C1.5 - R* History of the atom Flashcards
Who were the first to have ideas about particles and atoms?
The first to have ideas about:
1. Particles
2. Atoms
were the ancient Greeks
The ancient Greeks’ ideas become linked to strong experimental evidence in the 1800s, when what?
The ancient Greeks’ ideas become linked to strong experimental evidence in the 1800s, when John Dalton put forward his ideas about atoms
John Dalton’s ideas about atoms in the 1800s:
From his experiments, he suggested what?
From John Dalton’s experiments, he suggested that substances were made up of atoms that were like tiny, hard spheres
What were John Dalton’s ideas about chemical reactions in the 1800s?
John Dalton’s ideas about chemical reactions in the 1800s was that the atoms:
- Rearranged themselves
- Combined with other atoms in new ways
John Dalton’s ideas today are what?
John Dalton’s ideas today are in many ways, still useful
What did a scientist called J.J. Thomson discover?
A scientist called J.J. Thomson discovered the electron
When did J.J. Thomson discover the electron?
J.J. Thomson discovered the electron at the end of the 1800s, in 1897
How did J.J. Thomson discover the electron in 1897
J.J. Thomson discovered the electron in 1897, when he was experimenting by applying high voltages to gases at low pressure
J.J. Thomson discovered the electron in 1897, when he was experimenting by applying high voltages to gases at low pressure, because he did experiments on the beams of particles.
What did Thomson find, from the experiments on the beams of particles?
From the experiments on the beams of particles, Thomson found out that they were attracted to a positive charge
Why did Dalton’s idea that atoms could not be divided or split had to be revised?
Dalton's idea that atoms could not be: 1. Divided Or, 2. Split had to be revised, because these electrons must have come from inside atoms in the tube
After Dalton’s idea that atoms could not be divided or split had to be revised, what did Thomson propose?
After Dalton’s idea that atoms could not be:
1. Divided
Or,
2. Split
had to be revised, Thomson proposed a different model for the atom, the plum pudding model
After Dalton’s idea that atoms could not be divided or split had to be revised, Thomson proposed a different model for the atom - the plum pudding model.
What did Thomson imagine the electrons as?
Thomson imagined the electrons as the bits of plum in a plum pudding
When did the next breakthrough in understanding the atom come, after Thomson’s discovery of electrons?
After Thomson’s discovery of electrons, the next breakthrough in understanding the atom came about 10 years after the new theory for the atomic structure was known as the plum pudding model
What were Geiger and Marsden doing?
Geiger and Marsden were:
- Doing an experiment with radioactive particles
- Firing dense, positively charged particles (alpha particles) at the thinnest piece of gold foil they could make
Geiger and Marsden, in their alpha particle scattering experiments, from the plum pudding model, were expecting what?
Geiger and Marsden, in their alpha particle scattering experiments, from the plum pudding model, were expecting the alpha particles to:
1. Pass straight through the sheet
Or,
2. Be slightly deflected at most
What actually happened in Geiger and Marsden’s alpha particle scattering experiments?
In Geiger and Marsden’s alpha particle scattering experiments, whilst most of the particles did go straight through the gold sheet:
- Some were deflected more than expected
- A small number were deflected backwards
What did Rutherford suggest after Geiger and Marsden’s results for their alpha particle scattering experiments?
After Geiger and Marsden’s results for their alpha particle scattering experiments, Rutherford suggested that Thomson’s atomic model was not possible
What is the nuclear model?
The nuclear model is that there is a tiny, positively charged nucleus at the centre, where most of the mass is concentrated
How does the nuclear model explain the results of Geiger and Marsden’s alpha particle scattering experiments?
The nuclear model explains the results of Geiger and Marsden’s alpha particle scattering experiments, because:
- When alpha particles came near the concentrated, positive charge of the nucleus, they were deflected
- If they were fired directly at the nucleus, they were deflected backwards
- Otherwise, they passed through the empty space
When did the next important development in atomic structure, after electrons and the nucleus come?
After:
1. Electrons
2. The nucleus
,the next important development in atomic structure came in 1914
What did Niels Bohr notice when he revised the atomic model again in 1914?
When Niels Bohr revised the atomic model again in 1914, he noticed that the light given out when atoms were heated only had specific amounts of energy
What did Niels Bohr suggest after what he noticed when he revised the atomic model again in 1914?
After what he noticed when he revised the atomic model again in 1914, Niels Bohr suggested that the:
- Electrons must be orbiting the nucleus at set distances, in certain fixed energy levels (or shells)
- Energy must be given out when excited electrons fall from a high to a low energy level
After what he noticed when he revised the atomic model again in 1914, Niels Bohr suggested that the electrons must be orbiting the nucleus at set distances, in certain fixed energy levels (or shells) and the energy must be given out when excited electrons fall from a high to a low energy level.
