Periodic Table and Radiation Flashcards
What order did scientists use to arrange elements in early periodic tables?
In order of atomic weights
How did Mendeleev overcome the problem of incorrectly placed elements?
Mendeleev did this by leaving spaces for elements that had not been discovered.
How did John Newlands arrange his periodic table?
In order of atomic number
What are the differences between the plum pudding model and the nuclear model?
Plum pudding model: Ball of positive charge with scattered electrons. No nucleus or shells.
Nuclear model: Nucleus that contain protons and neutrons. Shells that contain electrons. Electrons are in fixed positions.
How do you find the number of neutrons or protons in an atom? (Protons and electrons have an equal amount)
Protons are equal to the number at the top (atomic number)
Take that number away from the atomic mass (number at the bottom) to get the number of neutrons
ALPHA RADIATION
- can travel 2-3cm in air
- can be stopped by a sheet of paper
- most ionising (causes the most damage to the body)
- used in smoke detectors
- has a helium nucleus
- has +2 charge
BETA RADIATION
- can travel 1 metre in the air
- can be stopped by a thin layer of aluminium
- mid ionising
- used to measure the thickness of materials
- it has -1 charge (an electron)
GAMMA RADIATION
- can travel in the air forever
- can be stopped by thick lead
- least damaging inside the body
- used to treat cancer and sterilise medical equipment
- it has 0 charge
