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General Chemistry CourseTitular: Lecturer Dr. Eneca Alexandru
Transilvania University of BraovChemistry Department
Is not allowed during the course:- to make tel. calls;- to make photos.
General chemistry2007-2008
First point
1. What its chemistry?2. Material and chemistry
Atoms and molecules
1. Electronic structure of the atom2. Chemistry bounds
Quantitative aspects (chemistry of the solution)
1. Chemistry reactions2. Reactions with protons transfer3. Reactions with electrons transfer4. Aqueous solutions5. Reactions with ligands fixation6. Chemistry kinetic7. Chemistry analytic
Sorcery
Alchemy
Important Figures in Chemistry (and not only)
Descartes
R. Boyle
A. Lavoisier
J. Dalton
D. Mendeleev
Just a short history
Just a short history
Natural science:
study of the natural phenomena; experiments; interdisciplines.
CHEMISTRY PHYSICS
BIOLOGY GEOLOGY
HYPOTESIS
EXPERIMENT
THEORY, LAWMODELS
UP-GRADE
How the (natural) science work?
We are focused on:- atoms and molecules;- quantitative aspect of the chemical reactions;
- three type of chemical reactions: proton, electrons andsubstrate transfer;- analytical chemistry.
thermodynamic
kinetic
mas
s bala
nce
Course 1
Matter and chemistry
1.1 Matter states
1.2 Atoms, molecules and ions
1.3 Moles and concentration
1.4 Chemical bounds and the nature of the chemicalcompound
Matter states:
Gas free particles in low motion (specific mass env. 10-3gcm-3)
Liquid mobile particles yielding intermolecular forces(specific mass env. 1 gcm-3)
Solid motionless particles (specific mass 1-20 gcm-3)
Other matter states
Liquid crystal intermediary state with a medium order of the particles
Other matter states
Plasma an ionized gas where the electrons in the atomare separate from the nucleus, usually considered to bethe fourth distinct state of matter.
E.g. stars (sun), ionosphere
Application:LampsTV screenNuclear fusion
Phase transformation: physics or chemistry?E.g.: water, universal solvent
Water molecules are formed from two hydrogen atoms boundedwith an oxygen atom by covalent bounds. The water molecules arepartially charged, inducing a dipol moment.
Covalent bonds
Water molecules ingaseous phase
Partial charged atoms form the molecule interacts with the neighbormolecules, forming slim (low energy) bounds called hydrogen bounds.
Hydrogen bound
Energy:
So, isolated water molecules in gas phases have different propertiescomparing with the liquid phase.
Water inliquid phase
Hydrogenbounds: 80%
Ice (water in solid phase)Hydrogen bounds: 100%
Mixture
Heterogen Homogen
CompoundsElements
MoleculesAtoms
Nucleus Electrons
Macroscopicscale
Microscopicscale
Physical process
Physical process
Chemical process
Chemical process
Back to atomsback to the origin
How theatomswere
born???BIG BANG Theory
15 billions years ago
Nuclear fusion
Quarks formation
The structure of the atom (Atomic structure)
W. Thomson develops the plum pudding model: a cloud of positive charges; randomly distributed electrons.
E. Rutherford develops an experimental model where the particle (the charge is +2and the relative atomic weight is 4) depart from the source and pass through a thin goldfoil.He registers the deviation of the particles:
most of the particles are not deviated (there is plenty of empty space in theatom); some of the particles are slightly deviated (there are negatively chargedparticles, with much lower mass then the particles, in the atom theelectrons); few particles are turned (there is a concentrated, positive atomic charge withthe mass comparable to the particles).
Conclusion: Nuclear model
all the positive charge and quite the entire mass of atom is concentrated in a nucleus; the electrons are surrounding the nucleus.
The chemical reactions do not affect the nucleus. Thesum of the protons in the nucleus is called atomic number (Z).
+11p proton 01n neutron
The sum of the proton and neutron is called massnumber (A). Two species having the same Z and different A are isotopes.
