The Atom Flashcards
Atom definition?
Smallest part of an elements which retains the characteristics of that element.
When did the idea of atoms become a scientific theory?
1808
Dalton’s atomic theory?
1) all matter is made up of atoms
2) all atoms of an element are similar to each other
3) atoms of different elements can combine to form compounds
4) atoms cannot be created or destroyed in chemical reactions
What kind of microscope can be used to see atoms?
Scanning tunnelling microscope
Who discovered the electron and when?
Thomson in 1897
How was the electron discover?
Thomson applied electricity to a glass tube producing cathode rays. The rays were attracted to a positively charged electrode meaning the rays must be negatively charged.
Who proposed the plum pudding model?
Thomson
Explain the plum pudding model?
A random distribution of electrons within a positive cloud.
Who disproved the plum pudding model and when?
Rutherford 1911
How did Rutherford discover the nucleus?
By aiming positively charged particles at a thin sheet of gold. Results showed most carried on straight but occasionally some were deflected meaning atoms must have a small positive centre (nucleus)
Mass and charge of an electron?
1/2000 -1
Mass and charge of a proton
1 +1
Mass and charge of a neutron?
1 0
Atomic mass unit (AMU) definition?
One-twelfth of the mass of carbon 12
What is the atomic number?
The number of protons (also number of electrons in a neutral atom)
