Atoms Flashcards
What are atoms?
Atoms are incredibly small and cannot be seen without powerful microscopes.
The word “atom” comes from the Greek word meaning “cannot be split.”
All atoms of a particular element are the same, but different elements have different atoms.
What is an atom made of?
Atoms are made of sub-atomic particles:
- Protons
- Neutrons
- Electrons
How are particles arranged in an atom?
Protons and neutrons form the nucleus at the center of the atom.
Electrons move around the nucleus.
What are the properties of the sub-atomic particles?
- Protons
- Positive electrical charge (+).
- Similar in mass to neutrons. - Neutrons
- No electrical charge (neutral).
- Similar in mass to protons. - Electrons
- Negative electrical charge (-).
- Have almost no mass compared to protons and neutrons.
What holds an atom together?
Electrostatic attraction between the positive charge on protons and the negative charge on electrons holds the atom together.
What is the nucleus of an atom?
The nucleus is the dense central part of the atom made up of protons and neutrons.
It is not to be confused with the nucleus of a cell.
Is the atom mostly empty space?
Yes, most of the space in an atom is completely empty.
Which particle has a positive electrical charge?
Protons have a positive electrical charge.
Which of the three particles has the smallest mass?
Electrons have the smallest mass.
Which particles make up the nucleus of an atom?
The nucleus of an atom is made up of protons and neutrons.
What is the overall charge of the helium atom shown in the diagram?
The overall charge of the helium atom is neutral, as the positive and negative charges cancel each other out.
How are individual atoms held together?
Atoms are held together by the electrostatic attraction between the positive charge of protons and the negative charge of electrons.
How did scientists come up with this model of the structure of the atom?
Scientists from around the world contributed ideas that led to the current model of the atom.
In the late 1890s, J.J. Thompson discovered the electron. He proposed the plum pudding model, where electrons are scattered randomly throughout a positively charged matter, like fruit in a pudding.
What is the plum pudding model?
A model proposed by J.J. Thompson:
- Electrons are randomly arranged within a positively charged matter.
- It compares the atom’s structure to a pudding with scattered pieces of fruit.
Who was Ernest Rutherford?
Ernest Rutherford was a scientist from New Zealand. He discovered the proton in 1909 and the nucleus in 1911.
What was Rutherford’s most famous experiment?
The gold foil experiment, where fast-moving particles were fired at very thin gold foil. Most particles passed straight through, but some were deflected (about 1 in 8000). Deflected means the direction of the particles changed.
What did the gold foil experiment reveal?
Atoms are mostly empty space. Most of the atom’s mass is concentrated in a dense nucleus at the center.
How did Rutherford’s model of the atom look?
A dense, positively charged nucleus at the center. Electrons orbit around the nucleus.
Who was James Chadwick?
James Chadwick worked with Rutherford and Thompson. In 1932, he discovered neutrons, moving the model of the atom closer to the one used today.
How do scientists verify discoveries?
Scientists write about their experiments and findings. Other scientists review the work to see if the experiments can be repeated and verified (called peer review). Collaboration often involves scientists from different countries working together.
What is peer review?
A process where other scientists check the experiments and conclusions for accuracy. Mistakes or errors in conclusions are identified and corrected.
How is Thompson’s model different from the current atomic model?
Thompson’s model (Plum Pudding Model): Electrons are scattered randomly in a positively charged mass.
Current model: Electrons orbit a dense, positively charged nucleus.
Who discovered the electron and when?
The electron was discovered by J.J. Thompson in the late 1890s.
Who proved the existence of neutrons and when?
James Chadwick proved the existence of neutrons in 1932.
What two things did Rutherford discover about the atom?
- Atoms are mostly empty space.
- The nucleus is a dense, positively charged center of the atom.
How is Rutherford’s model different from the current model?
Rutherford’s model: A nucleus with electrons orbiting around it.
Current model: More advanced, with specific electron energy levels or shells.
What is the Large Hadron Collider used for?
Scientists use it to further understand the structure of matter and explore what we don’t yet know about atoms.
Why are collaboration and peer review important in science?
Scientists build on each other’s ideas.
Peer review ensures accuracy by repeating experiments and checking conclusions.
