Structure of Atom (Part 6)

Bohr's Atomic Theory:

Keeping in view the defects in Rutherford's Atomic Model, Neil Bohr presented another model of atom in 1913.The Quantum Theory of Max Planck was used as foundation for this model. According to Bohr's model, revolving electron in an atom does not absorb or emit energy continuously. The

energy of a revolving electron is 'quantized' as it revolves only in orbits of fixed energy, called 'energy levels' by him.

The Bohr's atomic model was based upon the following postulates:

i. The hydrogen atom consists of a tiny nucleus and electrons are revolving in one of circular orbits of radius ‘r’ around the nucleus.

ii. Each orbit has a fixed energy that is quantized.

iii. As long as electron remains in a particular orbit, it does not radiate or absorb energy. The energy is emitted or absorbed only when an electron jumps from one orbit to another.

iv. When an electron jumps from lower orbit to higher orbit, it absorbs energy and when it jumps from higher orbit to lower orbit it radiates energy. This change in energy, E is given by following Planck's equation.

Where, h is Planck's constant equal to 6.63×10−34 Js, and v is frequency of light.

v. Electron can revolve only in orbits of a fixed angular moment mvr, given as:

Where 'n' is the quantum number or orbit number having values 1,2,3 and so on.

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Relative Atomic Mass

Hello readers! Hope you will be fine. Our today's topic is relative atomic mass. let's start! It is the average mass of the atoms of that element as compared to1/12th the mass of an atom of carbon-12 isotope. Based on carbon-12 as a standard, the mass of an atom of carbon is 12 units and 1/12th of it comes to be 1 unit. When we compare atomic masses of other elements with atomic masses of carbon-12 atom, they are expressed as relative atomic masses of those elements. The unit of relative atomic mass unit is amu (Atomic mass unit). One atomic mass unit is 1/12th the mass of one atom of carbon-12. This was the short intro of Relative atomic mass. See you next with another topic. Thank you!

Structure of Atom(Part 5)

Rutherford's Atomic Model: Rutherford performed 'Gold Foil' experiment to understand how negative and positive charges could coexist in an atom. He bombarded alpha particles on a 0.00004 cm thick gold foil. Alpha particles are emitted by radioactive elements like radium and polonium. These are actually helium nuclei (He2+). They can penetrate through matter to some extent. He observed the effects of α-particles on a photographic plate or a screen coated with zinc sulphide. He proved that the 'plum-pudding' model of the atom was not correct. Observations made by Rutherford were as follows: i.Almost all the particles passed through the foil un-deflected. ii.Out of 20000 particles, only a few were deflected at fairly large angles and very few bounced back on hitting the gold foil. Results of the experiment: Keeping in view the experiment, Rutherford proposed planetary model for an atom and concluded following results: i.Since most of the particles passed through th

Carbon Cycle

CARBON CYCLE: Carbon circulates through the carbon cycle. It shows that carbon may be pres- ent as gaseous atmospheric CO2 constituting a relatively small but highly significant portion of global carbon. Some of the carbon is dissolved in surface water and groundwater as HCO-3 or molecular CO2 (aq). A very large amount of carbon is present in minerals, particularly magnesium and calcium carbonates such as CaCO3. Photosynthesis fixes inorganic C as biological carbon. represented as (CH2O), which is a constituent of all life molecules. Another fraction of carbon is fixed as petroleum and natural gas, with a much larger amount as hydrocarbonaceous kerogen (the organic matter in oil shale), coal, and lignite. Manufacturing processes are used to convert hydro- carbons to xenobiotic compounds with functional groups containing halogens, oxygen, nitrogen, phosphorus, or sulfur. Although a very small amount of total environmental carbon, these com- pounds are particularly significant because of

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