El Camino College Chemistry 21A Dr. Dragan Marinkovic FORCES BETWEEN PARTICLES NOBLE GAS CONFIGURATIONS 1 2 He 2 10 Ne 3 18 Ar 4 36 Kr 5 54 Xe 6 86 Rn

El Camino College Chemistry 21A Dr. Dragan Marinkovic

FORCES BETWEEN PARTICLES

NOBLE GAS CONFIGURATIONS

1 2

He

2 10 Ne

3 18 Ar

4 36 Kr

5 54 Xe

6 86 Rn

PERIOD GROUP




1 2

He

2 10 Ne

3 18 Ar

4 36 Kr

5 54 Xe

6 86 Rn

PERIOD GROUP

Rn

1s2

2s2 2p6

3s2 3p6

4s2 3d10 4p6

5s2 4d10 5p6

6s2 4f14 5d10 6p6

1s2

2s2 2p6

3s2 3p6

4s2 3d10 4p6

5s2 4d10 5p6

1s2

2s2 2p6

3s2 3p6

4s2 3d10 4p6

1s2

2s2 2p6

3s2 3p6

1s2

2s2 2p61s2

VALENCE SHELL ELECTRONS

28

88

88

NOBLE GASES = INERT GASES




Lewis structures of the elements in the first two periods.

Ne=

1s2

2s2 2p61s2

2s2 2p5

1s2

2s2 2p4

1s2

2s2 2p3

1s2

2s2 2p2

1s2

2s2 2p1s2

2s2 1s2

2s 1s21s

OCTET RULE : atoms will gain or lose sufficient electrons to achieve

an outer electron arrangement identical to that of a noble gas.

By G. N. Lewis and Walter Kossel Predicts electron behavior in reacting atoms.

usually 8


FORCES BETWEEN PARTICLESIONIC BONDING, IONIC COMPOUNDS

During some chemical interactions the OCTET RULE is satisfied when electrons are transferred from one atom to another.

Na Na+ + e-

Cl + e- Cl-

Na + Cl Na+Cl-

Mg Mg2+ + 2e-

O + 2e- O2-

Mg + O Mg2+O2-

Ca Ca2+ + 2e-

2F + 2e- 2F-

Ca + 2F Ca2+F2-

SIMPLE ION : an atom that acquired a net positive or negative charge by losing or gaining electrons.

IONIC BOND : the attractive force that holds together ions of opposite charge.



IONIC BONDING; IONIC COMPOUNDS

metals lose electronsGENERAL RULE during bond formation

nonmetals gain electrons

ISOELECTRONIC = “same electronic” (configuration)

ISOELECTRONIC = same noble gas electronic configuration, but atoms DO NOT turn into the noble gases – they still have their unique number of protons and ONLY number of protons determines elements.

Mg Mg2+ + 2e-

O + 2e- O2-

Mg + O Mg2+O2-

Ca Ca2+ + 2e-

2F + 2e- 2F2-

Ca + 2F Ca2+F2-

IONIC COMPOUNDS

Formulas represent the combining ratio of positive and negative ions found in compounds. This ratio is determined by the charges on the ions, which are determined by the number of electrons

transferred.



IONIC BONDING; IONIC COMPOUNDS

BINARY COMPOUNDS = compounds made up of two different elements.

BINARY COMPOUND NAME = METAL + NONMETAL STEM + IDE.

nonmetal atom stem carbon carb- nitrogen nitr- phosphorus phosph- arsenic arsen- oxygen ox- sulfur sulf- selenium selen- fluorine fluor- chlorine chlor- bromine brom-

CuF CuF2

copper(I) fluoride copper(II) fluoride cuprous fluoride cupric fluoride

CoO Co2O3

cobalt(II) oxide cobalt(III) oxidecobaltous oxide cobaltic oxide

Co3O4 cobalt(II,III) oxide!!! (CoO·Co2O3) mixed valence compound

cobalt blue

FeCl2 FeCl3iron(II) chloride iron(III) chlorideferrous chloride ferric chloride



IONIC BONDING

MOLECULES are the smallest particle of pure substance that has properties of that substance and is capable of stable independent existence.