E.g. 11H (proton); 21D (deuterium); 31T (tritium)
Some rules for filling the orbital up
There are not two species with all the quantum numbers equal (Paulis ExclusionPrinciple).
n = principal quantum number describes the energetic level of orbital (how far is theorbital from the nucleus); n = 1, 2,3 .
l = azimuth quantum number describes the shape of the orbital; for n fixed,l = 1, 2,3, (n-1)
m = magnetic quantum number describe the orientation of the orbital; for n,l fixed,m = -l, -(l-1), -(l-2), , 0, , (l-2), (l-1), l
s = spin number describe the electron movement around its own axis,s= +1/2 and 1/2
Consequence
In one orbital there are maximum two electrons.
8s7p6d5f
7s6p5d4f
6s5p4d
5s4p3d
4s3p
3s2p
2s
1s
E.g.
11Na31Ga
Chemical elements
Every elements is charactrised by:- name;- chemical symbol.
Atomic number = proton numberfrom the nucleus (its also theelectron numbers)
Chemical symbol
Atomic mass
Information from the periodictables of the elements
Atomic mass
MA = pi mi pi = isotopic abundancemi = isotopic mass
Units: 12 daltons = atomic mass of 12C1 daltons (Da) = 1.660510-24 g
E.g. Chlorine35Cl: 75,5% 37Cl: 24,5%MA = 350,755 + 370,245 = 35,5 DaMA exacte = 35,453 Da
Atomic massAtomic mass
The mass numbermass number of an element, A, is the number of nucleons (protonsand neutrons) in the atomic nucleus.Different isotopes of a given element are distinguished by their massnumbers, which are conventionally written as a super-index on the lefthand side of the atomic symbol (e.g., 238U).The relative atomic massrelative atomic mass of an element is the average of the atomicmasses of all the chemical element's isotopes as found in a particularenvironment, weighted by isotopic abundance, relative to the atomic massunit (u). This number may be a fraction which is not close to a wholenumber, due to the averaging process.On the other hand, the atomic mass of a pure isotope is quite close to itsmass number.
Naturally occurring carbon consists of three isotopes, 12C, 13C, and14C. State the number of protons, neutrons, and electrons in each ofthese carbon atoms.
12C 13C 14C6 6 6
#p+ _______ _______ _______
#no _______ _______ _______
#e- _______ _______ _______
ExerciseExercise
12C 13C 14C6 6 6
#p+ 6 6 6
#no 6 7 8
#e- 6 6 6
AnswersAnswers
An atom has 14 protons and 20 neutrons.A. Its atomic number is
1) 14 2) 16 3) 34B. Its mass number is
1) 14 2) 16 3) 34
C. The element is1) Si 2) Ca 3) Se
D. Another isotope of this element is1) 34X 2) 34X 3) 36X
16 14 14
Learning CheckLearning Check
Allotropy
Allotropy is a behavior exhibited by certain chemical elements: theseelements can exist in two or more different forms, known as allotropes ofthat element. In each different allotrope, the elements atoms are bondedtogether in a different manner.
Allotropic forms of the carbon
GraphiteDiamond
Molecular Mass (MM)
MM = niMAini = nb of atoms iMAi = atomic mass of atoms i
E.g.
Water H2OMM = 21,008 + 115,999 = 18,015 daltons
Glucose C6H12O6
MM = 612,011 + 121,008 + 615,999 = 180,156 daltons
IonsAn ion is as atom or molecule which has lost or gained one or moreelectrons, making it negatively or positively charged.
Formation of positive charged ions (cation)
Atome Cations + Electrons
Cu Cu+1 + 1e-Cu Cu+2 + 2e-
Formation of negative charged ions (anions)
Atoms + Electrons Anions
Cl + 1e- Cl-1S + 2e- S-2
Charges on Common IonsCharges on Common Ions
-1-2-3+1+2
By losing or gaining eBy losing or gaining e--, atom has same number, atom has same numberof eof e--s as nearest Group 8A atom.s as nearest Group 8A atom.
Remember from the first chemistry course
Mole is a quantity of substance containing NA particlesParticles = atoms, molecules or ions
NA = 6.0221023 atoms/mol
Molar Mass (MM)Mass of one mol from a substance, expressed in grams
The molar mass is equal with the molecular mass (or atomic), expressedin grams.
