CBSE Class 11-science Chemistry Structure of Atom
Discovery of Sub-Atomic ParticlesAtomic number is the number of protons which is equal to number of electrons in a neutral atom.
Mass number is the sum of protons and neutrons
Isotopes are the atoms of same element with same atomic number but different mass number.
Planck's Quantum TheoryA Black Body absorbs 100 percent of the radiation that hits it.
When light of appropriate frequency is allowed to fall on a metal, electrons are found to be ejected from the metal surface. This phenomenon is called Photoelectric Effect.
The no. of photoelectrons emitted from a metal is proportional to the intensity of light.
SpectrumAbsorption spectrum is obtained when white light is first passed through the substance and the transmitted light is then analysed in a spectroscope.
Emission spectrum is obtained when radiations emitted by the excited substance are analysed in a spectroscope.
The Emission spectrum of hydrogen consists of large no. of lines appearing in different regions of wavelengths
Dual NatureElectromagnetic radiation possesses dual nature, i.e. particle nature and wave nature.
According to Heisenberg's uncertainty principle it is impossible to determine simultaneously the exact position and exact momentum (or velocity) of an electron.
Electronic Configuration of AtomsThe regions of electron cloud around the nucleus where probability of finding the electron is maximum (say 99 persent) is known as Orbital.
Rules for filling electrons in Orbitals are Aufbau principle, Pauli's Exclusion Principle and Hund's rule.
The extra stability of half-filled and completely-filled electronic configurations is due to 2 factors, a) Exchange energy b) Symmetrical distribution of electrons.
Quantum Mechanical Model of AtomThe orbitals are described by quantum numbers which are defined as a set of four numbers with the help of which complete information about the electrons in an atom can be obtained. The four quantum numbers are Principal quantum number, Azimuthal or magnetic momentum quantum number, Magnetic quantum number and Spin quantum number.
The solution of the Schrodinger wave equation gives us the wave function of the electron and also the probability of finding the electrons in the orbitals.
The regions of zero electron density are called nodes and the plane in which the electron density is zero is called nodal plane.