1.6 - the periodic table Flashcards
Who discovered the periodic table?
Mendeelev 1869
left gaps for undiscovered elements
what do the blocks indicate?
the presence of the valence electron
what increases across the period?
ionisation increases across the period
nuclear charge increases across the period
what doesn’t increase across the period?
shielding
As Ionisation increases, atomic radius?
decreases
Between Group 2 and 3?
there’s a decrease in Ionisation ebergy because Group 3’s valance electron is in a new subshell with a higher energy level shielded by the S electrons
Between Group 5 and Group 6?
there’s a decrease in Ionisation energy
there’s a change between N and O
N = singly occupied
O = pair
Difference between singularly occupied orbita anda paired orbital?
easier to remove it
What decreases down the group?
Ionisation decreases
Increase in shielding outweighs the increase in nuclear charge
Electronegativity def?
measure of tendency of an atom to attract a bonding pair of electrons
What increases across a period?
Electronegativity
There is an increase in nuclear charge but the bonding electron is always shielded by the same inner electrons
so there is a greater attraction betweenthe nucleus and the bonding pair
When does electronegativity decrease?
down the group
bonding electrons have increased shielding from nucleus, so attraction between the nucleus and the bonding electrons decrease
Where are the more electronegative elements?
at the top of the RHS
Where are the least electronegative elements?
bottom of LHS
What is the pattern?
there is a general increase from first to 4th electron
a large decrease to the 5th element then a small general decrease to the 8th element
What changes across a period?
the structure of the elements from metallic to giant covalent then to simple molecular
What bonding does Sodium, magnesum, aluminium have?
metallic bonding
increase because metallic bonding gets stronger
metal ions have a greater charge + there is an increased number of delocalised electrons
Silicon?
Giant covalent structure
each atom = bonded covalently to 4 other atoms
a large amount of energy is needed to break all these bonds
Phosphorous, Sulfur+ chlorine?
simple molecular
althought covalent bonds between toms = strong IMF holding these molecules together = weak + dont need much more energy to break
weak vdw
Ar?
lowest melting + boiling temp because it exists as seperate atoms that are held together by induced dipole induced dipole
monoatomic
Trends in melting + boiling temps?
similar in period 2 but boron in Group 3 has a giant covalent non metallic structure
Reduction + Oxidation?
Redox takes place together
Mg + CuO —— MgO + Cu?
Mg has gained oxygen so = oxidised
(increase in oxidation state)
Copper oxide has lost oxygen so = reduced
(decrease in oxidation state)
Shown by?
Mg — Mg2+ + e-
Cu2+ + 2e- —– Cu
Oxidation def?
loss of electrons
Reduction def?
gain of electrons
Mg?
reducing agent and is oxidised in the process
What is another way to tell if a reaction = redox?
to work out the oxidation numbers
E.g Ba+Cl2 —– Bacl2
Oxidation number of Barium decreases from 0 to + 2
therefore have been oxidised
Oxidation number of Chlorine has decreased from 0 to -1 therefore have been reduced
Oxidation number of an atom does not always exchange when it reacts.
It can be helpful to where the oxidation numbers of each atom underneath symbol
2HNO3 + 6 Hi —— 2NO + 3 I2+H20
Nitrogen = reduced, oxidation number decrease from + 5 to + 2
Iodine is oxidised from -1 to 0
Group 1 metals with water ?
Group 1metals react vigorously with cold water to form hydroxide + hydrogen
for example?
2Na(g)+2H2O(l) —— 2 NaOH(aq)+H2(g)
2Li(g)+2H2O(l)—— 2 LIOH(aq) + H2(g)
Reactions increase in vigour as you go down the group
Li floats on water, gently fizzing
Na melts into a ball that dashes around the surface
K melts into a ball + catches on fire
Cs explodes + shatters glass container
Group 2 metals?
reach much less vigorously in fact
Mg reacts very slowly. Again the OH + H = formed
Ca+2H2O—-Ca(OH)2+H2
Reactivity increase as you go down the group e.g?
Ca produces a steady stream of bubbles + liquid goes cloudy as a white ppt of CaOH = Formed
Ba?
produces greater effervesence + solution is clearer since barium Hydroxide = more soluble is colourless
Hydroxides?
more soluble in Group 2
Does magnesium react with water?
cold water no only steam
mg+H2O(g) —MgO+H2
Hydrogen test?
Place a lit splint in an inverted test tube of gas
If it makes a squeaky pop, its H