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In 1913, Niels Bohr attempted to resolve the atomic paradox by ignoring classical electromagnetism’s prediction that the orbiting electron in hydrogen would continuously emit light. Instead, he incorporated into the classical mechanics description of the atom Planck’s ideas of quantization and Einstein’s finding that light consists of photons whose energy is proportional to their frequency. Bohr assumed that the electron orbiting the nucleus would not normally emit any radiation (the stationary state hypothesis), but it would emit or absorb a photon if it moved to a different orbit. The energy absorbed or emitted would reflect differences in the orbital energies according to this equation:

Δ E = E f E i = h ν = h c λ

In this equation, h is Planck’s constant and E i and E f are the initial and final orbital energies, respectively. The absolute value of the energy difference is used, since frequencies and wavelengths are always positive. Instead of allowing for continuous values for the angular momentum, energy, and orbit radius, Bohr assumed that only discrete values for these could occur (actually, quantizing any one of these would imply that the other two are also quantized). Bohr’s expression for the quantized energies is:

E n = k n 2 , n = 1 , 2 , 3 ,

In this expression, k is a constant comprising fundamental constants such as the electron mass and charge and Planck’s constant. Inserting the expression for the orbit energies into the equation for Δ E gives

Δ E = k ( 1 n 1 2 1 n 2 2 ) = h c λ

or

1 λ = k h c ( 1 n 1 2 1 n 2 2 )

which is identical to the Rydberg equation for R = k h c . When Bohr calculated his theoretical value for the Rydberg constant, R , and compared it with the experimentally accepted value, he got excellent agreement. Since the Rydberg constant was one of the most precisely measured constants at that time, this level of agreement was astonishing and meant that Bohr’s model was taken seriously, despite the many assumptions that Bohr needed to derive it.

The lowest few energy levels are shown in [link] . One of the fundamental laws of physics is that matter is most stable with the lowest possible energy. Thus, the electron in a hydrogen atom usually moves in the n = 1 orbit, the orbit in which it has the lowest energy. When the electron is in this lowest energy orbit, the atom is said to be in its ground electronic state (or simply ground state). If the atom receives energy from an outside source, it is possible for the electron to move to an orbit with a higher n value and the atom is now in an excited electronic state (or simply an excited state) with a higher energy. When an electron transitions from an excited state (higher energy orbit) to a less excited state, or ground state, the difference in energy is emitted as a photon. Similarly, if a photon is absorbed by an atom, the energy of the photon moves an electron from a lower energy orbit up to a more excited one. We can relate the energy of electrons in atoms to what we learned previously about energy. The law of conservation of energy says that we can neither create nor destroy energy. Thus, if a certain amount of external energy is required to excite an electron from one energy level to another, that same amount of energy will be liberated when the electron returns to its initial state ( [link] ). In effect, an atom can “store” energy by using it to promote an electron to a state with a higher energy and release it when the electron returns to a lower state. The energy can be released as one quantum of energy, as the electron returns to its ground state (say, from n = 5 to n = 1), or it can be released as two or more smaller quanta as the electron falls to an intermediate state, then to the ground state (say, from n = 5 to n = 4, emitting one quantum, then to n = 1, emitting a second quantum).

Questions & Answers

what is the 3d-orbital of Ti³+
Timi Reply
What is Lewis acids
Yabsra Reply
Lewis acid is any substance, such as the H+ ion, that can accept a pair of nonbonding electrons. In other words, a Lewis acid is an electron-pair acceptor. 
betuel
Thanks
Yabsra
🤜🤛
betuel
🤜🤛
betuel
describe the way of seperation of water and kerosene
Tang Reply
Kerosene is a hydrocarbon and non-polar. Water is a polar molecule. So a mixture of both liquids is immicible and by adding them to a separation funnel, you can open the tap flowing the less dense liquid in a container. You can read on bond polarity and separation techniques on Google.
Abdelkarim
kerosene will never with water cos its a immiscible liquid
SUNDAY
what is Chemistry
Papie Reply
Chemistry is a branch of natural light science
Yabsra
10 sentences discussing factors affecting solubility
Sara Reply
why is chemistry a science subject
Ukwumonu Reply
10 sentences discussing factors affecting solubility
Sara
How to name carbonique Atom
lix Reply
how many period do we have in the period table
Joseph Reply
187
Ukwumonu
how do i do ionic equations
Amantle Reply
what is the formula for alkanes
Amantle
CnH2n+2 is the alkane formula.
Walter
whenever you get off your fat arse
then you can start to do some real work
hmm
gabson
How much sodium hydroxide must be dissolved in 100mL of water to prepare a 3.95molL^_1
Cindy
what is vast array
benedict Reply
what is Nanoscience
benedict
from health care to manufacturing. Australian academy of science
what is the compound
Yaasmiin
what is Chemistry
Papie
What is array
Yabsra
what will be the total moles of all the molecule present when the different quantities of following gases are mixed together at step 4g of CH4, 22.4 dm3 of oxygen, 11.2dm3 of carbon dioxide and 3.02×10^23 molecules of ammonia.
Soni Reply
0.5 moles of methane and 0.5 mole of sulfur dioxide are mixed together what will be the mass of mixture. a.20g b.40g c.50g d.55g e.60g
Soni Reply
answer;b
Ravina
thnx
Soni
"the halogens are all oxidizing agents" what is the reason for this observation
Kelvin Reply
they are halogens....that is why numbnut 😁
This is not the place to talk down or be rude. Anonymous User keep your comments to yourself if you can't be more respectful.
Dionne
please what is a lightening thunder?
Onimisi Reply
wat are hydrocarbon s
Opio Reply
I think they are molecules that comprise only of hydrogen and carbon atoms ( they are organic if I'm not mistaken)
Mmathabo
am new here can I join
Yeko
yes u can
Benita
❤️
Ukwumonu
hydrocarbons are compunds of carbon and hydrogen but sometimes the hydrogen are replaced by some other elements like oxgen, ammonia and the hydroxyl groups.........thats what leads to the classification and names of hydrocarbons
SUNDAY
Practice Key Terms 4

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Source:  OpenStax, Chemistry. OpenStax CNX. May 20, 2015 Download for free at http://legacy.cnx.org/content/col11760/1.9
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