Developments Leading To The Bohr's Model Of Atom
Chapter Name : Structure Of Atom |
Sub Topic Code : 102_11_02_03_03 |
Topic Name : Developments Leading To The Bohr's Model Of Atom |
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Sub Topic Name : Evidence For The Quantized Electronic Levels: Atomic Spectra |
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Introduction
Every element in nature has a definite signature called atomic spectra. It absorbs some band of electromagnetic radiation and reflects others. The light energy provides energy to atoms which move to unstable states and when return back emit radiation of particular wavenumber.
Pre-Requisites:
Electromagnetic radiation , wave number and different bands of EM radiations
Activity:
Have a look at apple. The apple appears red because it reflects only red light and observe all other lights. Now observe it through green glass. It will appear black as the red color reflected by apple doesn’t pass through green glass and hence appear black.
Real Life Question:
Why does an apple appear red, a guava appear green, a banana appear yellow?
Key Words / FlashCards
| Key Words | Definitions (pref. in our own words) |
|---|---|
| Emission spectrum | It is the spectrum of radiation emitted by a substance that has absorbed energy. |
| Spectral Lines for Atomic Hydrogen | Hydrogen atoms when return from excited state emit energy in different steps. These steps correspond to different wavelengths emitted. Such different lines are grouped together on basis of same ground level. They are lyman, balmer, paschen, bracket and pfund. |
Learning aids / Gadgets
| Gadgets | How it can be used |
|---|---|
| Green transparent glass | To look through. |
| Red apple | To observe. |
Real life uses :
The atomic spectra only allow us to differ things on basis of color. Every color we see is because that material absorbs all other colors and reflects a single color.
Places to visit :
Garden is a great place. see red roses, white lilies, yellow sun flower and think why they appear so.
Practical examples around us
| Examples | Explainations |
|---|---|
| Apple appear red, guavas appear green. | Every material has a particular spectrum. The light energy falling on apple just reflects the red light back and all other colors be it be green, blue or any other colors are absorbed and hence apple appear red. |
What you learn in Theory:
The Electromagnetic radiation falling on material excites the atoms to unstable state. On returning the atom emits radiation of particular wavelength which are signature of the material.
What you learn in Practice:
The different material in nature have a definite signature which we can get using a study of atomic spectra.