IONIC BONDING


Compound formula is a symbol for the molecule of a compound, consisting of the symbols of the atoms found in the molecule.

Some compound formulas are used to represent a single molecule.

Molecular formulas represent the precise number of atoms of each element found in a molecule.



IONIC BONDING


Compound formula is a symbol for the molecule of a compound, consisting of the symbols of the atoms found in the molecule.

Some compound formulas are used to represent a single molecule.

Molecular formulas represent the precise number of atoms of each element found in a molecule.

Formulas of ionic compounds represent only a simplest combining ratio of the ions in the compounds.

A stable form of an ionic compound is not a molecule, but a CRYSTAL in which many ions of opposite charge occupy LATTICE SITES in a rigid three dimensional arrangement called a CRYSTAL LATTICE.



IONIC BONDING

CuF2

NaClNa Na+ + e-

Cl + e- Cl-

Na + Cl Na+Cl-

Rigid three dimensional arrangement is called a CRYSTAL LATTICE.



IONIC BONDING

Na + Cl Na+Cl-

Formulas of ionic compounds represent only a simplest combining ratio of the ions in the compounds.

However, formulas are still used, especially in equations representing

chemical reactions, or when the MOLE concept is applied in

chemical formulas.

23.0 + 35.5 = 58.5

When the ATOMIC WEIGHTS making up a true molecular formula are added together, the result is the MOLECULAR WEIGHT of the compound.

For the ionic compounds we call it FORMULA WEIGHT.

The term FORMULA WEIGHT can be used for both ionic compounds and molecular compounds.


FORCES BETWEEN PARTICLESCOVALENT BONDING

A chemical bond is a strong attraction between two or more

atoms.

Bonds hold atoms in molecules and crystals together.

There are many types of chemical bonds, but all involve

electrons which are either shared or transferred between the

bonded atoms.



A chemical bond is a strong attraction between two or more

atoms.

Bonds hold atoms in molecules and crystals together.

There are many types of chemical bonds, but all involve

electrons which are either shared or transferred between the

bonded atoms.It is known that the stable form of gases, like oxygen, nitrogen and chlorine are diatomic molecules O2, N2 and Cl2. Obviously, such molecular bonds cannot be formed by electron transfer from one atom to another like in ionic molecules.

G. W. Lewis proposed that in these molecules VALENCE SHELL ELECTRONS ARE SHARED in order to satisfy the OCTET RULE for EACH of the ATOMS.

Such BONDS are called COVALENT BONDS.



Noble gas configuration (in this case, that of neon, s2p6) is achieved when two fluorine atoms (s2p5) are able to share an electron pair, which becomes the covalent bond. Notice that only the outer (valence shell) electrons are involved.

H· + H· H:H or H-H



In the Electron Dot Notation, the dots represent electrons that are involved (or have the potential to be involved) in forming covalent bonds between atoms. Alternatively, each covalent bond (electron pair) may be represented by a solid line.

DOUBLE and TRIPLE BONDS result from sharing two and three pairs of electrons, respectively.

Ammonia, NH3


FORCES BETWEEN PARTICLESPOLYATOMIC IONS

POLYATOMIC IONS are COVALENTLY BONDED GROUPS

of atoms that carry a NET ELECTRICAL CHARGE.With the exception of NH4

+, polyatomic ions are

NEGATIVELY CHARGED.


FORCES BETWEEN PARTICLESPOLYATOMIC IONS

phosphate


FORCES BETWEEN PARTICLESSHAPES OF MOLECULES AND POLYATOMIC IONS

Most molecules and polyatomic ions do NOT have flat (planar, two-dimensional) shapes, but three dimensional shapes.

The valence shell electron pair repulsion (VSEPR) model focuses on the bonding and nonbonding electron pairs present in the outermost (“valence”) shell of an atom that connects with two or more other atoms. The covalent model of chemical bonding assumes that the electron pairs responsible for bonding are concentrated into the region of apace between the bonded atoms.

If the central atom also contains one or more pairs of nonbonding electrons, these additional regions of negative charge will behave very much like those associated with the bonded atoms. The orbitals containing the various bonding and nonbonding pairs in the valence shell will extend out from the central atom in directions that minimize their mutual repulsions.



