ChemistryUnit 11: Modern Atomic Theory This concept of a nuclear atom resulted from Ernest

Rutherford’s experiments in which he bombarded metal foil with particles (see Section 4.5). Rutherford and his coworkers were able to show that the nucleus of the atom is composed of positively charged particles called protons and neutral particles called neutrons. Rutherford also found that the nucleus is apparently very small compared to the size of the entire atom. The electrons account for the rest of the atom.

Electromagnetic Radiation: Light Wavelength: (symbolized by the Greek letter lambda) is the

distance between two consecutive wave peaks Frequency: (symbolized by the Greek letter nu) indicates how

many wave peaks pass a certain point per given time period Speed: how fast a given peak travels through the water

Photons: tiny packets of energy An atom with excess energy is said to be in an excited state Quantized: having the same set of discrete energy levels The current theory of atomic structure is not the same as the

Bohr model. Electrons do not move around the nucleus in circular orbits

Wave Mechanical Model: new model for the hydrogen atom that seemed to apply equally well to other atoms

A probability map is called an orbital The hydrogen atom has discrete energy levels. We call these

levels principal energy levels and label them with integers The levels are subdivided into sublevels, represented by a

letter. Pauli exclusion principle: an atomic orbital can hold a

maximum of two electrons, and those two electrons must have opposite spins

Orbital diagram, also called a box diagram, in which orbitals are represented by boxes grouped by sublevel with small arrows indicating the electrons

valence electrons—that is, the electrons in the outermost (highest) principal energy level of an atom

inner electrons, which are known as core electrons, are not involved in bonding atoms to each other

Unit 12: Chemical Bonding Bond: force that holds groups of two or more atoms together

and makes them function as a unit Bond Energy: energy required to break the bond Ionic Bonding: an atom that loses electrons relatively easily

reacts with an atom that has a high affinity for electrons Ionic Compound: results when a metal reacts with a nonmetal Covalent Bonding: type of bonding we encounter in the hydrogen

molecule and in many other molecules where electrons are shared by nuclei

Polar Covalent Bond: the atoms are not so different that electrons are completely transferred but are different enough so that unequal sharing of electrons results

Bond Polarity: the electrons in the bonds are not shared equally

Electronegativity: the relative ability of an atom in a molecule to attract shared electrons to itself

o 0-0.4: nonpolar o 0.4-1.7: polaro 1.7-4: ionic

Dipole Moment: molecule such as HF that has a center of positive charge and a center of negative charge

A cation is always smaller than the parent atom, and an anion is always larger than the parent atom

Bonding involves just the valence electrons of atoms Lewis structure: representation of a molecule that shows how

the valence electrons are arranged among the atoms in the molecule

The most important requirement for the formation of a stable compound is that the atoms achieve noble gas electron configurations

Duet Rule: Hydrogen forms stable molecules where it shares two electrons. That is, it follows this

Octet Rule: Eight electrons are required to fill these orbitals, so the second-row nonmetals carbon through fluorine typically obey this

Bonding Pair: surrounded by eight valence electrons, two of which are shared with the other atom

Lone/Unshared Pairs: pairs of electrons that are not involved in bonding

Single Bond: two atoms sharing one electron pair Double Bond: two atoms sharing two pairs of electrons Triple Bond: three electron pairs are shared Resonance: more than one Lewis structure can be drawn for the

molecule Boron atom has only six electrons around it Beryllium takes up four electrons around it Any molecule that contains an odd number of electrons does not

conform to our rules for Lewis structures We use the word structure in another way when we talk about

the molecular structure or geometric structure of a molecule

Unit 13: Gases A device that measures atmospheric pressure, the barometer,

was invented in 1643 by an Italian scientist named Evangelista Torricelli

The unit mm Hg (millimeters of mercury) is often called the torr in honor of Torricelli. The terms torr and mm Hg are used interchangeably by chemists

1 standard atmosphere 1.000 atm 760.0 mm Hg 760.0 torr The SI unit for pressure is the pascal (abbreviated Pa). 1

standard atmosphere 101,325 Pa

pounds per square inch, abbreviated psi ( 1.000 atm = 14.69 psi)

Unit 14: Liquids and Solids The energy required to melt 1 mol of a substance is called the

molar heat of fusion. For ice, the molar heat of fusion is 6.02 kJ/mol

The energy required to change 1 mol of liquid to its vapor is called the molar heat of vaporization. For water, the molar heat of vaporization is 40.6 kJ/mol

Molecules with dipole moments can attract each other by lining up so that the positive and negative ends are close to each other, as shown in Figure 14.5a. This is called a dipole–dipole attraction

Particularly strong dipole–dipole forces occur between molecules in which hydrogen is bound to a highly electronegative atom, such as nitrogen, oxygen, or fluorine

That is, water molecules tend to remain together in the liquid state even at relatively high temperatures

The forces that exist among noble gas atoms and nonpolar molecules are called London dispersion forces

Atoms can develop a temporary dipolar arrangement of charge as the electrons move around the nucleus. This instantaneous dipole can then induce a similar dipole in a neighboring atom. The interatomic attraction thus formed is both weak and short-lived, but it can be very significant for large atoms and large molecules

Nonpolar molecules such as H2, N2, and I2, none of which has a permanent dipole moment, also attract each other by London dispersion forces. London forces become more significant as the sizes of atoms or molecules increase. Larger size means there are more electrons available to form the dipoles.

Liquids with high vapor pressures are said to be volatile—they evaporate rapidly

Unit 15: Solutions

Unit 16: Acids and Bases

Arrhenius concept of acids and bases was a major step forward in understanding acid–base chemistry, this concept is limited because it allows for only one kind of base—the hydroxide ion.

In the Brønsted–Lowry model, an acid is a proton (H) donor, and a base is a proton acceptor.

conjugate acid–base pair consists of two substances related to each other by the donating and accepting of a single proton.

The common strong acids are sulfuric acid, H2SO4(aq); hydrochloric acid, HCl(aq); nitric acid, HNO3(aq); and perchloric acid, HClO4(aq)

The HSO4ion is also an acid but it is a weak acid: Organic acids, those with a carbon-atom backbone, commonly

contain the carboxyl group; Acids of this type are usually weak. An example is acetic acid, CH3COOH, which is often written as HC2H3O2.

pH= -log[H+]

pOH= -log[OH-] To represent pH to the appropriate number of significant

figures, you need to know the following rule for logarithms: the number of decimal places for a log must be equal to the number of significant figures in the original number. Thus 2 significant figures [H] 1.0105 M and pH 5.00 2 decimal places

pH+pOH=14 solution is buffered by the presence of a weak acid and its

conjugate base

Unit 17: Equilibrium

Ignore liquids and solids Include gases and aqueous solutions Le Chatlier’s Principle

o when a reactant or product is added to a system at equilibrium, the system shifts away from the added component. On the other hand, if a reactant or product is removed, the system shifts toward the removed component

o Therefore, when the volume of a gaseous reaction system at equilibrium is decreased (thus increasing the pressure), the system shifts in the direction that gives the smaller number of gas molecules

o simply treat energy as a reactant (in an endothermic process) or as a product (in an exothermic process), and predict the direction of the shift in the same way you would if an actual reactant or product were being added or removed.

Ksp= [A+][B-] o And Solubility (in molar) = xA = xB, that is, the

molarity of the compound will be the same as its ions if their coefficients are the same.

Unit 18: Oxidation–Reduction Reactions and Electrochemistry