E.g. water H2O
Molecular mass = 18.015 Da ; Molar mass = 18.015 mol/g
Exercise
WaterHow many moles are in 1kg of water?
1000 g / 18.015 g/mol = 55,5 mol
How many molecules are in 1kg of water?
55,5(6,0221023) = 3,341025 molecules
Iron MA = 55,847 daltons1mole = 55,847g, contain 6,0221023 atomes
How many atoms are in 1g?
1g / 55,847 g/mol = 0.0179 mol0,0179(6,0221023) = 1,0781022 atoms
?
The Chemistry Laws
Ca(OH)2 + 2HNO3 Ca(NO3)2 + 2H2OCalcium hydroxide + Nitric acid Calcium nitrate + Water
Consequence: the coefficients
The low of perfect gas
An perfect gas is a gas where the molecules dont suffer anyinteractions.
PV = nRT
P pressure (Pascal Pa, 1 Pa = 1Nm-2 = 1kgm-1s-2;1 atm = 1,014105 Pa
V volume (m3)
n moles number
T temperature (K)
R perfect gas constant (8,31 Jmol-1K-1 = 8,31 kgm2s-2mol-1K-1
Exercise ?1) What is the volume occupied by 1 mol of perfect gas at 0C and 1 atm?
n = 1T = 273,15 KP = 1 atm = 1,014105 Pa
V = nRT / P = (18,31273,15) / 1,014105 = 2,270103 / 1,014105 = 2,2410-2 m3
1m3 = 1000litres, V = 22,4 liters1 mol occupied 22,4 liters at 0C and 1 atm
2) What is the volume occupied by 1 mol of perfect gas at 25C and 1 atm?n = 1T = 298,15 KP = 1 atm = 1,014105 Pa
V = nRT / P = (18,31298,15) / 1,014105 = 2,478103 / 1,014105 = 2,4410-2 m3
1m3 = 1000litres, V = 24,4 liters1 mol occupied 24,4 liters at 25C and 1 atm
Einorganic acid = Macid / number of hydrogen atomse.g.EH2SO4/SO42- = M/2 = 98/2
Eorganic acid = Macid / number oh carboxyl groups
Ebases = Mbases / number of hydroxide groupse.g.ENaOH = M/1 = 40/1
Esalt and metallic oxide = M / number of metal atoms xvalencee.g.ECaO = M/2*1 = 56/2
Eelectrochemical reaction = A element / number of exchangedelectronse.g. 2Al + 3 Cl2 = 2AlCl3EAl = AAl/3 = 27/3
Calculation of chemical Equivalents
The Law of chemical equivalents the ratio between the mass and the chemicalequivalent is a constant for each participant in a chemical reaction.
The Quantum model
1. The duality particle wave.2. The Principle of uncertainty (Heisenberg) for a dual particle we cant explicit the
position and the moment when that place is likely to be occupied.
Definition: The region of space where the electrons can be found with the mostlikelihood is called orbital.
The Chemical Bonds
The chemical bonds are formed by the valence electrons (the electrons from theexterior shell) due to the electronic interactions.
Its characterized by the distance, called bonds length (O-H : 96 pm) and by theenergy (O-H : 437 kJ/mol)
There are several type of chemical bond that allow to classified differentcompounds
Chemicalbond
The Chemical Bonds
1.The Ionization Energy represents the energy necessary for one electron to leave the last shell.I in group
< I > = Joule, eVI in period
2. Affinity is the energy necessary necessary for accepting one electron on the last shell of one atom.
A in group< A > = J, eV
A in period
3. XR = Relative Electronegativity< X > = J, eV
A BXR, A XR, B
XR, AB = XR, A XR, B
We can have:
A A, covalent non polar bonda) C H, covalent non - polar bond XR, AB = 0
M M, metallic bond
b) A+ B-, ionic bond XR, AB > 2.3
c) A B, covalent polar bond 0< XR, AB < 2.3
The Ionic Bond
If the relative electronegativty of an atom is low, there is a tendencyof releasing electrons. The atom is converted in a positive ion ancation - via oxidation. Metal atoms are usually easily oxidized.
If an atom has a high relative electronegativity, it has the possibilityto accept electrons via the reduction process and the atom turnsinto a negatively charged ion - a anion.
