chem WA1

redox reaction

e transfer reactions where red and ox occur sim

reduction

gain of e, dec in OS

oxidation

loss of e, inc in OS

reducing agent

substance undergoes ox, loses e, ON on atom inc

oxidising agent

substance undergoes red, gains e, ON on atom dec

ON

no. of e which the atom loses or tends to lose/gains or tends to gain, when it forms the subs

disproportionation

redox reaction whereby atoms of an element in a single subs undergo ox and red sim

common OA

• MnO4-: purple→colourless/brown ppt (acidic/alkaline)

• Cr2O72-: orange→green

• I2: brown→colourless

• Fe3+: pale yellow→pale green

• H2O2

common RA

• S2O32- thiosulfate

• I- iodide

• Fe2+ iron (II)

• H2O2

atomic number

no. of p in nucleus of atom

nucleon number

total no. of p and n in nucleus of atom

isotopes

atoms of same element having same no. of p but diff no. of neutrons (same chem prop)

atomic orbital

region or vol of space near nucleus where there is high probability of finding an e

s orbitals

spherical, non-directional (probability of finding an e at particular dist from nucleus is same in all directions)

p orbitals

dumb-bell shape, directional

d orbital

complex shapes, directional

rules in e arrangement in orbitals

1. e accommodated in orbitals of lowest energy 1st

2. each orbital can only contain max of 2 e of opp spin

3. when filling set of degenerate energy lvls, e enter orbitals singly, w spins in same direction untill set is half-filled b4 pairing takes place

exceptions of rules

1. Cr (1s2 2s2 2p6 3s2 3p6 3d5 4s1)

2. Cu (1s2 2s2 2p6 3s2 3p6 3d10 4s1)

1st IE

min energy required to completely remove 1 mole of v e from 1 mole of ground state atoms in (g) state to form 1 mole of (g) single charged cations

2nd IE

min energy required to completely remove 1 mole of v e from 1 mole of ground-state atoms in (g) state to form 1 mole of (g) doubly charged cations

factors influencing IE

1. nuclear charge

2. screening/shielding effect

3. dist of e from nucleus (no. of e shells)

nuclear charge

• attraction of nucleus for e

• nuclear charge inc w p no.

• greater attraction on v e=greater energy required to remove e

screening/shielding effect

• v e screened/shielded from attraction of nucleus by inner e

• SE inc w no. of e, esp e in inner shells

• greater SE upon v e, lower energy required to remove v e

dist of e from nucleus (no. of e shells)

• e less strongly attracted when further away from nucleus

• further away=lower energy required to remove v e

trend in successive IE

trend: general inc

• as e removed, no. of p unchanged, nuclear charge constant

• SE dec

• remaining e held more strongly, closer to nucleus

• more energy required to remove remaining e

grp trends in IE

trend: down grp, 1st IE dec

• down grp, no. of p inc, nuclear charge inc

• additional e shell, SE inc

• v e further away, less strongly attractrd by nucleus

• less energy required to remove v e, 1st IE dec down grp

period trend in IE

trend: inc across period

• across period, no. of p inc, nuclear charge inc

• additional e added to same shell, SE approx constant

• v e closer and more strongly held by nucleus

• more energy required to remove v e, 1st IE inc across period