RBSE Class 11 Chemistry Notes Chapter 2 Structure of Atom

These comprehensive RBSE Class 11 Chemistry Notes Chapter 2 Structure of Atom will give a brief overview of all the concepts.

RBSE Class 11 Chemistry Chapter 2 Notes Structure of Atom

→ Dalton’s Atomic Theory: Atom is smallest particle of element which is indivisible and takes part in chemical reaction and contains all properties of that element

→ Cathode Rays: Those rays which produced in discharge tube at very low pressure (10 4 atm) and high voltage (10,000 V) from negative electrode i.e., from cathode.

→ Electron: It is a fundamental particle present in an atom and contains unit negative charge (1.6 × 10^-19 C) and negligible mass(9.0 × 10^-28 g).

→ Anode Rays: These rays produce from positive electrode i.e., anode and contains positive charge. Since without using perforated cathode they can not be produced. So, it is clear that these rays pass from hole of cathode therefore also called as canal rays.

→ Proton: It is elementary particle of atom which posseses unit positive charge (1.67 × 10^-19 C) dnd unit mass (1.6726 × 10^-24 g) which is similar to H-atom

→ Neutron: It is an electrically neutral particle which posseses mass as 1.67493 × 10^-24 g.

→ Atomic number: It is the number of protons present in the nucleus of any element. It is denoted by Z.

→ Mass number: It is the sum of number of protons and neutrons present in nucleus of any atom and denoted by A

 

→ Isotopes: Atoms of element which have same atomic number but different mass number are called isotopes.
For example, ₁H¹, ₁H², ₁H³

→ Isobars: Atoms of different elements having same mass number but different atomic numbers are called isobars.
For example, ¹⁴₆C, ¹⁴₇N

→ Wavelength: It is the distance between the sequential crest or trough of an wave.

→ Amplitude: It is the maximum height of any peak or maximum depth of trough in a wave.

→ Frequency: It is the number of vibration per second in a wave. It is denoted by v.

→ Velocity: It is the distance covered by wave in one second

→ Wave number: It is the number of wavelength in direction of transmission of waves.

→ Electromagnetic wave: When charged particles are accelerated, then alternate electric field and magnetic field are produced, which propogate in the form of wave. These are called electromagnetic waves.

→ Photon: It is the bundle of energy in terms of light.

→ Phonon: It is the quantum of heat energy.

→ Photo-Electric Effect: When light of certain frequency strikes the surface of some metal like K, Cs, Rb etc electrons are ejected. This is called photo-electric effect

→ Threshold frequency: It is characterstic minimum frequency below which photo-electric effect is not observed, is called threshold frequency.

→ Work function: The minimum threshold energy is known as work function (- w₀).

→ Spectra: When a ray of light passed through the prism then it spread out into a series of coloured bonds. It is called spectra

→ Emission spectra: The spectrum formed by electromagnetic radiation emitted by a given source characterstics of the source and the type of excitation including the radiation.

→ Continuous spectra: When seven coloured band of white light are observed as overlapped to each other on photographic plate. It is known as continuous spectra.

→ Heisenberg’s uncertainty principle: It states that, “It is not possible to measure simultaneously both the position and momentum of a microsocopic particle, with absolute accuracy and" certainity”. Mathmatically it is given as
Δx . Δp ≥ \(\frac{h}{4 \pi}\).

→ Quantum number: The four index numbers are used to find out the correct position of electron, energy of electron and nature of electron in external magnetic field in an atom. These numbers are known as quantum numbers.

→ Pauli’s exclusion principle: According to this principle “No two electrons can have same values for all quantum numbers.” Two electrons whose
value of m „ are different (+ \(\frac{1}{2}\) and - \(\frac{1}{2}\)) only can accomodate in same orbital.

→ Orbital: A particular area, which has maximum value of Ψ² and here probability of finding of electrons is greatest.

→ Aufbau’s principle: Electrons are filled in sub-shells in increasing order of energy.

→ Hund’s Rule of maximum multiplicity: According to this rule electrons are filled in degenerate orbitals i.e., orbitals having same energy. Electron pairing will not take place in orbital of same energy until each orbital is singly filled. All unpaired electrons have same spin, then electron with opposite spins are filled

→ Atomic number = No. of protons

→ Mass number (A) = Atomic number (Z) + No. of neutrons (n)

→ Velocity (c) = v . λ

→ Wave number (v̄) = \(\frac{1}{\lambda}=\frac{v}{c}\)

→ Energy of photon ⇒ E = hv = \(\frac{h c}{\lambda}\)
{h = Planck’s constnat= 6.6 × 10^-34 J s)

→ Rydberg’ formula
⇒ (v̄) = \(\frac{1}{\lambda}\) = RH Z²\(\left[\frac{1}{\left(n_1\right)^2}-\frac{1}{\left(n_2\right)^2}\right]\)
R_H = 109677 cm^-1

→ Balmer formula v = \(\frac{1}{\lambda}\) = R_H\(\left[\frac{1}{(2)^2}-\frac{1}{\left(n_2\right)^2}\right]\)cm^-1

→ Angular momentum (mvr) = \(\frac{n h}{2 \pi}\)

→ Energy of Hydrogen electron (E_n) = \(\frac{-1313}{n^2}\)

→ Radius of orbit (r) = \(\frac{n^2 h^2}{4 \pi^2 m Z e^2}\)

→ Radius of ls< orbit (for hydrogen atom) = 0.529Å

→ For nth orbit radius (r) = 0.529n²Å

→ de-Broglie’s Relationship (λ) = \(\frac{h}{m v}=\frac{h}{p}\)

→ Uncertainty principle Δx . Δp ≥ \(\frac{h}{4 \pi}\)

→ Increasing energy order for atomic orbital as per Aufbaus’s principle:
Is < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s < 4f < 5d < 6p < 7s.

→ Mass of electron = 9.1 × 10^-31 kg

→ Mass of proton= 1.675 × 10^-27 kg

→ Mass of neutron= 1.675 × 10^-27 kg

→ Emitted. or absorbed energy in electronic transmition ΔE = E₂ - E₁

→ Number of orbitals in nth shell = n²

→ Number of electrons in nth shell= 2n²