Atoms Flashcards
Why has no one ever seen an atom?
Because an atom is too small and moves too rapidly to be seen
Although atoms cannot be seen, how has man gained information about them?
- Spectroscopes
- Field-emission microscopes
- Photographic film
- Geiger counters
What is the purpose of an atomic model?
To summarize all the known facts about atoms in order to explain their behaviour
Who designed the first atomic model and when?
John Dalton - 1808
What charge does this symbol represent? +
Positive
What charge does this symbol represent? -
Negative charge
If two substances attract each other, what does this mean?
This means one has a negative charge while the other has a positive charge. Opposites attract.
If two substances repel each other, what does this mean?
This means the two substances have the same charge, either positive or negative. Same charges repel
In an atom, what do you call a positive charge?
A proton
In an atom, what do you call the negative charge?
An electron
What are the five atomic models?
- Dalton model
- Thomas “plum pudding” model
- Rutherford “planetary” model
- Bohr “orbital” model
- “Wave-mechanical” model (electron cloud)
What is the best atomic model for a physicist?
The wave-mechanical model
What is the best atomic model for a chemist?
The Bohr “oribital” model
What orbits around the nucleus of an atom? What else do they whilst orbit?
Electrons. They also rotate
What does the rotating of electrons whilst orbiting the nucleus cause?
Magentism
The atom’s nucleus contains both what?
Protons and electrons
Why does a neutral atom need to contain an equal number of protons and electrons?
Because they have opposite electrical charges. This balances it.
What takes up most of an atom’s volume?
The orbits of the electrons
Where are most of an atom’s mass contained?
In its nucleus
Why was the neutron discovered much later than the other parts of the atom?
Because a neutron:
1. Carries no charge
2. Usually, it has no effect on other objects
What does the neutron do?
It overcomes the repulsive force of the positive protons and binds the
protone and neutrons together in the nucleus
What determines the isotope an atom exists in?
The number of neutrons in the nucleus of the atom.
What deteremines magnetism?
The direction of the rotation of electrons that revolve around the nucleus
