No Brain Too Small (PDF)

No Brain Too Small Trends - Across a period, the valence electrons / bonding electrons are found in the same energy level with the same e- - e- repulsion (shielding) from inner energy levels....

No Brain Too Small Trends - Across a period, the valence electrons / bonding electrons are found in the same energy level with the same e- - e- repulsion (shielding) from inner energy levels. HINT: this m is where 1st IE & EN inc, radius dec the thermometer is Q is only nega ve The # of protons increases across a period / nuclear charge increases. This means the electrosta c placed – mass of 1st IE & EN dec, radius inc if the reac on is atrac on between the posi ve nucleus and the valence electrons / bonding electrons increases across Factors – talk water / solu on exothermic a period, and therefore: about the atomic radius decreases. * Nuclear charge more energy is required to remove the outermost valence electrons, so first IE increases. Data must be f * e- - e- repulsion bonding electrons are more strongly atracted to the nucleus, so electronega vity increases. between energy In J Down a group…. valence electron(s) in an energy level further from the nucleus with greater levels repulsion/shielding from inner energy levels. Although # of protons increases down a group, effect is offset by the increasing distance between nucleus and valence electrons. So, electrosta c atrac on between the posi ve nucleus and valence electrons decreases, and therefore: atomic radius increases while 1st ionisa on energy & electronega vity decrease down a group. Electronega vity – ability of an atom in a bond to atract Size of atoms vs ions the (bonding) electrons towards itself. Metal atoms < metal ions as lose 1st Ionisa on energy – the energy to remove one mol of whole energy level. Nonmetal ions > electrons from one mol of atoms in the gaseous state. nonmetal atoms as extra electron(s) in valence shell inc. the e- - e- repulsion. X(g)  X+(g) + e- (where x is symbol for any element) Entropy – the degree of dispersal of energy/mater Shape/polarity Spontaneous means reac on/process just happens (or Around the central atom there are [#] carries on once it starts) e.g. salt dissolves, alcohol burns. regions of electron density. Repulsion To be spontaneous ∆Stotal must be posi ve between these regions of electron density results in a [name] electron ∆Stotal = ∆Ssystem + ∆Ssurroundings geometry to maximise ∆Ssystem is the ‘reac on’ / thing with a  Consider the separa on/minimise repulsion. Since states AND the number of par cles there are [#] bonding regions and [#] ∆Ssurroundings is the surroundings! Need to consider the non-bonding regions the overall enthalpy change ∆H of the system (is it exo or endo?) to molecule/ion shape is [name]. see if surroundings heat up (∆Ssur) / cool down (∆Ssur). ‘X’ is more electronega ve than ‘Y’, so the X-Y bonds are polar / have dipole. Weak intermolecular atrac ons The dipoles are: TD-TD: consider size of molecule = larger molecule = asymmetrically arranged and more electrons = bigger electron cloud = more therefore do not cancel, so _____ is polarisable = more/stronger TD-TD atrac ons. Also a polar molecule. Standard enthalpy of forma on – enthalpy change when 1 mol of substance is formed For IONS – add / subtract electron(s) AND put consider shape of molecule (linear = more/ branched = symmetrically arranged and [ ] brackets around ion and charge outside. less SA for atrac ons to operate over). therefore cancel, so _____ is a non from its elements in their standard states. PD-PD: polar molecules, molecules with overall dipole. polar molecule. Standard enthalpy of combus on enthalpy change when 1 mol of substance is More energy is released Hydrogen bonding: Between molecules with H bonded to forming H2O(l) rather Exo -∆H, Endo +∆H completely burned in oxygen. F, O or N e.g. NH3  but CH3COCH3  than H2O(g) because Relate the weak intermolecular atrac ons to mpt, bpt, ∆fusH X(s)  X(l) ∆vapH X(l)  X(g) Fusion and vaporisa on MORE intermolecular ∆fusH, ∆vapH. Higher values = stronger atrac ons both require bonds to be broken between molecules. Fusion Reactants & products atrac ons are formed – between molecules = more energy needed to be put in to requires some (S to L) but vaporisa on all (L to G), so more in their standard state so reac on is more energy is needed. Bond breaking = endo, bond making = exo. – their state at 25oC exothermic. overcome them!