The distribution of electrons into different shells, sub shells and orbitals of an atom is called its electronic configuration.

The electronic configuration of any orbital can be represented as:  nl^x

n is the number of principal shell, l = symbol of the sub shell or orbital, x= number of electrons present in the orbital

4p¹ means that p- sub shell of the 4th main shell contain one electron.

As we know Germenium Ge has the ground state electron configuration of 1s², 2s², 2p⁶, 3s², 3p⁶, 4s², 3d¹⁰, 4p²

Now in the condition of GeX₂ the two electrons are removed from the p shell,

and in case of GeX₄ the more two electrons are removed from 4s shell because it has low energy than d shell and the rest configuration remains same .

Now according to the question GeX₄ is more stable because it does not have a full valence so it is unfilled valance so GeX₄ is more stable than GeX₂.

On the other hand,

in pbx2 , oxidation state of pb =+2  

and pbx4 , oxidation state of pb =+4  

we know ,

oxidation state of +2 is more stable than +4 . due to inert pair effect.

Boyle’s Law

• Boyle’s law was stated by Robert Boyle.
• It states that at constanttemperature, the pressure of a fixednumber of moles nof gasvaries inversely with its volume.

k₁ = Proportionality constant.

• It depends upon the amount and temperature of gas. It also depends upon the units in which p as well v are expressed.
• Let volume V₁ is occupied at pressure P₁ and temperature T₁.
• Again volume V₂ is occupied at pressure P₂ and temperature T₂. Mathematically, as per Boyle’s law:

P₁ V₁= P₂ V₂ = Constant

P_1/P₂  = V_2/V₁ 

The electrostatic force of attraction which holds the two oppositely charged ions together is called the ionic bond.

Ionic bond and factors affecting it

• It is formed by transfer of electrons.
• It is formed between metal and no metal.
• In it metal always loses electrons and non-metal always accepts electron.

During the formation of methane molecule the carbon atom undergoes sp3 hybridization in the excited state by mixing one 2s and three 2p orbitals to furnish four half filled sp³ hybrid orbitals which are oriented in tetrahedral symmetry in space around the carbon atom. Each of these sp³ hybrid orbitals forms a σsp³-s bond with one hydrogen atom. Thus carbon forms four σsp³-s bonds with four hydrogen atoms.Methane molecule is tetrahedral in shape with 109°28 bond angle.

Ionization Enthalpy of elements is the amount of energy that an isolated gaseous atom requires to lose an electron in its ground state. Losing of electrons results in the formation of cations.

2. Quantum numbers may be defined as a set of 4 numbers with the help of which we can get complete information about all the electrons in an atom ,ie. location ,energy ,the type of Orbital occupied, space and orientation of that orbital.

1. 

postulates of Bohr's model of an atom are:

1. In an atom, the electrons revolve around the nucleus in certain definite circular paths called orbits, or shells.

2. Each shell or orbit corresponds to a definite energy. Therefore, these circular orbits are also known as energy levels or energy shells.

3. The orbits or energy levels are characterized by an integer not, where, n can have values 1, 2, 3, 4……. The integer not (= 1, 2, 3…) is called the quantum number of respective orbit. The orbits are numbered as 1, 2, 3, 4………… etc., starting from the nucleus side. Thus, the orbit for which n=1 is the lowest energy level.

The orbits corresponding to n = 1,2,3,4…..etc., are also designated as K,L,M,N……….etc., shells. When the electron is in the lowest energy level, it is said to be in the ground state.

Since, electronics can be present only in these orbits, hence, these electrons can only have energies corresponding to these energy levels, i.e., electrons in an atom can have only certain permissible energies .

4. The electrons present in an atom can move from a lower energy level (Elower) to a level of higher energy (Ehigher) by absorbing the appropriate energy. Similarly, an electron can jump from a higher energy level (Ehigher) to a lower energy level (Elower) by losing the appropriate energy.

The energy absorbed or lost is equal to the difference between the energies of the two energy levels, i.e.,

ΔE= E (higher) - E (lower)

sp Hybridization

sp hybridization is observed when one s and one p orbital in the same main shell of an atom mix to form two new equivalent orbitals. The new orbitals formed are called sp hybridized orbitals. It forms linear molecules with an angle of 180°

• This type of hybridization involves the mixing of one ‘s’ orbital and one ‘p’ orbital of equal energy to give a new hybrid orbital known as a sp hybridized orbital.
• sp hybridization is also called diagonal hybridization.
• Each sp hybridized orbital has an equal amount of s and p character, i.e., 50% s and p character.

sp³ Hybridization

When one ‘s’ orbital and 3 ‘p’ orbitals belonging to the same shell of an atom mix together to form four new equivalent orbital, the type of hybridization is called a tetrahedral hybridization or sp³. The new orbitals formed are called sp³ hybrid orbitals.

• These are directed towards the four corners of a regular tetrahedron and make an angle of 109°28’ with one another.
•  The angle between the sp3 hybrid orbitals is 109.28⁰
• Each sp³ hybrid orbital has 25% s character and 75% p character.
• Example of sp³ hybridization: ethane (C₂H₆), methane.

An electrolyte is a substance that dissociates in water into charged particles called ions. Positively charged ions are called cations. Negatively charged ions are called anions. Simply, an electrolyte is a substance that can conduct an electric current when melted or dissolved in water.

A molecule is defined as the smallest unit of a compound that contains the chemical properties of the compound. Molecules are made up of groups of atoms. Describing the structure of an atom, an atom is also sub-divided into smaller units. Protons, electrons, and neutrons are sub-particles of an atom. The protons and neutrons are contained inside the nucleus of the atom and electrons revolve around the nucleus.

Protons are positively charged particles whereas electrons are negatively charged particles. Neutrons do not carry any charge. So we can say that the nucleus is positively charged due to the presence of protons. The nucleus is a bulk mass at the centre of an atom. Atoms are largely vacant.

The third law of thermodynamics states that the entropy of a perfect crystal at a temperature of zero Kelvin (absolute zero) is equal to zero.

Entropy, denoted by ‘S’, is a measure of the disorder/randomness in a closed system. It is directly related to the number of microstates (a fixed microscopic state that can be occupied by a system) accessible by the system, i.e. the greater the number of microstates the closed system can occupy, the greater its entropy. The microstate in which the energy of the system is at its minimum is called the ground state of the system.

At a temperature of zero Kelvin, the following phenomena can be observed in a closed system:

• The system does not contain any heat.
• All the atoms and molecules in the system are at their lowest energy points.

Therefore, a system at absolute zero has only one accessible microstate – it’s ground state. As per the third law of thermodynamics, the entropy of such a system is exactly zero.

Isoelectronic species: These are those species which have the same number of electrons.They are the ions of different elements which have same number of electrons but differ from one another in magnitude of nuclear charge.

Examples of isoelectronic species with 10 electrons:N^3-,O^2-,F^-

Diamagnetic means the atoms or molecules  has no unpaired electrons or spins.  Hence, that substance does not get attracted to magnetic field when placed in it.

For example, Cl^-, N₂

Paramagnetic means the atoms or molecules  has one or more unpaired electrons or spins.  Hence, that substance gets attracted to magnetic field when placed in it.

For example, O₂