Trends Flashcards
Atomic radii
The size of the atom
Across periods it generally decreases - more protons - tighter atom - except noble gases
Because increasing positive charge (more protons) - attracts electrons more strongly
Noble gases have full shells - outer shell can’t shrink much
Down groups it increases
Because each extra electron shell takes up more space - acts as shield
Valence
The number of outer shell electrons
Across periods it increases
Because more outer shell electrons are added
Down groups it stays the same sort of
Because chemical families share Samar no. of electrons in their outer shell
First ionisation energy
The amount of energy required to remove one electron from an atom (furthest away from nucleus)
Across periods generally increases
Because increasing positive charge - of nucleus attracts and holds electrons more strongly; full shells - harder to remove electrons
Down groups it decreases
Because distance from positive nucleus to furthest electron greets bigger
Successive ionisation energies
Having removed one electron - second electron harder to remove as whole atom becomes more and more positive
Once all outer electrons removed - significantly harder to remove another electron from next shell
Electronegativity
A measure of how strongly atoms attract electrons
Across periods it generally increases; ignore noble gases
Because the increasing positive charge of the nucleus attracts electrons more strongly
Down groups it decreases
Because distance from positive nucleus to outermost electrons gets bigger and shielding decreases the attraction of outermost electrons to the nucleus
Things with low electronegativity
Form positive ions
Oxidise rapidly
React explosively
Be soft, shiny, conductive as elemental solids
Things with high electronegativity
Form negative ions OR
Form covalent bonds
Cause other things to oxidise
Be corrosive as elemental gases