What did Bohr match his atomic model to?
Bohr matched his atomic model to the energy values observed
What did scientists realise about the electrons in Rutherford’s atomic model as he described?
About the electrons in Rutherford’s atomic model as he described, scientists realised that them in a ‘cloud’ around the nucleus of an atom would be attracted to the nucleus
What was Bohr’s theory of atomic structure supported by?
Bohr’s theory of atomic structure was supported by many experiments
What did scientists in the early 1900s speculate?
Scientists in the early 1900s speculated that there were 2 types of sub-atomic particles inside the nucleus
What did scientists in the early 1900s have?
Scientists in the early 1900s had evidence of protons
Scientists in the early 1900s speculated that there were 2 types of sub-atomic particles inside the nucleus.
Scientists in the early 1900s had evidence of protons.
Why was it very difficult to detect neutrons in experiments?
It was very difficult to detect neutrons in experiments, because they have no charge
What did further experimentation after Niels Bohr’s theory of atomic structure by Rutherford and other scientists do?
Further experimentation after Niels Bohr’s theory of atomic structure by:
1. Rutherford
2. Other scientists
gave the conclusion that the nucleus could be divided into smaller particles
How were neutrons discovered?
Neutrons were discovered after James Chadwick did an experiment that could only be explained by the existence of neutrons only until 1932
What happened about 20 years after scientists had accepted that atoms have nuclei?
About 20 years after scientists had accepted that atoms have nuclei, James Chadwick carried out an experiment which provided evidence for neutral particles in the nucleus
What did the discovery of neutrons result in?
The discovery of neutrons resulted in a model of the atom which was pretty close to the modern day accepted version
John Dalton’s ideas today are in many ways, still useful.
Example
For example, they help to visualise: 1. Elements 2. Compounds 3. Molecules As well as the: 4. Models still used to describe the different arrangement and movement of particles in solids, liquids and gases
From the experiments on the beams of particles, Thomson found out that they were attracted to a positive charge, showing they must be negatively charged themselves.
What did he call the tiny, negatively charged particles?
Thomson called the:
1. Tiny
2. Negatively charged
particles electrons
Geiger and Marsden, in their alpha particle scattering experiments, from the plum pudding model, were expecting the alpha particles to pass straight through the sheet or be slightly deflected at most.
Why was this?
This was because the positive charge of each atom was thought to be very spread out through the ‘pudding’ of the atom
After Geiger and Marsden’s results for their alpha particle scattering experiments, Rutherford suggested that Thomson’s atomic model was not possible.
The positive charge must be concentrated at a tiny spot in the centre of the atom, because otherwise, the large, positive particles fired at the foil could never be repelled back towards their source.
What did he come up with to explain this new evidence?
Thomson came up with an idea to explain this new evidence, the nuclear model of the atom
After what he noticed when he revised the atomic model again in 1914, Niels Bohr suggested that the electrons must be orbiting the nucleus at set distances, in certain fixed energy levels (or shells) and the energy must be given out when excited electrons fall from a high to a low energy level.
Bohr matched his atomic model to the energy values observed.
What did his nuclear model of the atom suggest?
Thomson’s nuclear model of the atom suggested that all the electrons were contained in shells
Scientists in the early 1900s had evidence of protons but a 2nd sub-atomic particle in the nucleus was also proposed to explain the missing mass that had been noticed in atoms.
What must these neutrons have?
These neutrons must have:
- No charge
- The same mass as a proton
John Dalton’s ideas about atoms in the 1800s:
From John Dalton’s experiments, he suggested that substances were made up of atoms that were like tiny, hard spheres.
He also suggested what?
John Dalton also suggested that each chemical element had its own atoms that differed from others in their mass
John Dalton’s ideas about atoms in the 1800s:
From John Dalton’s experiments, he suggested that substances were made up of atoms that were like tiny, hard spheres.
John Dalton also suggested that each chemical element had its own atoms that differed from others in their mass.
He believed that these atoms could not be what?
John Dalton believed that these atoms could not be:
1. Divided
Or,
2. Split
John Dalton’s ideas about atoms in the 1800s:
From John Dalton’s experiments, he suggested that substances were made up of atoms that were like tiny, hard spheres.
John Dalton also suggested that each chemical element had its own atoms that differed from others in their mass.
John Dalton believed that these atoms could not be divided or split.
They were the what of nature?
They were the fundamental building blocks of nature
A scientist called J.J. Thomson discovered the electron.
The tiny, negatively charged particle was found to have what?
