Chemistry Topic 1 - Atoms Flashcards
What’s the size of an atom?
1 x 10^-10 metres
What’s another phrase for electrons
Energy Levels
Whats the name for number of protons in an atom called?
Proton number or atomic number
Whats the sum of number of protons and neutrons called?
Mass Number
What are the difference in energy of an electrons closer to the nucleus, rather than more distant to the nucleus?
Electron shells closer to the nucleus, house lower energy electrons, rather than electrons further away
What happens to atoms which do not have complete outer electron shells?
They are unstable, and react with other elements to gain/lose electrons to become stable
What were the earliest concepts of atomic theory?
All matter was made of small, indivisible spherical spheres, which became adapted in the 1800s
Who discovered the electron?
JJ Thomson
What model became theorized after the discovery the electron
JJ Thomson, suggested that all atoms were a weakly positive charged spheres, with negative electrons randomly embedded inside like plums in a plum pudding
Who disproved the plum pudding model and with which experiment?
Ernest rutherford had disproved the plum pudding model with the alpha scatter experiment, to which the discovery of the nucleus to which the accepted model became the nuclear model
What did the nuclear model suggest?
Central nucleus which is dense, indivisible and strongly positively charged, with electrons orbiting around it.
Most of the atom is empty space, with the mass of an atom concentrated in the nucleus
What’s the orbital model?
Tiny, dense, indivisible, positive nucleus with electrons orbit in electron shells at fixed distances. The energy of the nucleus are lower in the shells closer to the nucleus
Who disproved the nuclear model?
Niels Bohr’s calculations had disproved the nuclear model, as the electrons would be unstable if they just surrounded the nucleus. His predictions, verified by the experimental data, changed the accepted model to the orbital model
What did rutherford discover in the nucleus?
Nucleus can be divisible into equally charged units, called protons
What was the alpha particle scattering experiment?
Alpha radiation would be emitted by a radioactive material to pass through a really tiny gold foil
What did chadwick discover?
Additional mass of a nucleus can be divided into equal units with no charge called neutrons
What was the expected result of the alpha particle scattering experiment?
The alpha radiation should pass straight through, as the weakly positive atoms wouldn’t have the density to resist the radiation or the charge to reflect the alpha radiation
What did the alpha particle scattering experiment conclude about an atom?
As most alpha radiation passed straight through, there was no charge to reflect or absorb the radiation therefore its empty space
Some radiation was deflected back by another positive charge, and as most the atom is empty space this concludes the radiation is being deflected by a tiny strongly positively charged particle
The radiation is being reflected back to the radioactive material meaning the nucleus is really dense
What are isotopes?
Elements which contain the same number of protons, however a different number of neutrons
Why are the symbols of some elements don’t correlate with its name?
Is derived from the latin or greek names of the element
What determines what an element is?
The atomic number
What is the relative atomic mass of an atom?
Averaged value of atomic mass, which incorporates both the abundance and mass number of all known isotopes