A simple triatomic molecule of the type AX2 has its two bonding orbitals 180° apart, producing a molecule that we describe as having linear geometry.

In an AX3 molecule such as BF3, there are three regions of electron density extending out from the central atom. The repulsion between these will be at a minimum when the angle between any two is (360° ÷ 3) = 120°. This requires that all four atoms be in the same plane; the

resulting shape is called trigonal planar, or simply trigonal.



Methane, CH4, contains a carbon atom bonded to four hydrogens. What bond angle would lead to the greatest possible separation between the electron clouds associated with these bonds? In analogy with the preceding two cases, where the bond angles were 360°/2=180° and 360°/3=120°, you might guess 360°/4=90°; if so, you would be wrong. The latter calculation would be correct if all the atoms were constrained to be in the same plane (we will see cases where this happens later), but here there is no such restriction. Consequently, the four equivalent bonds will

point in four geometrically equivalent directions in three dimensions corresponding to the

four corners of a tetrahedron centered on the carbon atom. The angle between any two

bonds will be 109.5°.This is called tetrahedral coordination.



SO42-

PO43-



The water molecule

ammonia


FORCES BETWEEN PARTICLESTHE POLARITY OF COVALENT MOLECULES

Cl2 (Cl-Cl)



Cl2 (Cl-Cl) Cl-Br δ-Cl-Brδ+

δ- δ+δ- and δ+




δ- δ+δ- and δ+

Linus Carl Pauling (1901–1994)

Nobel Prize in Chemistry (1954)Nobel Peace Prize (1962)

The electronegativity of an atom denotes its relative electron-attracting power in a chemical bond.

The 0-4 electronegativity scale of Pauling An atom that has a small electronegativity is said to be electropositive.

The metallic elements are generally electropositive.




δ- δ+δ- and δ+

nonpolarcovalent bond

polarcovalent bond

polarcovalent bond

bond polarization

partial ioniccharacter of

covalent bond

Using Electronegativity to Identify Ionic, Covalent, and Polar Covalent Compounds

NaCl SrBr2

Cl EN = 3.16 Br EN = 2.96Na EN = 0.93 Sr EN = 0.95 ∆EN = 2.23 ∆EN = 2.01

CH4 SO2

C EN = 2.55 O EN = 3.44H EN = 2.20 S EN = 2.58 ∆EN = 0.35 ∆EN = 0.86

H2OO EN = 3.44H EN = 2.20 ∆EN = 1.24

ionic compounds covalent compounds

polarmolecule

polarmolecule

nonpolarmolecule



ionic bond

non-polar covalent bond

polar covalent bond


FORCES BETWEEN PARTICLESOTHER INTERPARTICLE FORCES

Ionic and covalent bonding explains certain properties of substances. Some experimental observations can be explained only by proposing other types of forces between particles.

Ionic compounds in solid state form crystal lattice. Actually, most pure substances (molecules or atoms) form crystal lattices in solid state.

When heated, solids melt and forces holding particles in dense organized form weaken and particles move about more freely – in liquid state.

More heating overcomes attractive interparticle forces even more turningthe liquid into a gas or vapor (the liquid boils). Interparticle forces are minimal and particles move about freely – gas (vapor) state.



Melting and boiling points can give us indication of the strength of interparticle forces that are being overcome.



Melting and boilingpoints can give us indication of thestrength ofinterparticle forcesthat are being overcome.

Melting Points and Boiling Points of Substances with Similar Formula Weights

Substance FW (g/mol) mp (°C) bp (°C)

F2 38 -220 -188

NO 30 -164 -152

CH3OH 32 -94 65

Ca 40 893 1484

NaF SiO2

42 60

993 1610

16952230

NETWORK SOLID

- lattice sites areoccupied by atomscovalently bonded.

METALLIC BOND

Attraction betweenpositively chargedatomic kernels tahtoccupy lattice sites

and mobile electronsthat move freely

through the lattice.

DIPOLAR FORCE

the attractive forcebetween the positive

end of one polarmolecule and the negative end of

another.

