Periodic table Flashcards
P What is the periodic law
if you arrange elements in order of increasing atomic number then physical and chemical will repeat in a systematic way that can be predicted
How did Mendeleev arrange elements
in order of increasing atomic mass but left gaps for undiscovered elements
What was discovered after Mendeleev
Noble gases
What is periodicity
Repeating patterns of physical and chemical properties across a period
What is the First ionisation energy
the energy needed to remove 1 mole of electrons from 1 mole of gaseous atoms
What factors affect ionisation energy
shielding
Atomic radius
Nuclear charge
What is shielding
lessening of the pull of the nucleus by inner shells of electrons
what is the general trend in ionisation energies down a group
as you move down a group the i.e decreases because of extra electron shells reducing the attraction for electrons
what is the general trend in ionisation energy across a period
increases because the number of protons increases meaning that the nucleus has a more positive charge so smaller atomic radius and increasing attraction
what is a successive ionisation energy
energy needed to remove 1 electron from each ion in 1 mole of gaseous 1+ ions to form 1 mole of gaseous 2+ ions
What is an alloptrope
different forms of the same element in the same state
What is the structure of graphite
sheets of flat hexagons covalently bonded with 3 bonds each
4th outer electron of each carbon is delocalised
Molecules bonded by weak London forces
What are the properties of graphite
weak forces so sheets can slide over each other
Delocalised electrons conduct electricity
Strong covalent bonds in hexagon sheets -high melting point
What is the structure of diamond
carbon atoms covalently bonded to 4 other carbon atoms in a tetrahedral shape
Why do the boiling points of metals increase across a period
because the metallic bonds get stronger because metal ions have an increasing charge
