History of the Atom C1 Flashcards
What did John Dalton propose about atoms in the early 1800s?
John Dalton described atoms as solid spheres and said that different spheres make up different elements
How did J.J Thomson build onto Dalton’s theory in 1897?
In 1897, J.J Thomson concluded that atoms weren’t solid spheres, his measurements of charge and mass showed that an atom must contain even smaller negatively charged particles - electrons. The solid sphere was changed and the new theory was known as the ‘plum pudding model’.
How did Rutherford prove the Plum Pudding Model wrong in 1909?
In 1909, Ernest Rutherford and his students conducted a gold foil experiment. They fired positively charged alpha particles at an extremely thin sheet of gold. They expected the particles to pass through but some deflected more than expected and a small number deflected backwards. Rutherford came up with a nuclear atom, a tiny positive nucleus in the centre surrounded by a cloud of negative electrons.
What did Niels Bohr find out?
Scientists realised that electrons in a cloud would cause the atom to collapse, so Niels Bohr proposed that electrons were contained in shells. Bohr suggested electrons orbit the nucleus in fixed shells.
What are the subatomic particles an atom is made up of?
An atom is made up of protons neutrons and electrons.
What is the relative mass and relative charge in each subatomic particle?
Particle Relative Mass Relative Charge
Proton 1 +1
Neutron 1 0
Electron 0.0005 -1
How are molecules formed?
Molecules are formed when atoms bond together. They are made up of 2 or more atoms. Molecules can be made up of the same element of different.
What does a mass number show?
A mass number is the total number of protons and neutrons in an atom.
What does the atomic number show?
The atomic number is the number of protons in an atom.
