Atoms Notes
Atoms
It is important to know the history of the atom (not only for the SOL but because it makes our understanding of its development much more important).
The concept of the atom was first credited to a Greek philosopher , in ~440 B.C., named Democritus. He envisioned the atom as small, hard particles that made up all things. The concept was that if anything was broken down to the smallest part that would be a small, hard "uncuttable" particle. The term atom comes from the Greek word "atomos" which means uncuttable/ indivisible.
Next we move to the early 1800's and a gentleman named John Dalton. He did not change the concept of the atoms as being uncuttable as prescribed by Democritus, but added on to that by proposing the Atomic Theory. This theory states that different elements are made up of different atoms, the same element is made up of the same atom and that atoms can combine to form new substances called compound.
In the late 1800's another Englishman named JJ Thomson, through experimenting with an inert gas, concluded that atoms were made of negative particles embedded in a positive matrix. He used a common food of the day to describe it....plum pudding....where the raisins represented the negative part and the pudding the positive matrix. On a more modern note I have changed his concept to a Blueberry Muffin (the blueberries being the negative part and the cake being the positive part).
In the early 1900's Ernest Rutherford, in conducting experiments with radioactive matter "shooting" said particles at a sheet of gold foil, conclusion that atoms were mostly empty space with a dense,positively charged nucleus (containing protons) surrounded by a region in which the negatively charged particles/electrons moved.
Not long afterward Neils Bohr ascertained that the negative particles/electrons were found in fixed levels or shells about the positive nucleus. And he concluded that each shell could only hold so many electrons.
In 1932, Sir James Chadwick discovered that there was another particle in the nucleus that had no charge; he discovered the neutron.
In the 1960's the atom model was further refined in what is called the wave or cloud model. This model states that the electrons, which move at or near the speed of light, move so fast that their effect is a "cloud" appearance. In addition, electrons move between layers depending on their energy state. As electrons gain energy they move to higher levels and as they lose that energy they move back to lower levels.
Not long after this wave model, protons and neutrons were found to contain even smaller particles called "quarks".
It is also important to mention that shortly before Rutherford made his conclusions , Hantaro Nagaoka (in Japan) developed what was known as the Saturn model. In it, the planet represented the nucleus and the rings were the areas where the electrons orbited.
It is important to know the history of the atom (not only for the SOL but because it makes our understanding of its development much more important).
The concept of the atom was first credited to a Greek philosopher , in ~440 B.C., named Democritus. He envisioned the atom as small, hard particles that made up all things. The concept was that if anything was broken down to the smallest part that would be a small, hard "uncuttable" particle. The term atom comes from the Greek word "atomos" which means uncuttable/ indivisible.
Next we move to the early 1800's and a gentleman named John Dalton. He did not change the concept of the atoms as being uncuttable as prescribed by Democritus, but added on to that by proposing the Atomic Theory. This theory states that different elements are made up of different atoms, the same element is made up of the same atom and that atoms can combine to form new substances called compound.
In the late 1800's another Englishman named JJ Thomson, through experimenting with an inert gas, concluded that atoms were made of negative particles embedded in a positive matrix. He used a common food of the day to describe it....plum pudding....where the raisins represented the negative part and the pudding the positive matrix. On a more modern note I have changed his concept to a Blueberry Muffin (the blueberries being the negative part and the cake being the positive part).
In the early 1900's Ernest Rutherford, in conducting experiments with radioactive matter "shooting" said particles at a sheet of gold foil, conclusion that atoms were mostly empty space with a dense,positively charged nucleus (containing protons) surrounded by a region in which the negatively charged particles/electrons moved.
Not long afterward Neils Bohr ascertained that the negative particles/electrons were found in fixed levels or shells about the positive nucleus. And he concluded that each shell could only hold so many electrons.
In 1932, Sir James Chadwick discovered that there was another particle in the nucleus that had no charge; he discovered the neutron.
In the 1960's the atom model was further refined in what is called the wave or cloud model. This model states that the electrons, which move at or near the speed of light, move so fast that their effect is a "cloud" appearance. In addition, electrons move between layers depending on their energy state. As electrons gain energy they move to higher levels and as they lose that energy they move back to lower levels.
Not long after this wave model, protons and neutrons were found to contain even smaller particles called "quarks".
It is also important to mention that shortly before Rutherford made his conclusions , Hantaro Nagaoka (in Japan) developed what was known as the Saturn model. In it, the planet represented the nucleus and the rings were the areas where the electrons orbited.