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| Question | Answer |
| In the currently accepted model of the atom, where are electrons found? | Electrons move around the nucleus in certain regions of the atom called shells or energy levels |
| Complete the sentences: Each shell is given a number called the _____________ ___________ number. The further a shell is from the nucleus, the __________ its energy and the _________ its principle quantum number. | Each shell is given a number called the PRINCIPLE QUANTUM number. The further a shell is from the nucleus, the HIGHER its energy and the LARGER its principle quantum number. |
| Describe the structure of electron shells | Electron shells are divided up into sub-shells. Different shells have different numbers of sub-shells, which each have a different energy. These sub-shells have different numbers of orbitals. |
| Up to how many electrons can one orbital hold? | 2 |
| What are the 4 types of sub-shell? | s p d f |
| How many orbitals are in the s sub-shell (include the maximum number of electrons)? | ORBITALS = 1 MAX ELECTRONS = 2 |
| How many orbitals are in the p sub-shell (include the maximum number of electrons)? | ORBITALS = 3 MAX ELECTRONS = 6 |
| How many orbitals are in the d sub-shell (include the maximum number of electrons)? | ORBITALS = 5 MAX ELECTRONS = 10 |
| How many orbitals are in the f sub-shell (include the maximum number of electrons)? | ORBITALS = 7 MAX ELECTRONS = 14 |
| List the sub-shells in the first shell | 1s |
| List the sub-shells in the 2nd shell | 2s 2p |
| List the sub-shells in the 3rd shell | 3s 3p 3d |
| List the sub-shells in the 4th shell | 4s 4p 4d 4f |
| What is an orbital? | The space that an electron moves in |
| Complete the sentence: Orbitals within the same sub-shell have the same _________. If there are ______ electrons in an orbital, the must have '______' in opposite directions (spin-pairing). | Orbitals within the same sub-shell have the same ENERGY. If there are TWO electrons in an orbital, the must have 'SPIN' in opposite directions (spin-pairing). |
| What is electron configuration? | The number of electrons that an atom or ion has, and how they are arranged |
| What are the 3 ways in which electron configuration can be shown? | Sub-shell notation Electrons in boxes Energy level diagrams |
| Describe the sub-shell notation |
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| Describe the electrons in boxes notation |
One box = one orbital
One arrow = one electron
The up and down arrows represent the electrons spinning in opposite directions
Two electrons can only occupy the same orbital if they have opposite spin
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| Describe the energy levels diagram notation |
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| What are the rules for electron configurations? | 1. Electrons fill up the lowest energy sub-shells first 2. Electrons fill orbitals with the same energy singly before they start sharing 3. The 4s sub-shell has a lower energy level than the 3d sub-shell, so electrons fill the 4s sub-shell first 4. For the configuration of ions from the s and p blocks of the periodic table, just add or remove the electrons to or from the highest energy occupied sub-shell |
| TRUE OR FALSE: When an element is ionised, the electrons are removed from the 3d sub-shell before the 4s sub-shell | FALSE When an element is ionised, the electrons are removed from the 4s sub-shell first rather than the 3d sub-shell |
| Which two elements are the exceptions for the rules of electron configuration? | Chromium Copper |
| Why is copper an exception for the electron configuration rules? |
One of the electrons in the 4s sub-shell has become a part of the 3d sub-shell as a full shell is more stable than a half-filled sub-shell which is more stable than a partially-filled sub-shell (full>half>partial)
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| Why is chromium an exception for the electron configuration rules? |
One of the electrons in the 4s sub-shell has become a part of the 3d sub-shell as a half-filled sub-shell is more stable than a partially-filled sub-shell
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| What are shortened electron configurations? | Noble gas symbols in square brackets (e.g. [Ar]) are sometimes used in electron configurations. For example, calcium can be written as [Ar] 4s² |
| How did the idea of sub-shells and orbital come about? | The Bohr model helped to explain why atoms only absorb or emit energy at certain frequencies. HOWEVER! It doesn't explain some of the finer details of absorption and emission spectra. The model was later refined so that shells did not have to be spherical. |
| Scientists now think of orbitals as an area where electrons are most likely to be, rather than where they will definitely be. Why? | In 1927, Werner Heisenberg came up with the theory that you cannot know the speed of an electron and its exact position at the same time - this is known as Heisenberg's uncertainty principle. |
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