Chemistry for Biologists (CHU11101)

C-12, 6

12= mass number (protons + neutrons), and 6 = atomic number (protons=electrons)

Alkalimetals

group 1, not found in elemental state in nature, melt at low temperature, reactivity increases down the group, single electron in outermost shell

Alkaline earth metals

group 2, often found in nature as oxides, two electrons in outermost shell

Halogens

group 17, very reactive

Noble gasses

group 18, colourless and odorless gasses, full outershell, unreactive

Atomic orbitals

s (2, 1 sphere),p (6, 3 dumbells),d (10, 5 complicated shapes),f (14); each can hold 2 electrons that must have opposite spin, will pair singly before pairing up.

Atomic radius

decreases across the table (the more electrons the smaller the atom because of magnetic forces), increases down the table (the more shells the bigger the atom)

Ionic radius

decreases across the table (metals lose electrons and become smaller, non-metals gain electrons and become bigger), and increases down the table.

Electronegativity (=ability for an atom to attract electrons)

Electronegativity increases across the table (right of table tends to gain electrons, left of table tend to lose electrons (valence shells less than half full)), decreases down the table (increase in energy levels, weakens nuclear attraction)

Ionisation energy (= energy to remove one electron from the outer-shell)

increases across the table (bc high for electronegative elements and noble gasses), decreases down the table (low for elements with high n of energy levels).

Hybridisation

Mixing of atomic orbitals to produce an equivalent number of hymbrid orbitals that are more favourable for bonding. Sigma bond = single bond of sp3 orbitals between two atoms, contains two electrons. Pi-bond = hybrid bond of sp2 orbitals between 2 c-atoms.

Alfa decay

helium nucleus ejected: 4 2 He, high ionisation ability, small penetration

Beta decay

neutron converted to proton and 0 -1 e ejected, medium ionisation ability, medium penetration (positron: 0 1 beta)

Gamma decay

high energy photons are released, low ionisation ability, high penetration

Electron capture

0 -1 electron + 1 1 proton → 1 0 neutron

Bonding

nonpolar (0.0-0.4), polar (0.4-2.0) and ionic (2.0-above)

VSEPR

A = central atom, X = connected atoms, E = free electron pair. Linear, Bent, Trigonal planar, Trigonal Pyramidal, Square planar, Tetrahedral, Trigonal bipyramidal, Octahedral

Redox

Oxidator = acceptor of electrons, gets reduced. Reductor = donor of electrons, gets oxidised.

Oxidations number rules

O.N ion = charge, oxidation is increase in O.N, hydrogen -1 in compounds with metals and +1 in compounds with non-metals, oxygen -2 (except in O2-), halogens -1 (except when bound with oxygen)

Chemical names importance

carboxylic acid (-oic acid), aldehyde (-al, formyl-), ketone (-one, oxo-), alcohol (-ol, hydroxy-), amine (-amine, amino-), other

Zeroth Law of Thermodynamics

if two systems are in thermal equilibrium with a third system, then they are in thermal equilibrium with one another

First Law of Thermodynamics

Conservation of energy in a system

Second Law of Thermodynamics

entropy of an isolated system never decreases

Third Law of Thermodynamics

entropy of a closed system at thermodynamic equilibrium approaches a constant value when its temperature approaches absolute zero.

Charles’ Law

V/T=constant

Gay-Lussac’s Law

p/T=constant

Boyle’s Law

pV=constant

work

w is the work done on the system. when a gas expands by pushing against an external force the work is negative (-w=w’)

heat

+q: heat is absorbed by the system (an endothermic process), -q: heat is given out by the system (an exothermic process)

Enthalpy

a measure of the total heat energy absorbed or released in a thermodynamic system

Spontaneous, irreversible reaction

delta S > 0

reversible process

delta S = 0

delta H>0, delta S > 0

possible at high T

delta H>0, delta S < 0

not possible

delta H<0, delta S > 0

always possible

delta H<0, delta S < 0

possible at low T

Keq<1

reactants are favoured at equilibrium

Keq>1

products are favoured at equilibrium

Equilibrium: pressure increase

reaction producing the least amount of moles of gas is favoured

Equilibrium: temperature increase

endothermic reaction (delta H>0) is favoured

Equilibrium: temperature decrease

exothermic reaction (delta H<0) is favoured

Reaction rates

1 = concentration doubles → rate doubles (ln[R] to t → -k), 2 = concentration doubles → rate quadruples (1/[R] to t → k), 0=rate not dependant on concentration ([R] to t → -k)

Electrochemical cells

Galvanic = spontaneous reaction PORN, Electrolytic = non-spontaneous