Models of the Atom Timeline
Summary
TLDRThis video script traces the evolution of atomic theory from ancient Greek philosophers to modern quantum mechanics. Democritus and Leucippus first proposed indivisible 'atoms', but Aristotle's four elements theory was more accepted. John Dalton's experiments in 1808 confirmed atoms as basic units. JJ Thompson's discovery of electrons led to the 'plum pudding' model, which was later refined by Rutherford's gold foil experiment revealing a concentrated nucleus. Niels Bohr's planetary model was succeeded by Erwin Schrodinger's quantum mechanical model, depicting electrons as probabilistic orbitals. The script concludes by acknowledging the ongoing refinement of atomic models as scientific understanding deepens.
Takeaways
- 📚 The concept of atoms originated from ancient Greek philosophers Democritus and Leucippus, who proposed that all matter was made of uncuttable particles called 'atomos'.
- 🔬 Aristotle's competing theory of matter being composed of earth, water, air, fire, and ether was more popular at the time, overshadowing the atom theory.
- 🧪 John Dalton introduced the first scientific experiments in 1808, suggesting atoms as indivisible and like tiny balls that combine to form different substances.
- 🌐 J.J. Thompson's discovery of electrons challenged Dalton's model, proposing the 'plum pudding model' where electrons are scattered within a positively charged substance.
- 💥 Ernest Rutherford's gold foil experiment revealed a concentrated positive charge at the atom's center, leading to the 'nuclear model' of the atom.
- 🌀 Niels Bohr's model depicted electrons as planets orbiting a sun-like nucleus, a concept that was later refined by quantum mechanics.
- 🚫 Quantum mechanics, particularly through the work of Erwin Schrodinger, showed that electrons do not orbit in fixed paths but form probabilistic 'orbitals'.
- 🔬 Further discoveries by Rutherford and Chadwick identified protons and neutrons as the subatomic particles within the nucleus.
- 🔍 The quantum mechanical model is the most accurate representation of atoms, though it can be complex for simple explanations.
- 🎨 For simplicity, many educational materials use a hybrid model that combines elements of the Bohr and quantum mechanical models to illustrate atomic structure.
- 🔍 As scientific understanding evolves, the models of atoms are subject to change and refinement to more accurately reflect atomic behavior.
Q & A
Who were the first people to discuss the concept of atoms?
-The first people to discuss the concept of atoms were the ancient Greek philosophers Democritus and his teacher, Leucippus.
What did Democritus believe atoms were?
-Democritus believed that atoms were tiny, uncuttable particles that all matter was made of, and that they came in different sizes and shapes.
What was Aristotle's opposing view to Democritus' atomic theory?
-Aristotle proposed that different things were made of different amounts of the elements earth, water, air, fire, and ether, which was an opposing view to Democritus' atomic theory.
Why did people initially not believe in Democritus' atomic theory?
-People initially did not believe in Democritus' atomic theory because it was not supported by experimental evidence, and Aristotle's ideas were more popular at the time.
Who conducted the first scientific experiments that supported the atomic theory?
-The British chemist John Dalton conducted the first scientific experiments that supported the atomic theory in 1808.
How did John Dalton envision atoms?
-John Dalton envisioned atoms as tiny, indivisible balls that arranged in different combinations to make different substances.
What discovery challenged Dalton's view of atoms being indivisible?
-JJ Thompson's discovery of electrons within atoms challenged Dalton's view, showing that atoms were not indivisible but made up of even smaller particles.
What model of the atom did JJ Thompson propose?
-JJ Thompson proposed the plum pudding model of the atom, where electrons were scattered throughout a positively charged substance, like blueberries in a muffin.
What was Ernest Rutherford's discovery regarding the structure of the atom?
-Ernest Rutherford discovered that atoms have a nucleus where all the positive charge is concentrated, and that atoms are mostly empty space with electrons orbiting around the nucleus.
