periodicity Flashcards
periodicity
repeating pattern of physical or chemical properties going across the periods
how is atomic radii affected moving left to right across a period?
decreases because the increased number of protons create more positive charge attraction for electrons which are in the same shell with similar shielding
first ionisation energy across a period
general trend is to increase due to increasing proton number as the electrons are being added to the same shell
why is there a small drop between Mg and Al?
Mg has its outer electrons in the 3s sub shell whereas Al is starting to fill the 3p subshell. Al’s electron is slightly easier to remove because the 3p electrons are higher in energy
why is there a small drop between P and S?
S’s outer electron is being paired up with another electron in the same 3p orbital. when the second electron is added to an orbital there is a slightly repulsion between the two negatively charged electrons which makes the second electron easier to remove
why do Na, Mg and Al have high boiling points (increasing)
metallic bonding - strong bonds, gets stronger the more electrons there are in the outer shell that are released to the sea of electrons. a smaller sized ion with a greater positive charge also makes the bonding stronger. higher energy is needed to break metallic bonds.
why does Si have a high boiling point?
macromolecular - many strong covalent bonds between atoms high energy needed to break covalent bonds - very high mp + bp
why do Cl2, S8, P4 have low boiling points?
simple molecular - weak london forces between molecules, so little energy is needed to break them - low mp and bp
why has S8 got a higher melting point than P4
has more electrons (S8 = 128), (P4 = 60) so has stronger london forces between moleucles
why does Ar have the lowest boiling point?
monoatomic - weak london forces between atoms)