The tiny, negatively charged particle was found to have a mass about 2000 times smaller than the lightest atom
J.J. Thomson discovered the electron in 1897, when he was experimenting by applying high voltages to gases at low pressure, because he did what?
J.J. Thomson discovered the electron in 1897, when he was experimenting by applying high voltages to gases at low pressure, because he did experiments on the beams of particles
J.J. Thomson discovered the electron in 1897, when he was experimenting by applying high voltages to gases at low pressure, because he did experiments on the beams of particles.
From the experiments on the beams of particles, Thomson found out that they were attracted to a positive charge, showing what?
From the experiments on the beams of particles, Thomson found out that they were attracted to a positive charge, showing that they must be negatively charged themselves
After Dalton’s idea that atoms could not be divided or split had to be revised, Thomson proposed a different model for the atom, the plum pudding model.
He said that the tiny negatively charged electrons must be what?
Dalton said that the tiny negatively charged electrons must be embedded in a cloud of positive charge
After Dalton’s idea that atoms could not be divided or split had to be revised, Thomson proposed a different model for the atom, the plum pudding model.
Dalton said that the tiny negatively charged electrons must be embedded in a cloud of positive charge.
He knew that atoms themselves carry no overall charge, so any charges in an atom must what?
Dalton knew that atoms themselves carry no overall charge, so any charges in an atom must balance out
In Geiger and Marsden’s alpha particle scattering experiments, whilst most of the particles did go straight through the gold sheet, some were deflected more than expected and small number were deflected backwards, so what?
In Geiger and Marsden’s alpha particle scattering experiments, whilst most of the particles did go straight through the gold sheet:
1. Some were deflected more than expected
2. A small number were deflected backwards
,so the plum pudding model couldn’t be right
This shocked them
In Geiger and Marsden’s alpha particle scattering experiments, whilst most of the particles did go straight through the gold sheet:
1. Some were deflected more than expected
2. A small number were deflected backwards
,so the plum pudding model couldn’t be right.
This what?
This shocked them
After Geiger and Marsden’s results for their alpha particle scattering experiments, why did Rutherford suggest that Thomson’s atomic model was not possible?
After Geiger and Marsden’s results for their alpha particle scattering experiments, Rutherford suggested that Thomson’s atomic model was not possible, because:
- The positive charge must be concentrated at a tiny spot in the centre of the atom
- Otherwise, the large, positive particles fired at the foil could never be repelled back towards their source
The nuclear model is that there is a tiny, positively charged nucleus at the centre, where most of the mass is concentrated.
What surrounds this nucleus?
A ‘cloud’ of negative electrons surrounds this nucleus
The nuclear model is that there is a tiny, positively charged nucleus at the centre, where most of the mass is concentrated.
A ‘cloud’ of negative electrons surrounds this nucleus, so what?
A ‘cloud’ of negative electrons surrounds this nucleus, so most of the atom is empty space
After electrons and the nucleus, the next important development in atomic structure came in 1914, when what?
After:
1. Electrons
2. The nucleus
,the next important development in atomic structure came in 1914, when Niels Bohr revised the atomic model again
Bohr’s theory of atomic structure supported by many experiments and it helped to explain what?
Bohr’s theory of atomic structure:
- Supported by many experiments
- Helped to explain lots of other scientists’ observations at the time
Scientists in the early 1900s had evidence of protons, but a 2nd sub-atomic particle in the nucleus was also proposed to do what?
Scientists in the early 1900s had evidence of protons, but a 2nd sub-atomic particle in the nucleus was also proposed to explain the missing mass that had been noticed in atoms
About the electrons in Rutherford’s atomic model as he described, scientists realised that them in a ‘cloud’ around the nucleus of an atom would be attracted to the nucleus, causing what?
About the electrons in Rutherford’s atomic model as he described, scientists realised that them in a ‘cloud’ around the nucleus of an atom would be attracted to the nucleus, causing the atom to collapse
Further experimentation after Niels Bohr’s theory of atomic structure by Rutherford and other scientists gave the conclusion that the nucleus could be divided into smaller particles, each of which has what?
Further experimentation after Niels Bohr’s theory of atomic structure by:
1. Rutherford
2. Other scientists
gave the conclusion that the nucleus could be divided into smaller particles, each of which has the same charge as a hydrogen nucleus
About 20 years after scientists had accepted that atoms have nuclei, James Chadwick carried out an experiment which provided evidence for neutral particles in the nucleus.
These became known as what?
These neutral particles in the nucleus became known as neutrons
The discovery of neutrons resulted in a model of the atom which was pretty close to the modern day accepted version, known as what?
The discovery of neutrons resulted in a model of the atom which was pretty close to the modern day accepted version, known as the nuclear model
