Units

• The system of units in chemistry is the SI system(Systemic International)

• conversions

• mass: 1pound= 0.4356kg(453.6g)

• -volume: 1 quart = 0.9464 dm3(0.9464 L)

• length: 1 inch = 2.54 cm

• The SI unit for volume is the cubic meter (m3),

• On the Celsius scale, water freezes at 0°C and boils at 100°C.

• C= 5/9[F-32]

• F=5/9(C)+32

• the Kelvin scale. Water freezes at 273.15 K and boils at 373.15 K. To convert from Celsius to Kelvin: K = °C + 273.15

• Absolute zero is 0 K and is the point at which all molecular motion ceases.

• The density (D) of an object is calculated by dividing the mass of the object by its volume.

• The most common units for density in chemistry are g/cm3 or g/mL.

MEASUREMENTS

Two types of numbers in chemistry—exact and measured.

• Exact values are just that—exact, no uncertainty associated

• Measured value shave uncertainty associated with them because of the limitations of our measuring instruments

• Measured values answers must reflect the combined uncertainty by the number of significant figures that are reported in the final answer

• Rules for determining the number of significant figures in a measured value:

1. All non-zero digits (1, 2, 3, 4, etc.) are significant.

2. Zeros between non-zero digits are significant.

3. Zeroes to the left of the first non-zero digit are not significant.

4. Zeroes to the right of the last non-zero digit are significant if there is a decimal point present, but not significant if there is no decimal point.

• Another way to determine the number of significant figures in a number is to express it in scientific (exponential) notation. The number of digits shown is the number of significant figures. For example, 2.305 × 10-5 would contain 4 significant figures.

DIMENSIONAL ANALYSIS-FACTOR LABEL METHOD

• Mathematical operations are conducted with the units associated with the numbers, and these units are canceled until only the unit of the desired answer is left. This results in a setup for the problem

THE STATES OF MATTER

• Matter can exhaust in threes test: solid, liquid, gas

• Solid has definite shop and volume. The particles that make up a solid are close together and many times are locked into a very regular framework called a crystal lattice. Molecular motion exists slightly

• A liquid has a definite volume and no definite shape. It conforms to the container in which it is placed. The particles are moving much more than in the solid.

• A gas has neither definite shape nor volume. volume. It expands to fill the container in which it is placed. The particles move rapidly with respect to each other.

• indicate the state of matter that a particular substance is in by a parenthetical,l, or g.

THE STRUCTURE OF THE ATOM

• The first modern atomic theory was developed by John Dalton, presented in1808

• Dalton thought that atoms of an element are the same and atoms of different elements are different.

• 1897 J.J Thompson discovered the existence of the first subatomic particle electron. Using magnetic and electric fields

• 1909, Robert Millikan measured the charge on the electron in his oil-drop experiment (electron charge = -1.6022 × 10-19 coulombs), and from that, he calculated the mass of the electron.

• Thompson also developed an atomic model, the raisin pudding model which describes the atoms as being diffuse positively charged spheres with electrons scattered

• Ernest Rutherford, 1910, was investigating atomic structure by shooting positively charged alpha particles at a thin gold foil. Rutherford concluded from this scattering experiment that the atom was mostly empty space where the electrons were and that there was a dense core of positive charge at the center of the atom that contained most of the atom’s mass. He called that dense core the nucleus.

SUBATOMIC PARTICLES

• modern theory of the atom describes it as an electrically neutral sphere with a tiny nucleus at the center, which holds the positively charged protons and the neutral neutrons.

• The negatively charged electrons move around the nucleus in complex paths, all of which compose the electron cloud.

• Three fundamental subatomic particles

• Atoms of the same element (same number of protons) that have differing numbers of neutrons are called isotopes.

• Isotope symbol-- AXZ

• X represents the element symbol taken from the periodic table. Z is the atomic number of the element, the number of protons in the nucleus. A is the mass number, the sum of the protons and neutrons.

ELECTRON SHELLS, SUBSHELLS, ORBITALS

• the electrons in an atom are located in various energy levels or shells that are located at different distances from the nucleus.

• Within the shells, the electrons are grouped in subshells of slightly different energies.

• The number associated with the shell is equal to the number of subshells found at that energy level.

• The subshells are denoted by the symbols s, p, d, f, etc., and correspond to differently shaped volumes of space in which the probability of finding the electrons is high.

• The subshells are denoted by the symbols s, p, d, f, etc., and correspond to differently shaped volumes of space in which the probability of finding the electrons is high.

• The electrons in a particular subshell may be distributed among volumes of space of equal energies called orbitals.

• Be sure to fill the lowest energy levels first (Aufbau principle)

ELECTRONIC CONFIGURATIONS

• The electronic configuration is a condensed way of representing the pattern of electrons in an atom.

• Using the Aufbau build-up pattern consecutively write the number of the shell (energy level), the type of orbital (s, p, d, etc.), and then the number of electrons in that orbital shown as a superscript

PERIODIC TABLE

• In 1871, a Russian chemist, Dmitri Mendeleev, introduced the first modern periodic table.

ARRANGEMENTS OF ELEMENT

• One of the systems involves putting the elements in three main groups- metals. Nonmetals, metalloids

• Metals- are solid (mercury being an exception) shiny, and good conductors of heat and electricity, they are malleable and ductile

• Metalloids- have properties of both metals and nonmetals

• Nonmetals- poor conductors of heat and electricity, are not malleable or ductile. Gain electrons in their chemical reactions to form ions

• Another way to group elements is in terms of periods and groups

• Periods are horizontal rows that have consecutive atomic numbers. The periods are numbered from 1 to 7. Elements in the same period do not have similar properties in terms of reactions.

• The vertical rows are called groups or families.

