Hunkar 2025 Chemistry PDF

# **HUNKAR 2025** ## **English Medium** * **VIDYAKUL** * **Welcome** # **HUNKAR 2025** ## **CHEMISTRY** * **VIDYAKUL** * **GK Sir** # **Chapter 02** ## **Atomic Structure** * **VIDYAKUL** * **TOPIC** * **Towards Quantum Mechanical Model** # **What we will learn today?** * **VIDYAKUL**...

# **HUNKAR 2025** ## **English Medium** * **VIDYAKUL** * **Welcome** # **HUNKAR 2025** ## **CHEMISTRY** * **VIDYAKUL** * **GK Sir** # **Chapter 02** ## **Atomic Structure** * **VIDYAKUL** * **TOPIC** * **Towards Quantum Mechanical Model** # **What we will learn today?** * **VIDYAKUL** * **EMR - Dual** * Wave * Particles * **Electron shell - Stationary shell - Electron** * Emit * Absorb * **EMR - Colour** * Combination of colour - spectrum * **Continuous spectrum** * **Discrete spectrum** * **Line spectrum** # **Dual Nature of Electromagnetic Radiations** * **VIDYAKUL** Plank quantum - EMR - Particle Energy - Wave From the above theory it can be concluded that some properties of light i.e. interference, diffraction can be explained if the light has a wave nature while, some other properties of light like Black Body Radiation & Photoelectric Effect can be explained if light have particle nature thus light have a dual nature. # **Emission and Absorption Spectra** * **VIDYKUL** An instrument used to separate the radiations of different wavelength or frequencies called **spectroscope** which contains prism, which produce Spectra and the study of this spectra is called as **spectroscopy**. This spectra is broadly classified into: 1. **Emission Spectra** 2. **Absorption Spectra.** # **Spectroscope - Instrument** * **VIDYAKUL** * Spectroscope - Instrument - Radiation - Different Wavelength or frequency * Spectroscopy & Prism - Different Wavelength * Glass Slab - Sunlight - 7 Colours - Combination of Different Types of light - Spectrum # **Emission Spectra** * **VIDYAKUL** When radiation passed through prism and then received on the photo graphic plate, the spectrum obtained is "**emission spectrum**." Depending upon the source of radiation emission spectra are of two types: - **Continuous Spectra:** When white light from any process is paused through a prism, it splits into seven different wide bands of colours from violet to red (VIBGYOR) this spectra is so continuous that each band merge into other. It is noted that red colour with the longest wavelength deviates least and vice versa. - **Diagram:** * White light source with a slit * A prism * Visible spectrum: 400nm to 750nm * Violet * Blue * Green * Orange * Red - **Line Spectrum or line spectrum:** When some volatile salt (NaCl) is placed in Bunsen flame light is emitted. The colour of the light emitted depends on the nature of substance ex: Na emits yellow while K emits violet light, when this light is passed the spectroscope it is observed that no continuous spectrum is obtained but some isolated coloured lines are observed on the photographic plate separated from each other by dark spaces this is line spectrum. The spectra of these lines of the elements is termed as finger prints # **Spectroscope - Different Wavelength or different frequency or separated wave** * **VIDYKUL** - **Spectra - Study - Spectroscopy** - **Continuous** - **Emission Spectrum** - **Discontinuous flow** - **Prism** # **Absorption Spectra:** * **VIDYKUL** When white light from any source is passed through a solution or vapours of the substance and then analyzed by the spectroscope, it is observed that some dark lines are seen on the plate, this is due to the absorption of certain light of particular frequency or wavelength is observed in the solution. - These dark spaces are on the same place where colour was observed in continuous spectrum, this can be termed as the photographic negative of the continuous spectrum. The spectrum thus obtained is called as absorption spectrum. - **Diagram:** * Excited sample * Prism * Film or detector * Increasing wavelength * Emission spectrum - **Diagram:** * White light source * Absorbing sample * Prism * Film or detector * Increasing wavelength * Absorption spectrum # **Difference between Absorption and Emission Spectrum** * **VIDYKUL** | **Emission** | **Absorption** | |---|---| | Emission Spectra is obtained when radiation is directly analyzed by source to spectroscope. | Adsorption Spectra is obtained when white light is passed through the substance and then analyzed by the spectroscope. | | It consists of bright coloured lines separated by dark spaces | It consist of dark lines separated by the coloured lines | | It can be continuous or discontinuous | It is always discontinuous | # **Emission Spectrum of Hydrogen** * **VIDYKUL** When hydrogen gas at low pressure is taken in the discharge tube and the light emitted on passing electric discharge is examined with spectroscope the spectrum obtained is called the emission spectrum of hydrogen. It is found that they have a large number of lines which are grouped into different series name after the discoveries. # **Rydberg's Formula** * **VIDYAKUL** Although a large no. of lines are present in hydrogen spectrum, Rydberg in 1980's gave a simple equation for the calculation of wavelengths of these lines. - **Diagram:** * n = ∞ * n =7 * n = 6 * n = 5 * n = 4 * n = 3 * n = 2 * Balmer * H * 4000 A * H * H * 5000 A * H * 6000 A * 7000 A * Paschen * Near infrared * Visible region * n = 1 * Lyman * Ultraviolet * Brackett * Far infrared * Pfund * Far infrared # **Fastrack Revision** * **VIDYAKUL** - Spectroscopy * Spectroscope * Prism * 7 Colours * Spectrum * Conti * Emission * Adsorption * Disconti * Disconti # **Homework** * **VIDYAKUL** - Write the Difference between Emission and Absorption spectrum - Write the short notes on line spectrum # **Next Class** * **VIDYAKUL** - Hydrogen spectrum