CC3abc Atomic Structure Flashcards
What does Dalton’s atomic theory say?
- All matter is made up of tiny particles called atoms
- Atoms cannot be created or destroyed
- The atoms in an element are all identical (but each element has its own type of atom)
What are the subatomic particles of an atom?
Electrons, protons and neutrons
What are the relative charges of the subatomic particles?
Electrons - -1
Protons - +1
Neutrons - 0
What are the relative masses of the subatomic particles?
Electrons - 1
Protons - 1
Neutrons - 1
What do we think an atom actually looks like?
At the centre of all atoms is a tiny nucleus containing protons and neutrons. This is surrounded by fast moving electrons arranged in electron shells at different distances from the nucleus.
Atoms in an element always have an equal amount of protons and electrons and so have no overall charge; the charges cancel out.
Is most of an atoms mass found in the nucleus?
Yes.
Rutherford, in one experiment, tiny positive particles were fired at a thin gold foil. Most of the particles passed straight through, with a few being deflected and a very small number bouncing back.
This suggests that atoms are mostly empty space, with a small positive central nucleus that contains most of the mass.
What is the atomic number?
The number of protons in an atom. The bottom number in an element in the periodic table.
What is the mass number?
The total number of protons and neutrons in an atom. The top number in an element in the periodic table.
What is an isotpe?
A variation of an element that has the same number of protons but different number of neutrons.
What is the relative atomic mass (Ar)?
The mean of mass of an atom element compared with carbon-12.
How to calculate the Ar?
total mass of the atoms (relative mass of element x the weigh, can be in % or g) / the number of atoms, usually 100
