Atomic structure
- Created by: holly6901
- Created on: 28-03-19 16:06
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- Atomic structure
- Developing the model of the atom
- General stuff
- New models change when new evidence is found that can't be explained by the old model
- Scientists used to think atoms were solid balls until they discovered electrons
- This led to the plum pudding model
- The plum pudding model
- The plum pudding model showed the atom as a ball of positive charge with electrons scattered in it
- Later, scientists fired alpha particles at gold foil and proved the plum pudding model wrong
- The nuclear model
- Invented by Neils Bohr
- Electrons go around the nucleus in shells
- Each shell is a fixed distance from the nucleus
- Bohr's theory was proved correct by many experiments
- James Chadwick's experiments proved neutrons exist
- The current model of the atom
- The radius of an atom is about 1x10 to the power of -10
- The nucleus is tiny but takes up most of the mass of the atom
- The radius of the nucleus is 10,000 times smaller than the radius of the atom
- The nucleus is made of protons and neutrons
- Protons are positively charged and neutrons have no time
- Electrons orbit the nucleus at different distances. These distances are called electron shells
- Atoms overall have a neutral charge
- Electrons have more charge, the further away from the nucleus they are. Electrons can move energy shells by absorbing electromagnetic radiation.
- General stuff
- Isotopes
- Atoms of the same element have the same number of protons
- The atomic number shows the number of protons whereas the mass number shows protons+neutrons
- Isotopes are atoms with the same number of protons but a different number of neutrons
- Some isotopes emit radiation from their nuclei to become more stable. This is radioactive decay
- Isotopes that emit radiation are called radioactive isotopes
- Atoms of the same element have the same number of protons
- Untitled
- Types of nuclear radiation
- Alpha
- Strong ionising power
- Range of a few centimetres
- Stopped by a sheet of paper
- Beta
- Moderate ionising power
- Range of a few metres
- Stopped by a sheet of aluminium
- Gamma
- Weak ionising power
- Range of a long distance
- Stopped by a thick sheet of lead or metres of concrete
- Neutrons
- Isotopes can also give out neutrons when they decay
- Ionising radiation turns atoms into ions. The ionising power is how easily types of radiation can do this.
- Alpha
- Nuclear equations
- Nuclear equations are usually written as nucleus before decay-> nucleus after decay + radiation emitted
- The total mass and atomic numbers must be equal on both sides of the arrow
- When a nucleus emits an alpha particle, its atomic number decreases by 2 and its mass number decreases by 4
- In beta decay its atomic number increases by 1 and its mass number stays the same
- In gamma decay, both the atomic number and the mass don't change
- Half-life
- Developing the model of the atom
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