What was Niels Bohr's model of the atom?
-Niels Bohr proposed a model where electrons orbit the nucleus in circular paths, similar to planets around the Sun.
How did Erwin Schrodinger's work differ from Bohr's model of electron orbits?
-Erwin Schrodinger introduced the concept of electron orbitals, which are regions where electrons are likely to be found, rather than fixed circular orbits.
What are the two subatomic particles that make up the nucleus of an atom?
-The two subatomic particles that make up the nucleus of an atom are protons and neutrons.
What is the current understanding of how electrons behave around the nucleus?
-The current understanding is that electrons do not orbit the nucleus in fixed paths but rather move in a way that can be described by quantum mechanics, forming orbitals of various shapes.
Why might the video use a simplified model of the atom for certain explanations?
-The video might use a simplified model of the atom to make it easier to convey fundamental topics and concepts, even though it is not an exact representation of the quantum mechanical model.
Outlines
🔬 Early Theories of Atoms
This paragraph delves into the early conceptions of atoms by ancient Greek philosophers Democritus and Leucippus, who proposed that all matter is composed of indivisible particles called 'atomos'. Democritus envisioned atoms as having different shapes and sizes, with properties like hooks and spikes to explain the behavior of materials like iron and salt. However, these ideas were not widely accepted at the time due to the popularity of Aristotle's competing theory of the four elements. The paragraph also introduces John Dalton in 1808, who conducted the first scientific experiments suggesting matter is made of tiny, indivisible particles, which he called atoms.
🌐 Evolution of Atomic Models
The second paragraph outlines the evolution of atomic models from Dalton's indivisible spheres to more complex structures. It discusses J.J. Thompson's discovery of electrons and his 'plum pudding' model, where electrons were thought to be embedded throughout a positively charged substance. This was later challenged by Ernest Rutherford's gold foil experiment, which revealed a concentrated positive charge in the atom's nucleus, leading to the nuclear model of the atom. Niels Bohr's model introduced the concept of electrons orbiting the nucleus like planets around the Sun, which was later refined by quantum mechanics to describe electrons as occupying probabilistic orbitals rather than fixed paths.
📚 Modern Understanding of Atoms
The final paragraph discusses the current understanding of atomic structure, which includes the quantum mechanical model with its orbitals and the subatomic particles within the nucleus, namely protons and neutrons. It also touches on the practical use of simplified models, like the Bohr model, for teaching and basic explanations of atomic behavior, acknowledging that while these models are not entirely accurate, they serve as useful tools for conveying fundamental concepts in chemistry.
Mindmap
Keywords
💡Atom
💡Democritus
💡Aristotle
💡John Dalton
💡Electron
💡Plum Pudding Model
💡Ernest Rutherford
💡Nuclear Model
💡Niels Bohr
💡Orbitals
💡Quantum Mechanical Model
Highlights
Ancient Greek philosophers Democritus and Leucippus were the first to discuss the concept of atoms, proposing that all matter is made of tiny, indivisible particles called 'atomos'.
Democritus visualized atoms as having different shapes and sizes, with iron atoms having hooks and salt atoms having spikes, based on their physical properties.
Aristotle's opposing theory of matter, composed of earth, water, air, fire, and ether, gained more acceptance due to his popularity.
John Dalton's scientific experiments in 1808 provided the first evidence that matter is made of tiny particles, introducing the atomic theory.
Dalton's atomic model depicted atoms as indivisible, spherical particles, differing from Democritus's model.
J.J. Thomson's discovery of electrons in the late 1800s challenged Dalton's model, suggesting atoms are divisible and composed of smaller particles.
Thomson's 'plum pudding model' proposed atoms as positively charged substances with electrons embedded like blueberries in a muffin.
Ernest Rutherford's gold foil experiment revealed the atomic nucleus, concentrating all positive charge at the center and leaving mostly empty space.
