CHEM 111 Fall 2012: OWLBook Chapter 2

OWL Assignments Coming Due this Weekend!! Be sure to review units and pre-fixes on your own. This should

be material you covered in high school science.

Accuracy and Precision• Accuracy = how close you are to the known value• Precision = how reproducible (similar to each other)

your results are

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Chapter 2: Elements and Compounds

• Atomic Structure• Elements and Isotopes• The Periodic Table

• Covalent Compounds– Naming

• Ions and Ionic Compounds– Naming

Atomic Structure• Protons:

– Determine the identity of the element

• Neutrons– With protons in the nucleus– Stabilize the nucleus (or make it

unstable-radioactive)– Result in different isotopes

• Electrons– Exist outside of the nucleus– Alter the overall charge on an atom

• Adding or subtracting them makes ions

Alpha Particle Scattering-helped determine the structure of the atom

Subatomic Particles (for CHEM 111)

Cathode Ray (electron beam) Tube

Mass Spectrometer

Atomic Symbols

How many protons, neutrons, electrons are in:

Isotopes & Atomic Weight• Every form of a unique element

is one of its isotopes– Some elements only have one

isotope.• Remember-protons are what

make an element• Isotopes are forms of an

element with different masses• Adding or subtracting neutrons

from the nucleus makes isotopes

• Some isotopes are stable– Some are unstable

• Radioactive

Let’s look at some isotopes…Isotope Symbol # of Neutrons Fractional

(isotopic) Abundance

Property/Use

Hydrogen 0 “normal” hydrogen-stable isotope

Deuterium___________

1 Used to make “heavy water”

Tritium___________

2 Radioactive. Used to make “glow in the dark” sights for firearms and other items (not cheap stuff)

Atomic Weight

What is the atomic weight of H ?Isotope Symbol # of

NeutronsFractional (isotopic) Abundance

Hydrogen 0

Deuterium 1

Tritium 2

The Periodic Table

Groups, Periods, Main Group (A), Lanthanide & Actinide Elements, Metals, Non-Metals, Metaloids (semi-metals), Alkali Metals, Alkaline Earth Metals, Transition Elements (B), Halogens, Noble (“inert”) gases.

What is an allotrope?

Covalent Compounds• Compounds are formed when two or

more elements join in a defined ratio• Covalent compounds consist of

elements held together by covalent bonds– Covalent bonds are bonds where

electrons are shared between atoms– The atoms don’t have a positive of

negative charge on them• Some are named systematically, some

have long used “historical” names.

Empirical and Molecular Formula

• Empirical formula has the ratio of atoms correct, but not necessarily the absolute number of each

• HO• CF2

• Molecular formula has the absolute number of each atom in the molecule

• H2O2 (hydrogen peroxide)

• C2F4 (Teflon monomer)

Types of Molecular Models

Butanol• C4H10O1

– Formula

• Structural Formula

• Wedge and Dash

• Ball and Stick

Naming Covalent Compounds• Binary, non-metal compounds

– Name first element (use prefix if needed)

– Name second element, using a prefix if needed

• Some have historical names that are more commonly used

• H2O

• CO

• CO2

• UF6

• SiO2

• PF5

Naming Inorganic Acids (see trends?)(think about other names you may know for these)

Ions and Ionic Compounds• Atoms normally have zero net charge– # of electrons = # protons

• Ions have gained or lost electrons– Ions can form from any isotope– Ions have nothing to do with the nucleus, only the electrons.

Some Monoatomic Ions

What do the numbers mean?What is a cation? What is an anion?What trends or patterns do we see?Are these all the monoatomic ions there are?

Polyatomic Ions (covalently bonded atoms that carry a charge amongst the whole group)

Excuse me, Sir, but how many of these things are we going to have to know? My brain’s turning to Jell-O here!

Formulas and Naming Ionic Compounds

• Ions can have charge, but ionic compounds should have a net neutral charge

• One can have Empirical and Molecular Formulas for ionic compounds

• Instead of pre-fixes, IUPAC (International Union of Pure and Applied Chemistry) conventions are used.

• Naming…….• The name of the cation (+)

comes first.– If it has more than one

possible charge, that number comes next

• The name of the anion comes second.

• CaF2

• LiF

• Fe2O3

• Formulas– Remember, the charges MUST

balance.

• Use subscripts to make the charge balance.

• Calcium Chloride

• Zinc Sulfate

• Calcium Nitrate

• Magnesium Phosphate