ATOMIC STRUCTURE ANALOGIES
… from Science Analogies.Info
- Atomic Size is like the Growth Rings of a Tree
- Atomic Size is like the Spots on a Giraffe’s Neck
- Energy Levels are like Rows in a Parking Lot
- Energy Levels are like Standing on a Ladder
- Energy Levels are like a Stick Shift
- Photoelectric Effect is like Shooting with Different Guns
- Photons are like Backpacks
- Wave Mechanical Model is like a Power Boat
- Wave Particle Duality is like Watching a TV Screen
Atomic Size is like the Growth Rings of a Tree
As you go down a vertical group in the periodic table, the trend is
that the atomic radius increases as more energy levels are added on.
This is similar to the observation that as a tree adds on growth rings,
the stem becomes larger in radius.
Source: Original
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Atomic Size is like the Spots on a Giraffe’s Neck
The increasing atomic size as you go down a vertical group or
family in the periodic table is similar to the pattern of increasing
size shown by the spots on a giraffe’s neck as you go from its head down
to the body.
Source: Original
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Energy Levels are like Rows in a Parking Lot
Parking lot rows are analogous to the energy levels in an atom in the following ways:
Different numbers of electrons are found in different energy
levels. Similarly, not all rows will hold the same number of cars,
depending on the location and shape of the rows.
The energy levels, generally speaking, fill from the nucleus
outwards. Similarly, the arena in which the basketball or hockey game is
being played, represents the nucleus of the atom. The parking lot rows
that are closest to the arena are always the ones which get filled up
first, and the farther away ones later.
The ionization energy of an electron in an outside energy level is
smaller than for an electron in an inner level. Similarly, a car parked
on an outer row of the parking lot can generally get out of the lot
easier after the event, than a car located in one of the congested inner
rows, closer to the arena (nucleus).
Source: Original
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Energy Levels are like Standing on a Ladder
One of the main postulates of the Bohr Model of the atom is that
electrons can only exist in certain stable energy levels. It is
analogous to saying that when you stand on a ladder you have a certain
amount of potential energy at each rung position, and you can not stand
at any in betwen position or have any in between amount of energy. If
you do try to stand at a position in between two rungs, you will always
automatically slide down to a lower rung and a correspondingly lower
energy position.
Source: Original
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Energy Levels are like a Stick Shift
According to the Bohr Model, electrons can only exist in particular
energy levels around the nucleus. This is like a stick shift on an
automobile … it only works when it is in 1st gear, 2nd gear, etc … and
not at any in between position.
Source: Unknown
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Photoelectric Effect is like Shooting with Different Guns
When a beam of low frequency, low energy light is directed onto a
metal surface, it will reflect off with no effect upon the metal. If
many light sources of the same frequency are used, there is still no
effect on the metal. An analogy would be that if you shoot at a person
in a suit of armor using either a single BB gun or many BB guns at once,
the person inside the armor will not be affected.
If light of higher frequency and energy from only a single source
is used, then this greater amount of energy may be absorbed and cause
electrons to be promoted and ejected. Similarly, if the BB gun is
replaced by a more powerful rifle, then it would only take one shot to
pierce the armor and hurt the person inside.
Source: McCullough, Thomas Simple Analogies in General Chemistry Journal of Chemical Education July 1992, 69(7), 543.
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Photons are like Backpacks
According to the Quantum Theory, an electromagnetic wave guides a
flow of energy which is transported along the wave in bundles (photons)
of size hf. A simplified view of the situation would be to say that if a
wave was represented by a group of people marching in a line, the
photons would be analogous to the backpack each person was wearing, and
each of which contained a particular amount of material. This analogy
could be extended to say that older, more energetic adults would carry a
greater load in their backpacks than would children.
Source: Original
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Wave Mechanical Model is like a Power Boat
When a power boat is cruising on a lake, the wave which it produces
has its greatest amplitude right at the boat, and the amplitude
decreases as the distance from the boat increases. Thus you could locate
the most probable location of the boat by analyzing the amplitude and
energy of its associated water wave.
This is analogous to the wave mechanical model which visualizes the
atom as a positive nucleus surrounded by vibrating electron waves. The
Schroedinger Wave Equation describes the amplitude and other
characteristocs of the waves which are associated with the moving
electrons, and thus it also is able to describe the energy and location
of the orbiting electrons.
Source: Original
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Wave Particle Duality is like Watching a TV Screen
Sometimes electrons are described as being small particles of
matter. At other times when we describe the organization and behavior of
electrons, we treat them as wave patterns.
Someone who had never seen a television would report seeing
recognizable images of people, buildings, etc. when watching the screen
from across the room. However, a similar observer, if placed with their
eye right up against the screen, would report seeing dots of varying
colors and brightness. Both descriptions of the screen are correct; the
perspective of the viewer determines which properties are observed at
that moment.
Source: Licata, Kenneth P. Chemistry Is Like a … Science Teacher 1988, 55(8), p.42
CHEMICAL BONDING ANALOGIES
… from Science Analogies.Info
- Coordinate Covalent Bonding is like Borrowing Library Books
- Covalent Bond Types are like Eating in a Restaurant
- Resonance Hybrid is like a Mule
Coordinate Covalent Bonding is like Borrowing Library Books
Coordinate covalent or dative bonding is often described in a
simple fashion by saying that it involves one atom donating or giving a
pair of electrons to another, so that this bonding partner can have a
full outer shell. When electrons are counted up in an electronic dot
diagram, this coordinate covalent pair is counted with each of the
atoms. It is similar to borrowing a pair of books from the public
library … the books are given to you and you treat them essentially as
if they belonged to you; yet at the same time the books are counted as
being part of the library collection.
Source: Original
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Covalent Bond Types are like Eating in a Restaurant
A nonpolar covalent bond forms when electrons are shared equally
between atoms. A polar covalent bond forms when electrons are not shared
equally … the more electronegative atom “gets” more electrons than he
gives away by sharing. A coordinate covalent bond is imagined to form
when one atom donates the entire pair of electrons which are shared with
the other atom.
A restaurant analogy for these situations could be as follows:
A nonpolar covalent bond is formed if you give your friend half of
your cheeseburger in exchange for half of his chicken burger. A polar
covalent bond would be like your friend taking all of your cheeseburger
and in exchange giving you just a small bite of his chicken burger. A
coordinate covalent bond forms if you notice a homeless person outside,
bring them into the restaurant, and give them your whole dinner to eat.
Source: Original
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Resonance Hybrid is like a Mule
The actual electronic structure of a molecule or ion which involves
resonance is often explained by saying that it is the average of
several contributing electronic structures which are drawn so as to show
the double bond in several different locations in the species. In order
to remind students that the actual resonance hybrid structure doesn’t
alternate from one contributing structure to another from time to time,
but rather has its own special structure all the time, it is convenient
to use the analogy that a resonance hybrid is like a mule . When you
look at a mule ( which is a cross between a horse and a donkey) you
don’t see a donkey at one time and a horse at another… you see a mule at
all times.
Source: Sienko, M. J. and Plane, R. A. Chemistry Toronto: McGraw-Hill, 1964 p.94
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