Rutherford's nuclear model contradicted Thomson's, placing a positive charge nucleus at the atom's center with electrons in orbit.
Niels Bohr's 1913 model introduced electron orbits around the nucleus, like planets around the Sun, a significant advancement in atomic theory.
Bohr's model was initially accepted but later challenged by new experimental evidence and quantum mechanics.
Erwin Schrödinger's quantum mechanical model described electrons not as orbiting bodies but as probabilities, forming orbital shapes.
Schrödinger's model introduced the concept of electron orbitals, which are regions of space where electrons are likely to be found.
Rutherford and Chadwick's discoveries of protons and neutrons refined the understanding of the atomic nucleus.
The quantum mechanical model is the current understanding of atoms, with electrons in orbitals and a nucleus of protons and neutrons.
Despite the quantum mechanical model's accuracy, simplified Bohr model representations are often used for ease of understanding in basic atomic discussions.
The evolution of atomic models reflects the ongoing refinement of scientific understanding as new evidence and experiments emerge.
Transcripts
as scientists have done experiments and
learned more and more about atoms
they've changed the way they think about
atoms so in this video we're going to
look at a timeline of the different ways
that scientists have pictured or
imagined atoms over the years now the
first people to really talk about the
idea of atoms were the ancient Greek
philosopher Democritus and his teacher
Leucippus they lived about 2,500 years
ago and Democritus he said something
like this he said imagine you have an
object like say a slice of bread and you
cut that in half and then you take half
of that and you cut it in half and then
you take half of that and you will you
get the idea eventually he said you're
going to come to something that you
can't cut in half anymore and he called
these objects he called them a Hamas
which means uncuttable and it's where we
get the word atom from Democritus
imagined that all matter all stuff was
made of these tiny uncuttable particles
and he imagined that the atoms came in
different sizes and different shapes he
imagined for example that iron atoms had
hooks which is how they could hold
together so strongly and he thought that
salt atoms had spikes on them because he
felt that salt tasted sharp so
Democritus was right but people didn't
really take to his ideas part of the
reason was because around the same time
the well-known philosopher Aristotle
proposed his own idea of what matter was
made of he said that different things
were made of different amounts of the
elements earth water air fire and ether
this is kind of like Captain Planet if
you're old enough to get that reference
and more people believed Aristotle maybe
just because he was so popular already
so Democritus and leucippus they were
right all along but
here's the thing they weren't scientists
they couldn't do experiments in the
laboratory to prove that they were right
and because of this some people think
that their idea it was just kind of a
lucky guess they couldn't actually prove
what they thought so you know how can
you tell whether it's right or wrong
ideas about atoms remain that way for
about 2,000 years until in 1808 the
British chemist John Dalton came up with
the first scientific experiments that
showed that matter was made of tiny
little particles this is kind of how
John Dalton pictured Adams he imagined
them sort of as tiny little balls that
arranged in different combinations to
make different things and he imagined
that these atoms were indivisible you
couldn't cut them into smaller pieces
now at first nobody believed Dalton but
over the course of the 1800s
more and more scientists did begin to
believe what he had to say but then in
the 1900s the early 1900's people's idea
about atoms started to change one of the
key things cause this change was that in
the late 1800s JJ Thompson discovered
that atoms have electrons and he
discovered that electrons are much much
smaller than atoms so while Dalton
thought that atoms were tiny and
indivisible JJ Thompson said no no
they're not indivisible because they're
made up of electrons which are much
smaller
so JJ Thompson pictured the atom as sort
of like a blueberry muffin
he called this the plum pudding model JJ
thompson imagined that if you took an
atom and split it open you'd see tiny
electrons stuck
throughout the inside of it just the way
blueberries are stuck in the dough of a
blueberry muffin and Thompson thought
that what's the dough in a blueberry
muffin that it was like a positively
charged substance so you had negative
electrons stuck in like a positively
charged dough and together the positive
and negative charge balanced the two