HYDROGEN BONDING

attractive dipolar forcesbetween molecules in

which hydrogen atoms are covalently bonded to very electronegativeelements (F, O, or N).



DIPOLAR FORCE

the attractive forcebetween the positive

end of one polarmolecule and the negative end of

another.

HYDROGEN BONDING

attractive dipolar forcesbetween molecules in

which hydrogen atoms are covalently bonded to very electronegativeelements (F, O, or N).

MOLECULES WITHHYDROGEN BONDS.

water

hydrogen fluorideammonia

NO or CO



Temp( °C )n

Densitypure water

( g/cm3 )

0 (solid) 0.9150

0 (liquid) 0.9999

4 1.0000

20 0.9982

40 0.9922

60 0.9832

80 0.9718

100 (gas) 0.0006

Molecule b.p. (oC)

H2O 100H2S -60.3H2Se -41.3

‘UNIQUENESS OF WATER”

The strong hydrogen bonds orient H2O molecules into a very open 3-D crystal lattice when it freezes.The open lattice occupies more space than liquid.



e.g. H2, F2, O2, N2

Covalent bonds >

Metallic bonds >

Ionic bonds >>

Hydrogen bonding >

Dipole-dipole interactions >

Dispersion forces

400 kcal > > >> 12-16 kcal > 2-0.5 kcal > less than 1 kcal

Dispersion forces very weak attractive forces acting between particles of ALL matter. The result from momentary non-symmetric electron distributions in molecules or atoms.

Relative strength of interparticle forces


FORCES BETWEEN PARTICLESNAMING OF COMPOUNDS

Number Greek Latin½ hemi- semi-/demi- 1 mono- uni- 1¼ quasqui- 1½ sesqui- 2 di- duo-/bi- 3 tri- tre-/ter- 4 tetra-/tetr- quadri-/quadr- 5 penta-/pent- quinque-/quinqu- 6 hexa-/hex- sexa-/sex-7 hepta-/hept- septua- 8 octa-/octo-/oct- 9 ennea- nona-/non- 10 deka-/deca- deci- 11 hendeca- undec- 12 dodeca- duodec- 13 triskaideka- tridec- 14 tetradeca- quattuordec15 pentadeca- quindec- 16 hexadeca- sedec- 20 icosa- vigen- 100 hecto-/hect- centi- 1000 chilia-/kilo- milli- 10000 myria-


FORCES BETWEEN PARTICLESNAMING OF COMPOUNDS

Number Greek Latin½ hemi- semi-/demi- 1 mono- uni- 1¼ quasqui- 1½ sesqui- 2 di- duo-/bi- 3 tri- tre-/ter- 4 tetra-/tetr- quadri-/quadr- 5 penta-/pent- quinque-/quinqu- 6 hexa-/hex- sexa-/sex-7 hepta-/hept- septua- 8 octa-/octo-/oct- 9 ennea- nona-/non- 10 deka-/deca- deci- 11 hendeca- undec- 12 dodeca- duodec- 13 triskaideka- tridec- 14 tetradeca- quattuordec15 pentadeca- quindec- 16 hexadeca- sedec- 20 icosa- vigen- 100 hecto-/hect- centi- 1000 chilia-/kilo- milli- 10000 myria- +1 -1 -2 -3

NH4+ (ammonium) OH- (hydroxide) CO3

2- (carbonate) PO43- (phosphate)

NO3- (nitrate) SO4

2- (sulfate) ClO3

- (chlorate) CrO42- (chromate)

ClO4- (perchlorate) Cr2O7

2- (dichromate) MnO4

- permanganate) HCO3

- (hydrogen carbonate)

Examples:

CrO3 chromium trioxideNaOH sodium hydroxideKMnO4 potassium permanganateOsO4 osmium tetroxideSF6 sulfur hexafluoride(NH4)2CrO4 (di)ammonium chromateLi3PO4 trilithium phosphatePCl5 phosphorus pentachloride



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El Camino College Chemistry 21A Dr. Dragan Marinkovic FORCES BETWEEN PARTICLES NOBLE GAS CONFIGURATIONS 1 2 He 2 10 Ne 3 18 Ar 4 36 Kr 5 54 Xe 6 86 Rn