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Description
Flashcards by Jem Kinney, updated more than 1 year ago
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Created by Jem Kinney
almost 10 years ago
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| Question | Answer |
| how are electrons arranged in an atom? | in energy levels around the nucleus |
| Is the electron a particle, a wave or a cloud of charge? | a cloud of charge around the nucleus |
| what is the atomic number? | the number of protons in an atom. |
| what is an isotope? | an atom with the same amount of protons but a different number of neutrons. |
| why do different isotopes of the same element react chemically in exactly the same way? | Because they have the same amount of electrons and it is the electrons that determine the chemical properties of an atom. |
| name a use for radioactive isotopes? | carbon dating |
| what does a mass spectrometer measure? | the mass of separate atoms or molecules in a sample. |
| What are the five main stages in a mass spectrometer? | vaporisation, ionisation, acceleration, deflection and detection. |
| why is the instrument kept under high vacuum? | So the ions don't collide with the air molecules as this could prevent the ions reaching the detector. |
| why is the sample vaporised? | so it can move easily through the mass spectrometer. |
| what happens during ionisation? | a beam of elecrons from an electron gun knock of electrons from the atoms or molecules from the sample to form positive ions. |
| why is the sample ionised? | so the sample has a charge so it can be accelerated and deflected? |
| what happens during acceleration? | the positive ions are attracted by the electric field of negatively charged plates and are accelerated at high speeds. the lower the mass of the the ion the higher the speed it reaches. |
| what happens during deflection? | The beam of ions passes into a magnetic field that deflects the beam of ions into an arc of a circle. The deflection of an ions depends on its mass to charge ration. heavier ions are deflected less than lighter ones and and 2+ ions are deflected twice as much as 1+ ions. |
| how are the ions detected? | The magnetic field is gradually increased so the ions enter the detector one after another. From the strength of the magnetic field where an ion hit the detector a mass to charge ration is worked out on a computer. |
| how do you work out the relative atomic mass of the sample? | you multiple the mass charge ratio of each isotope with its relative abundance, add the results together and divide by the total relative atomic abundance ,unless it is in percentages where you divide by 100. |
| what are doubly charged ions? | ions that lose two electrons during ionisation so they behave like ions with half the mass of a singly charged ion. |
| what is electron spin? | Spin is a property of electrons. Two electron in the same orbital must have opposite spin. |
| what are the three rules for allocating electrons to atomic orbitals? | Atomic orbitals of lower energy are filled first. Atomic orbitals of the same energy fill singly before pairing starts because electrons repel each other. no atomic orbital can hold more than two electrons |
| Why is the 4s orbital filled before the 3d orbital? | Because the 4s orbital is of a lower energy. |
| What is the definition of ionisation energy? | The energy required to remove a mole of electrons from a mole of atoms in the gaseous state. |
| Why is the second ionisation energy of an atom greater than the first? | Because an electron is being removed from a positive ion. |
| why is there a drop in ionisation energy between group 2 and 3? | Because the outer electron in the 3p orbital which is a higher energy level than the 3s orbital and therefore requires less energy to remove. |
| Why is there a drop in ionisation between group 5 and 6? | The drop in ionization energy is due to repulsion between paired electrons which makes it easier to lose an electron. In group 5 electron there is only a single electron occupying each atomic orbital. |
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