things balanced balanced each other out
so that the atom was electrically
neutral but the big change from Dalton's
model to Thompson's model was showing
that atoms weren't actually indivisible
that they were made of even smaller
things now not too much longer in the
gold foil experiment
Ernest Rutherford discovered that Adams
had a nucleus that all the positive
charge in an atom was concentrated right
in its center and that besides that in
the electrons atoms were pretty much
empty space
so JJ Thompson thought the positive
charge was all distributed throughout
like dough in a muffin but Rutherford
showed that all this positive stuff was
concentrated right here in the center
and this is what we call the nuclear
model of the atom because it has a
nucleus sometimes people call this the
Rutherford model now so far we've been
talking a lot about the positive charge
and the nucleus of an atom but we
haven't talked too much about what's
actually going on with these electrons
in the atom in 1913 the physicist Niels
Bohr came up with his model of the atom
he reasoned that there is a nucleus in
the middle just like Rutherford had but
that electrons instead of just sort of
being randomly distributed throughout
the atom Bohr said that the electrons
were sort of like planets around a Sun
that they were spinning around the
nucleus in circular orbits so here a
picture of some of the electrons and
here the orbit
imagine that they're spinning around the
nucleus in these circles all right now
people thought Bohr's idea for the
electrons made a lot of sense at first
but then in the 1920s additional
experiments showed that it wasn't
exactly the way electrons really move
and a variety of physicists particularly
the physicist Erwin Schrodinger showed
that electrons weren't really spinning
in orbits but it's more like they were
hyperactive flies and they were buzzing
around the atom sketching out different
shapes it's kind of if you did like
time-lapse photography on a hyperactive
fly and you saw that over a long period
of time it sketched out a particular
design and whereas Bohr called these
circular paths
he called them orbits Schrodinger called
the hyperactive sketch out shapes
he called them orbitals here's a
circular orbital - but electrons didn't
only make circles this is actually a
sphere because it's a circle in three
dimensions here is another shape another
type of orbital that electrons could
also make looks like this sort of two
teardrops next to each other
so in the quantum mechanical model
electrons don't orbit the nucleus they
buzz around the atom sketching out
different shapes now let's focus on the
nucleus here over the same amount of
time and a little bit later scientists
were discovering the two subatomic
particles that make up the nucleus so we
can refine this picture a little bit
more in 1919
Ernest Rutherford discovered protons
there they are
and then in 1932 James Chadwick
discovered new Tron's so the really
correct view of the quantum mechanical
model shows the orbitals being sketched
out by the electrons but then also show
the subatomic particles protons and
neutrons here in the nucleus now this is
pretty much how we think about atoms
today but as scientists learn more and
more about atoms as they do more
experiments they're going to find that
this model isn't exactly a perfect
representation of what atoms are really
like and they're quite likely to change
this and refine it even more now as I
said this quantum mechanical model is
like the really accurate way to describe
ABS but the thing is with these orbitals
it can really be kind of a pain
sometimes to describe simple things that
atoms are doing using electron orbitals
and so a lot of times in these videos
when I talk about atoms I'm actually
going to be sort of using a cross
between the very correct quantum
mechanical model and the sort of
outdated Bohr model just because for our
purposes a lot of the simple things
we're going to be talking about the Bohr
model it works just fine so already
you've probably seen me draw atoms like
this where you see the the electron
orbits at different angles and sometimes
particularly when we're talking about
bonding we're going to be drawing atoms
like this with the protons and neutrons
here and the nucleus and then electrons
in different rings different orbits on
the outside of the atom we're going to
find that thinking about the atom like
this is very useful for simple tasks
talking about bonding and stuff but keep
in mind that when we're discussing atoms
they actually aren't exactly like this
and they're much more like the quantum
mechanical model so keep in mind that
I'm lying to you a little bit but I'm
lying to you in order to make it easier
to convey some fundamental topics
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