CC3 Flashcards
What did John Dalton’s atomic theory say?
- All matter is made up of tiny particles called atoms
- Atoms are tiny, hard spheres that cannot be broken down into smaller parts
- Atoms cannot be created or destroyed
- The atoms in an element are all identical (but each element has its own type of atom)
What did JJ Thomson do when investigating atoms?
He investigated the mass of the particles inside cathode rays and found that they were about 1800 times lighter than the lightest atom (hydrogen). Cathode rays, therefore, did not contain atoms but subatomic particles (electrons).
What are atoms made up of?
Electrons, Protons and Neutrons.
What is a Protons relative charge and relative mass?
Relative charge: +1 (positive)
Relative mass: 1
What is an Electrons relative charge and relative mass?
Relative charge: -1 (negative)
Relative mass: 1/1835
What is a Neutrons relative charge and relative mass?
Relative charge: 0 (no charge)
Relative mass: 1
What is the structure of an atom?
At the centre of the atom 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.
Describe the amount of protons and electrons in an atom?
The amount of protons and electrons and always equal in an atom. So, they have no overall charge because the charges cancel out.
What was Rutherfords Gold Foil experiment?
Rutherford did an experiment where he fired tiny positive particles at a thin gold foil. Most of the particles passed straight through the gold foil, with a few being deflected and a very small number bouncing back. Rutherford explained this by suggesting that atoms are mostly empty space, with a small positive central nucleus that contains most of the mass.
Why did the periodic table get rearranged?
The elements in the periodic table used to be placed in order of the masses of their atoms. However, this caused some elements to be grouped with others that had very different properties. Because of this, a few elements were moved around so that elements with similar properties would be grouped together, making the periodic table no longer arranged by mass. As a result, the atomic number was created to correctly order each element.
What is the atomic mass number?
The total amount of protons and neutrons added together.
What is the atomic number?
The total amount of protons only (also represents the amount of electrons only as amount of protons = amount of electrons).
What is an isotope?
Atoms of an element that have the same atomic number (protons) but different mass numbers (protons+neutrons).
How do you differentiate between Isotopes?
You differentiate between Isotopes by adding its mass number to the elements name (e.g. Lithium-6, which has 6 protons and neutrons altogether)
What is nuclear fission?
When the nucleus of a large atom such as uranium, splits into two smaller nuclei.