Between the anions and cations the ionic bond is formed.
e.g.: NaF
2311Na0 2311Na+
1s2 2s2 2p6 3s1 [ 1s2 2s2 2p6 ]+ oxidation
179F0 179F-
1s2 2s2 2p5 [ 1s2 2s2 2p6 ]- reduction
e1
e1
+ e1
+ e1
Properties of the ionic substances
The driving force in an ionic substance is the electrostatic force (attractive amongdifferently charged ions, repulsive among ions of same sign).
Felectrostatic strong forces in solids, orientating ions of alternative charges
solid crystalline state: breakable, with medium mechanicalproperties
optical properties: transparent, colored or colorless: used asoptical prisms (KCl, KF)
conduction properties: the conduction is possible in the presenceof free charges: - solid state (charges in fixed positions):
insulators- liquid state (melts and solutions) the charges
are free to move: ionic conductors
Solubility ionic substances are soluble in polar substances
Haber Born cycle a very good example for energy calculation:
in this case we need to know the energy lattice that can be calculate by measuring thesublimation energy of the ionic substances.
Overall reaction: Na (s) + Cl2(g) Na+Cl-(s)
Metallic bonds
Three-dimensional packingof metallic ions
Iron: central cubic crystallinestructure
Copper: central cubic with centralfaces crystalline structure
The covalent bondNon polar covalent bonds
Between two identical atoms.
Simple covalent molecules example:
Hydrogen: simple bondOxygen: double bondNitrogen: triple bond
Represent one free electron pair which imposesome special properties:- Lewis acidity;- possible intermolecular interactions (non-covalent bonds)
Polar covalent bonds
Between two different atomsa) Molecular compoundsFinite structure
Polar bondsPolar molecule
Polar bondsNon-Polarmolecule
carbon dioxide CO2(responsible for thegreenhouse effect)
C = O, carbon monoxide polar substance (easilyabsorbed by blood lethalintoxication)
CCl4 - try to see the symmetry in this substance:(Carbon tetrachloride ) because this propertiesinduces the non polarity
Non polar substances: CH4 (methane), HC CH (acetylene), C6H6 (benzene)Polar substances: H2O, NH3, HX, SO2, SO3, NxOy.
The multiplicity:
H . .Simple covalent bond: H H, H C H , H O , H N H
H H
H
Double covalent bond: O = O, O = C = O
H O O\
S sulfuric acid \\
H O O
H3C\C = O acetone
H3C
Triple covalent bonds: N N, H C N, H C C R
Do you know what represent the hybridization?
It is a process due to each electrons from the last shell (inthe carbon atom) on the s and p orbitals get the sameenergy and become equivalent.
For example in the acetylene molecule the carbon atomsare hybridized sp and there are two bond types: one typeis the bond for C H bond and C C bond and theother is the bond (the other two bonds in C = C).
So, the covalent bond is formed with minimum twoelectrons (one for each atom) and maximum 6 electrons(three for each atom).
b) Macromolecular compounds and polymers
Infinite structureIts formed by the condensation of small molecules
Poly(ethylene)terephtalate (PET)
c) Crystalline covalent solids
Three-dimensional packing of infinite number of atoms bonded in acovalent manner.
Other examples: diamond, graphite
d) Amorphous covalent solids
E.g. Glass, plastics
Ion dipole bonds and the metal complex(coordination bonds)
Between an metal ion (usually a cation) and a polar molecule
Notes:1) This bond its usually considered as a non-covalent bond;2) One molecule can contain different type of chemical bond.
(in this case we have coordination bond and covalent bond)
Intermolecular bonds
1. The van der Waals bond: between non polar moleculesCharacteristic: very weak but additive
E.g.:Small molecule: H2, O2, N2, CO2. gasesLarge molecule: -(- CH2 CH2 -)n- polymer (solid)Solubility YES in non polar solvents (C6H6, CCl4)
NO: in polar solvents (H2O)Conductivity: insulators
2. the Keessom bond: polar molecule polar molecule< 1
+ - + -dipol - dipol bond (weak force)
3. Hydrogen bonds (dipole dipole)
Length OH 180 200 pmDegree HOH 120-180