مصادر الكيمياء موقع لتعليم الكيمياء بصورة مبسطة

Ionization energy (or potential) of an element is defined as “The amount of energy required or needed to remove an electron from the neutral gaseous atom to form unipositive ion , for example Na → Na+ + e– + energy This is measured in electron volts per atom or kJ mol-1. For example IE of Na is 495 kJ mol-1. …

Shapes  of s and p orbitals s orbital can have only one possible orientation (as it’s m quantum is zero), it is spherical in shape i.e., in an s orbital the electron distribution is symmetrical around the nucleus in all directions. However the size of s orbital depends on principal quantum number. Large n means large size. Thus 3s orbital …

It states that no electron pairing takes place in the p, d and f orbitals until all the orbitals of the given sub-shell contain 1 electron each with parallel spins.

Pauli’s exclusion principle: No two electrons in an atom can have the same value for the same set of four quantum numbers. Thus if two electrons have identical values of n ℓ and m it follows from this principle that they must differ in their spins i.e., +½ or -½. This means that two electrons can occupy the same sub-level …

Quantum numbers: These are numbers which are used to specify the location and energy of an electron and size, shape and orientation of the orbital to which a particular electron belongs. Principal or total quantum number (n): This quantum number is identical with that used in Bohr Sommer field theory. It can have only non zero positive integral values. i.e. …

De Broglie’s theory of wave nature of electrons: Electron, like light has dual character (particle and wave like) de Broglie suggested the wave nature of electrons and derived the relation λ = h/p where λ is the wavelength and p the momentum of the electron and h is Plank’s constant. This relation is verified by interference and  diffraction experiments with …

Nature of light and electromagnetic spectrum:  According to Newton’s corpuscular theory, light is propagated as a stream of particles, called corpuscles. This could justify the phenomenon of reflection and refraction of light but failed to explain the phenomenon of diffraction, interference etc. Clerk Maxwell suggested that light waves are associated with both electric and magnetic fields, i.e. light may be …

Quantization: means that a quantity does not vary continuously. The energy of an electron in an atom cannot have any arbitrary value but only certain characteristic values. ­A definite quantum of energy is accepted while moving from lower to higher energy level or lost while moving from higher to lower energy level, It does not accept any amount of energy …

Bohr’s model of the atom Neil Bohr in 1913 observed that basic features of Rutherford’s atomic model namely presence of nucleus and revolving electrons were correct but that the electrons revolved round the nucleus in certain allowed circular orbits and that the electrons did not radiate and therefore its energy remained constant. However, the electron could jump from outer stationary …

Rutherford model of atom Rutherford observed that atom has all the positive charge concentrated in a very small central region called the nucleus and that nucleus is surrounded by negatively charged particles called electrons revolving in orbits. He proved that the force of attraction between electrons and nucleus was counter balanced by the centrifugal force acting on the revolving electron. …