Transcript ATOMIC THEORY “The Quantum Atom”

ATOMIC THEORY
“The Quantum Atom”
These spectra came from excited
gaseous samples of hydrogen.
People a long time ago, believed that the northern lights were a sign from God.
Nobody would believe someone if he were to tell them that it could be explained
with science, and if it was a woman trying to tell them this they would often be
placed in an asylum or they would be placed in the care of one distant relative or
another. Now we know the truth they can be explained by science and Niels
Bohr is just the scientist to do it.
The BALMER SERIES is the visible spectrum series of emission lines for the
hydrogen atom. These lines are the result of electron transitions from:
[n = 3 to shell 2] red, [n = 4 to n = 2] blue green, [n = 5 to n = 2] blue, [n = 6 to n = 2]
violet, all ending in n = 2 energy level. These transitions can be modeled as follows.
Bohr’s revolutionary model of the atom was therefore one with a positive
nucleus and “fixed energy” or quantum orbits for electrons.
For many years people have wondered just what the Northern Lights are .
The Northern Lights or Auroras are, the Creator GodΥs light shows. They fill
people with wonder, have inspired artists and poets, and declared GodΥs
glory and handy work in the sky and firmament above.
More scientific explanations of this phenom enon could not be given until
modern particle physic s was developed and knowledge about the EarthΥs
magnetosphere probed from satellites.
The Sun throws out pa rticles, from its surface, far out into space
calle Solar Winds. Σ These play an impo rtant role in causing the
Northern light s.
What was once hydrog en gas b ecomes a gas o f free electrons
and proton s called plasma. This plasma escapes from the SunΥs
atmosphere through a hol e in the SunΥs magnetic field. As they
escape, th ey are thrown out by the rotation of the sun in a
continuous spi ral like water droplets from a garden-ho se.
Most of the northern lights we see form in the ionosphe re. The energy of
solar wind is converted to vis ible light by a mechanism called a quantum
leap. To explain a quantum leap, imagine a hydrogen atom consisting of a
single positive proton nucleus around which spins a single elec tron at a set
distance. Normally, the elec tron is in an orbit as clo se to the proton as
possible. In a state like this, the hydrogen electron has minimum energy .
There are other possible orbits further away from the nucleus in wh ich the
electron can spin. When a free sub-atomic particle from the solar wind
collides with a hydrogen electron at a high speed, it releases energy.
Because of this, the spinning electron moves into another, higher energy
orbit further out from the nucleus. It now contains more potential
energy, but is unstable and unable to keep this energy. It returns to its
original orbit, releasing the extra energy as a photon of light. Billions of
these quantum leaps that keep occurring create the Northern lights.
CChhaarrggeedd ppaarrttiicclleess iinn ssppaaccee tthhaatt ggeett nneeaarr tthhee EEaarrtthh''ss m
maaggnneettiicc ffiieelldd ccaann ggeett iinn
aanndd ttrraappppeedd.. O
Onnccee tthheeyy aarree ttrraappppeedd,, tthhee ppaarrttiicclleess ssppiirraall ddoow
wnn tthhee m
maaggnneettiicc
ffiieelldd lliinnee ttoow
waarrddss tthhee EEaarrtthh''ss m
maaggnneettiicc ppoolleess.. IItt iiss hheerree aatt tthhee ppoolleess w
whheerree tthhee
ppaarrttiicclleess hhiitt tthhee ggaasseess iinn tthhee EEaarrtthh''ss aattm
moosspphheerree.. TThheessee ccoolllliissiioonnss ggiivvee ooff
eenneerrggyy tthhaatt w
wee sseeee aass ccoolloorreedd lliigghhtt..
The gases in the Earth’s atmosphere determine the auroral lights’ colors. In
the ionosphere, where the collisions are taking place, incoming solar
particles collide with oxygen and nitrogen gases. Oxygen atoms give off
green and red light. Nitrogen atoms give off red light. Some blue and violet
light is also given off, but it is difficult for our eyes to see it.
EARTH'S AURORAS MAKE RARE JOINT APPEARANCE
•
•
Scientists using NASA's Polar spacecraft have
captured the first-ever movie of auroras dancing
simultaneously around both of Earth's polar
regions. During a space weather storm on October
22, Polar's Visible Imaging System observed the
aurora borealis and aurora australis (northern and
southern lights) expanding and brightening in
parallel at opposite ends of the world. The images
confirm the three-century old theory that auroras in
the northern and southern hemispheres are nearly
mirror images -- conjugates - of each other.
"This is the first time that we have seen both auroral
ovals simultaneously with such clarity," says Dr.
Nicola Fox, the science operations manager for the
Polar spacecraft, based at NASA Goddard Space
Flight Center. "With these images, we have the
ability to see the dynamics of conjugate auroras."
FIREWORK
S
COLOUR
•The colour of light we see
depends upon the
wavelengths of the
electromagnetic radiation.
•The visible spectrum
contains red, orange,
yellow, green, blue, and
violet. Low-energy,
longer wavelengths are at
the red end of the
spectrum and Highenergy, shorter ones are at
the violet end.
•All colours together
produce white light.
LIGHT
Light is emitted by:
• Incandescence
• Atomic Emissions
• Molecular Emissions
Incandescence
This kind of light is also known as white light .
• Incandescent light is created when
solid materials are heated to high
temperatures, thus creating light.
• Explosions with gold or white colours
often result from reacting metal shavings
in a high temperature environment.
Atomic & Molecular emissions
These emissions create brilliant colour bursts.
•Atomic Emissions: When light is emitted by atoms of an
element in the gaseous phase each element has unique
colour.
•The high temperature environment that is generated when a shell
explodes causes electrons to jump to higher energy levels in atoms.
•When these “excited” electrons fall back to a lower energy level
they emit light of particular colours or wavelengths.
•Molecular Emissions: can produce similar effects but are
results of molecules instead of elements.
Creating Colour
In order to achieve these different colours,
Pyrotechnicians must add different elements (salts)
to the fireworks.
• Reds
use Strontium and Lithium salts
• Yellows & Oranges use Sodium salts
• Blues & Purples use copper containing
chloride salts, & strontium. These are the most
difficult colours to achieve.
• Greens
use Barium salts
Visible Spectrum
• Brilliant colours that are seen in an emission spectrum are:
• Atomic: When light is emitted by atoms of an element in the
gaseous phase. Each element has unique colour.
– The excited state environment that is generated when either heat or
electric energy causes electrons to jump to higher energy levels in
atoms.
– When these “excited” electrons fall back to a lower energy level they
emit light of particular colours or wavelengths of ‘fixed energy”.
• Bohr’s model of the atom was therefore one with a positive
nucleus and “fixed energy” orbits for electrons.