic orbitals and recasting them into equivalent number of new orbitals having almost same energy and shape .

 By using hybridization ,we are able determine the geometry and shape of different molecules . 

Geometry of a molecule on the basis of hybridization ,

sp -linear

sp2-trigonal planar

sp3- tetrahedral or square planar

sp3d - trigonal bipyramidal

sp3d2-octahedral.