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Chemistry AS 2015-16 > deck_4740759 > Flashcards

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What holds electrons and protons together in an atom?

Electrostatic forces of attraction


How do you calculate the mass number?

number of protons + number of neutrons (the total number of nucleons)


Define the term relative atomic mass

The average mass of an atom compared to the mass of 1/12 of a carbon 12 atom


Explain why a time of flight mass spectrometer is kept under a vacuum

To prevent the ions that are produced colliding with molecules from the air


What causes the ions to accelerate through a mass spectrometer?

They are attracted by a negatively charged plate


Give the electronic configuration, showing all the sub levels, of a calcium atom

1s2 2s2 2p6 3s2 3p6 4s2


What is the relative mass of an electron?



What is meant by the term first ionisation energy?

The enthalpy change needed to move an electron from the outer most shell of an atom


Why does the first ionisation energy generally decrease as you go down a group?

Down a group there is more electron shielding because there are increasing numbers of electron shells. Therefore the outer electrons are further from the nucleus and thus easier to remove.


Why does the first ionisation energy generally increase as you go across a period?

As you move across a period, the atomic radius decreases. This means the outer electrons are closer to the nucleus and more strongly attracted to the center. Therefore, it becomes more difficult to remove the outermost electron.