Atoms Flashcards
what defies an element?
its atomic (proton) number
who was the plum pudding model introduced by? and when?
J J Thomson, 1897
who did the gold-foil experiment and what did they hypothethise?
alpha particles could pass straight through the thin foil, or possibly puncture it
what actually happened in the gold foil experiment? (3)
-most of the alpha particles did pass straight through the foil
-a small number of alpha particles were deflected by large angles (> 40°) as they passed through the foil
-a very small number of alpha particles came straight back off the foil
what did Rutherford conclude since the alpha particles went straight through?
an atom is mostly empty space
what did the small number of alpha particles being deflected at large angles suggest?
there is a concentration of positive charge in the atom. (as like charges repel)
what did the very small number of alpha particles coming straight back suggest? (3)
what can you also deduce from this?
the positive charge and mass are concentrated in a tiny volume in the atom (the nucleus)
-chance of being on that exact collision course was very small,
-so ’target‘ being aimed at had to be equally tiny.
who discovered the nuclear atom?
-what did it state?
Ernest Rutherford
- small, positively-charged nucleus surrounded by empty space and then a layer of electrons to form the outside of the atom.
what are isotopes?
atom with the same number of protons but a different number of neutrons to an elementd
what was the bohr atom model?
electrons orbited the nucleus in different energy levels or at specific distances from the nucleus.
what did the bohr atom model explain? (2)
-since particular chemicals burn with certain-coloured flames;
-the pattern of energy released by electrons in the chemical reaction must be the same for every single atom of that element
what can electrons NOT be and be? (ambiguous)
- cannot be arranged at random,
- have fixed levels of energy within each type of atom.
what happens when atoms absorb energy?
electrons at a particular level are pushed up to higher levels
what do electrons emit when jumping back down to a lower level shell?
light of definite frequencies
