Energy Levels Flashcards
Describe John Dalton’s atomic model
- known as the hard sphere/billiard ball model
- explained chemical reactions in quantitative terms
- modernised the ideas of element, atom, compound and molecule
Describe J.J. Thomson’s atomic model
- known of the plum pudding model
- discovered that all matter contains tiny negatively charged particles, thus proving the existence of the electron
- a positive sphere of matter with negative electrons embedded in it
Describe Ernest Rutherford’s atomic model
- known as the planetary model
- fired fast-moving alpha particles at very thin gold foil to observe how they were scattered
- disproved the plum pudding model; by showing that the alpha particles (which are positive) would just travel straight through the atom without deflection
- but the experiement showed that some passed through, some were deflected, some were scattered back towards the source
- concluded that the atom is mostly empty space, and that there is a dense, positively charged nucleus at the center of the atom.
What were the conclusions of Rutherford’s model?
- alpha particles had a collision with a heavier particle
- the heavier particle was small, as only a few alpha particles were deflected
- heavy particles must be positive (as the alpha particles were repelled)
- coined the term nucleus, proposing that the positive charge of the atom was in the centre
- nucleus was small but massive compared to electrons and were a large distance from each other
- electrons orbited around the nucleus as if they were at rest and would move straight to the nucleus
What were the faults of Rutherford’s model?
- any accelerating charge will generate electromagnetic radiation (according to Maxwell)
- electrons would consequently radiate energy, slow down and spiral in the nucleus
- this meant that atoms would be unstable
Describe the experiment conducted by Bohr?
- Bohr used the emission lines of the hydrogen spectrum
- Balmer formulated an equation to calculate and therefore predict the wavelengths emitted from hydrogen
- Bohr extended Rutherford’s model and arranged the electrons in concentric spherical shells
- proposed that electrons could only exist stably at only a few specific distances and other radii would be unstable
- Bohr linked the nature of the spectrum of hydrogen to the nature of the electron orbits around the nucleus
- Bohr linked the characteristic wavelengths of light emitted from excited hydrogen atoms to the energy emitted as an electron moved from a higher energy shell to a lower energy shell.
- reasoned that since the energy emitted was discrete never in between there were only stable shells at specific distances from the nucleus.
Why is Bohr’s model useful/unuseful?
- explained the reactivity and chemical bonding of elements
- also explained the emission spectra
- does not give an accurate description of how electrons were distributed in the space around the nucleus as electrons do not circle the nucleus but existed in complex regions, known as electron orbitals
Where do electrons exist?
- in electron orbitals
- we do not know what an electron is at any given time
- we can mathematically determine the volume of space in which it is most likely to be found
- this high-probability region makes up an orbital
Sort in size order from smallest to biggest.
orbital, subshell, shell
What are the features of the s subshell?
single, spherical orbital
What are the features of the p orbital?
three dumbell-shaped orbitals at right angles to each other
What are the features of the d and f orbital?
more complex with five and seven orbitals respectively
What are the benefits of the spdf model?
- provides a more accurate picture of the electron configuration of the atom
- they specify the shape, and positions of the regions of space
How many subshells can a shell have?
equivalent to the shell number
What is the definition of an orbital?
a region of space in which an electron is found
