THE HISTORY OF ATOM THEORY
What Is ATOM ?
ATOM is the smallest constituent unit of ordinary matter
that has the properties of a chemical
element. Every solid, liquid, gas and plasma is composed of neutral or ionized
atoms. Every atom is composed of a nucleus and one or more electrons bound to
the nucleus. The nucleus is made of one
or more protons and typically a smilar number of neutrons.
For
the first atomic theory timeline, the atomic models has change over time, for
atomic models has changed over time. For over two centuries, scientist have
ceated different models o9f the atom. As scientists have learned more and more about
atoms, the atomic model has changed. Atomic Theory Timeline
Here is a timeline of
some of the major ideas
But First, Democritus!
Democritus
was a Greek philosopher (470-380B.C.) who is the father of modern atomic
thought. He proposed that matter could NOT be divided into smaller pieces
forever. He claimed that matter was made of small, hard particles that he
called “atomos”
John
Dalton – 1808
John
Dalton created the very first atomic theory. Dalton viewed atoms as tiny, solid
balls. Dalton was an English school teacher who performed many experiments on
atoms.
His atomic theory had 4 statements…
His atomic theory had 4 statements…
Dalton’s Theory
1. Atoms are tiny, invisible particles.
2. Atoms of one element are all the same.
3. Atoms of different elements are different.
4. Compounds form by combining atoms.
J.J. Thomson (1897)
J.J.
Thomson discovered electrons. He also proposed the existence of a (+) particle His
atomic model was known as the “raisin bun model” He was the first scientist to
show that the atom was made of even smaller things. Thomson’s Model Atoms are
made mostly out of (+) charged material, like dough in a bun. The (-) charged electrons
aren found inside the (+) dough.
Ernest Rutherford (1911)
Rutherford
discovered protons and the nucleus. He showed that atoms have (+) particles in the
center, and are mostly empty space. He called these (+) particles protons. He
called the center of atoms the nucleus. Rutherford’s Experiment Radioactive
material emits beam of (+) alpha particles Screen Gold foil Most particles went
nright through! Strangely, some particles are deflected Rutherford’s Experiment
Gold Nucleus Most α particles went through the gold. The atom is mostly empty
space. Rutherford’s Experiment Some particles deflected and others even bounced
back… this was a crazy! The atom had a very dense (+) center. Rutherford called
it the nucleus.
Niels Bohr (1913)
Niels
Bohr improved on Rutherford’s model. Every atom has a specific number of electron
shells. He proposed that electrons move around the nucleus in specific layers,
or shells.
James Chadwick (1932)
Chadwick
discovered neutrons. He called these particles neutrons. Working with
Rutherford, he discovered particles with no charge. Neutrons are also found in
the nucleus.
The Modern Model (1932-)
Work
done since 1920 has changed the model. It is impossible to know where an electron
is at any given time. The new atomic model has electrons moving around the
nucleus in a cloud. The Current Atomic Model There are Protons Neutrons Electrons
What do you think about history of atom theory?
BalasHapusThe idea that matter is made up of discrete units is a very old idea, appearing in many ancient cultures such as Greece and India. The word "atom" was coined by ancient Greek philosophers. However, these ideas were founded in philosophical and theological reasoning rather than evidence and experimentation. As a result, their views on what atoms look like and how they behave were incorrect. They also could not convince everybody, so atomism was but one of a number of competing theories on the nature of matter. It was not until the 19th century that the idea was embraced and refined by scientists, when the blossoming science of chemistry produced discoveries that only the concept of atoms could explain.
Hapusatoms have a history start democritus, dalton, rufthofh, bohr. chandwick, andthe last is modern models atom
Can you explain disadvantages of J.J Thompson theory ?
BalasHapusAccording to J.J.Thomson’s model, an atom consists of a positively charged sphere with electrons embedded in it. Although this model explained, the main characteristics of the atom at that time but it did not have any experiment support. Therefore, it was opposed by his co-scientists and was rejected. However, his prediction that an atom is electrically neutral and has no net charge is still accepted.
HapusThere are many atomic theories put forward by experts. Which theory is used in chemistry learning in Indonesia?
BalasHapuswe used all atomic theory dalton, jj thomson, rufhfofh, bohr chadwick, and the modern models atom, So we can see the development of atomic theory from time to time to see the comparison
HapusWhat is the weakness of Rutherford theory?
BalasHapusWeakness of Rutherford's Model
HapusThe assumption that the electrons were orbiting around the nucleus was unfortunate. According to the classical electromagnetic theory, if a charged particle accelerates around oppositely charged particles, the former will radiate energy. If an electron radiates energy, its speed will decrease and it will go into spiral motion, finally falling into the nucleus. This does not happen as then the atom would be unstable which it is not. This was the chief weakness of Rutherford’s Atomic Model.
Which theory you think is best? Explain it.
BalasHapusTake anything apart and you'll find something smaller inside. There are engines inside cars, pips inside apples, hearts and lungs inside people, and stuffing inside teddy bears. But what happens if you keep going? If you keep taking things apart, you'll eventually, find that all matter (all the "stuff" that surrounds us) is made from different types of . Living things, for example, are mostly made from the carbon, hydrogen, and oxygen. These are just three of over 100 chemical elements that scientists have discovered. Other elements include metals such as copper, tin, iron and gold, and gases like hydrogen and helium.
HapusI think that all theories about the atom I have explained each have their respective defects and advantages so it can be concluded that each theory has its own advantages and limitations, but in this case the theory of modern atom has perfected all theories about atom
Who is the inventor of modern atom theory?
BalasHapus
HapusA theory of the structure and behavior of atoms has taken more than two millenia to evolve, from the abstract musings of ancient Greek philosophers to the high-tech experiments of modern scientists. However, prior to the scientific revolution and the development of the scientific method starting in the 16th century, ideas about the atom were mainly speculative. It wasn't until the very end of the 19th century that technology became advanced enough to allow scientists a glimpse of the atom's constituent parts: the electron, nucleus, proton, and neutron.
Modern is generally said to begin with John Dalton, an English chemist and meteorologist who in 1808 published a book on the atmosphere and the behavior of gases that was entitled A New System of Chemical Philosophy. Dalton's theory of atoms rested on four basic ideas: chemical elements were composed of atoms; the atoms of an element were identical in weight; the atoms of different elements had different weights; and atoms combined only in small whole-number ratios, such as 1:1, 1:2, 2:1, 2:3, to form compounds.
Not all of these ideas were new; the Greeks had already introduced the idea that elements were composed of atoms and that atoms of different elements had different physical properties. Dalton's particular contribution, which distinguished his work from what had been done before, was his method for actually determining atomic weight. In an essay published in 1805, Dalton had included a list of atomic weights for 21 elements. Dalton was also the first to propose standard symbols for the elements.