• The groups that are labeled with an A are called the main-group elements, while the B groups are called the transition elements.

• Two other horizontal groups, the inner transition elements, have been pulled out of the main body of the periodic table.

• The Roman numeral at the top of the main-group families indicates the number of valence (outermost shell) electrons in that element.

• Valence electrons are normally considered to be only the s and p electrons in the outermost energy level.

• Four main group of families

  • IA group (Group 1)  -alkali metals

  • IIA group (Group 2) - alkaline earth metals

  • VIIA group (Group 17) - halogens

  • VIIIA group (Group 18) - noble gases

TRENDS IN PERIODIC TABLES

• The overall attraction on an electron experiences id due to the effective nuclear changes. This attraction is related to the positive nuclear charge interacting with negative electrons

• The size of an atom is generally determined by the number of energy levels occupied by electrons. This means that as we move from top to bottom within a group, the size of the atom increases due to the increased number of shells containing electrons.

• The greater the electron-electron repulsion, the larger the species becomes, and vice versa.

• The ionization energy (IE) is the energy needed to completely remove an electron from an atom.

• There are two factors affecting the magnitude of ionization energy. One is the size of the atom. The other factor is the magnitude of the effective nuclear charge.

• The electron affinity (EA) is the energy change that results from adding an electron to an atom or ion.

OXIDATION NUMBERS

• Oxidation numbers are numbers that help to balance redox

• Oxidation numbers are assigned to elements in their natural state or in compounds using the following rules:

  • The oxidation number of an element in its elemental form (i.e., H2, Au, Ag, N2) is zero.

  • The oxidation number of a monatomic ion is equal to the charge on the ion. The oxidation number of Mg2+ is +2. Note that the charge is written with a number first, then a sign; for oxidation numbers, it is a sign, then the number.

  • The sum of all the oxidation numbers of all the elements in a neutral molecule is zero. The sum of all the oxidation numbers in a polyatomic ion is equal to the charge on the ion.

  • The alkali metal ions have an oxidation number of +1 in all their compounds.

  • The alkaline earth metals have an oxidation number of +2 in all their compounds.

  • The oxidation number of hydrogen in compounds is +1, except it is -1 when combined with metals or boron in binary compounds.

  • The oxidation number of halogens in their compounds is -1 except when combined with another halogen above them on the periodic table, or with oxygen.

  • The oxidation number of oxygen is -2 in compounds, except for peroxides, in which it is -1.

NOMENCLATURE OVERVIEW

BINARY COMPOUNDS

Binary compounds are compounds that consist of only two elements.

• Binary compounds may be subdivided into metal type, nonmetal type, and acid type.

(a)Metal type These binary compounds begin with metals. The metal is given first in the formula.First name the metal, then name the nonmetal with the suffix ide.

ex:

Formula     Name

Na2O            sodium oxide

(b) Nonmetal type These binary compounds have formulas that begin with a nonmetal. Prefixes are used to indicate the number of each atom present.

Ex:

Formula  Name

CO          carbon monoxide

Carbon monoxide is one of the very few cases where the prefix mono is used. In general, you should not use mono in any other compound.

(c) Acid type These binary compounds have formulas that begin with hydrogen. If the compound is not in solution, the naming is similar to that of the metal type.

Ex: HCl(g), HF(l)

TERNARY  COMPOUNDS

• Ternary compounds are those containing three or more elements.

• If the first element in the formula is hydrogen, it is usually classified as an acid.

• If the formula contains oxygen in addition to the hydrogen, the compound is usually classified as an oxyacid. In general, if the first element in the formula is not hydrogen, the compound is classified as a salt.

• Ternary acids are usually named with the suffixes ic or ous. The exceptions are the

acids derived from ions with an ide suffix

• If an acid name has the suffix ic, the ion of this acid has a name with the suffix ate. If an acid name has the suffix ous, the ion has a name with the suffix ite.

WRITING FORMULAS

• To write the formula from the name of a binary compound containing only nonmetals, write the symbols for the separate atoms with the prefixes converted to subscripts.

• In all compounds the to total charge must be zero

• Ex: 1. Magnesium oxide

Mg^2+O^2- = +2-2 =0

This gives MgO

• If a polyatomic ion must be increased to achieve zero charge, parentheses should be used.

• One way of predicting the values of the subscripts is to crisscross the valences.

TRANSITION METALS

• Many transition metals and the group of six elements centered around lead on the periodic table commonly have more than one valence.

• Modern nomenclature rules indicate the valence of one of these metals with a Roman numeral suffix (Stock notation). Older nomenclature rules used different suffixes to indicate the charge.

COORDINATION COMPOUNDS

• Coordination compounds contain a complex.

• a complex may be recognized because it is enclosed in square brackets [ ]. The square brackets are omitted when the actual structure of the complex is uncertain.

• A complex is composed of a central atom, normally a metal, surrounded by atoms or groups of atoms called ligands.

• A complex may be ionic or neutral. An ionic complex is called a complex ion.

• A neutral complex is a type of coordination compound.

• When writing the formula for a complex, the ligands are listed alphabetically.

• Anionic complexes always have names ending in ate.

• If the metal ion may exist in more than one oxidation state, this oxidation state should be listed, in Roman numerals, immediately after the name of the metal ion.

COMMON MISTAKES TO AVOID

1. Always show your units in mathematical problems.

2. In the conversion from °F to °C, be sure to subtract 32 from the Fahrenheit temperature

first, then multiply by 5/9.

3. In the conversion from °C to °F, be sure to multiply the Celsius temperature by 9/5,

then add 32.

4. Don’t put more than 2 electrons in any individual orbital.

5. Always fill the lowest energy levels first.

6. Half fill orbitals of equal energy before pairing up the electrons.