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Valence ElectronsElements with similar chemical behavior have the same
number of valence electrons.
For the representative elements (1A, 2A, 3A, 4A, 5A, 6A, 7A, 8A) the group number corresponds to the number of valence electron in each group (with the exception of He)
When examining electron configurations, the electrons that are present in the highest principle energy level represent the valence electrons of those atoms.
Br: [Ar]4s2 3d10 4p5 Bromine has 7 valence electrons
Valence Electrons and Electron Dot Structures
Valence electrons are the electrons that participate in chemical bonds
Electron dot structures consist of the atom symbol and its valence electrons represented as dots.
Br: [Ar]4s2 3d10 4p5
The Octet Rule - MetalsMetals tend to lose electrons to gain stability. When
they lose electrons they attain a stable electron configuration where the next lowest-energy level has a full octet.
The Octet Rule – Non-metalsNon-metals tend to gain electrons to obtain a full
octet in their highest occupied p sublevel
Properties of Ionic Compounds The chemical formula for an ionic compound is called a formula unit
which represents the lowest who number ration of atoms in that compound ( ex. NaCl)
Most ionic compounds are crystalline solids at room temperature
Ionic compounds generally have very high melting points
Ionic compounds can conduct electricity when molten or dissolved in water
Coordination Number = The number of ions of opposite charge surrounding the ion in a crystal.
Metallic Bonding
Positive metal ions floating in a sea of electrons.
• Metals are excellent conductors of electricity
• Metals can be easily deformed (They are malleable and ductile)
Know that metals are arranged in crystalline structures, but do not worry about the arrangement of these structures: face-centered, body-centered, hexagonal.
AlloysAlloys are mixtures of metalsProperties of alloys are usually superior to those of
their component elements.
Substitutional Alloy
Interstitial Alloy
Recalling the Periodic Table Metals
(Left)Nonmetals
(Right)Metalloids
(on line)
Physical State
Reflect light?
Malleability/Ductility: hammered/draw to wire?
Melting point
Conduct heat/electricity?
Solid (Except Hg)
Solid or Gas(Except Br)
Solid
Yes. If polished
No Some. If polished
Yes No Some
HighMany > 800oC
Low Various
Yes No Not well
Periodic Table Review
Groups- vertical columns within the periodic table
Representative elements- group “A” elements (columns1,2, 13-18 or s and p block elements)
Transition metals- group “B” elements (columns 3-12 or d block elements). Also include inner transition elements or f block elements.
Important families of elements Alkali Metals- metals in
group 1A that form +1 ions
Alkaline Earth Metals- metals in group 2A that form +2 ions
Halogens- nonmetals in group 7A that form -1 ions
Noble gases- Nonmetals located in far right column that are generally nonreactive
Atoms vs. Ions
Atom- NEUTRAL species with equal number of protons and electrons
Ion- CHARGED species with unequal number of protons and electrons Cation- (+) ion [lost electron(s)] Anion- (-) ion [gained electron(s)]
Compounds Compound- collection of atoms that is NEUTRAL overall
Molecular compound- composed of nonmetals Ionic compound- composed of cations and anions
(metal ions and nonmetal ions) in a crystal lattice
Interpreting Chemical Formulas Interpreting Formulas
Molecular formula- indicates type and amount of each atom in a compound
Diatomic molecules- Br I N Cl H O F exist as two atom molecules when ALONE! (Example: Br2)
Formula unit- lowest ratio of ions in an ionic compound (so that charge is zero)
Ratio of Atoms in a Compound Law of Definite Proportions Law of Multiple Proportions (Examples: FeCl2 FeCl3)
Writing Formulas of Molecular Compounds
Writing Formulas (Example: Carbon Dioxide)
More metallic element (or least electronegative)first (Ex: carbon before oxygen)
Write symbols for each element next to one another (Ex: CO)
Add subscripts to relate number of each atom in the molecule (Ex: CO2)
Greek Prefixes- KNOW: mono-, di-, tri-, tetra-, penta-, hexa-, hepta-, octa-, nona-, deca-
Naming Molecular Compounds
Naming Binary Molecular Compounds (Ex: SO3) Name in order appearing in formula
(Ex: sulfur oxygen)
Replace ending of last element with -ide (Ex: sulfur oxide)
Add prefixes to indicate number of each atom in molecule (Ex: sulfur trioxide) Note: mono is dropped if there is only one of the first atom. It is used if there is only one of the second atom. (example: CO is named carbon monoxide
Naming Ionic Compounds
Most cations are given the element’s nameExamples: NaCl = Sodium chloride
KCl = Potassium chloride
Monatomic anions end in –ide LiBr = Lithium bromide
MgS = Magnesium sulfide
Polyatomic ions usually end in –ate or –ite Exceptions: OH-1, CN-1, and NH4
+1
Writing Formulas of Ionic Compounds Writing Formulas of Ionic Compounds (Ex: sodium oxide)
Identify charge on metal and nonmetal ions- (Na+1, O2-) Criss-cross superscripts to balance charges (Na2O) Check if total formula has 0 charge
(2 Na ions @ +1) + (1 O ion @ -2) = 0 Write answer with subscripts (Na2O)
Note: Polyatomic (many atom) ions are written same except parenthesis are put around them if subscripts are added
Example: Magnesium hydroxide (Mg2+, OH1-) = Mg(OH)2
Stock System- transition metal ion charge
Some metals can exist in several forms (Ex: Cu+1, Cu+2)
Chemical formula used to decide which ion is present (Ex: CuCl2 – must be Cu+2)
When naming the ion the charge number is represented in roman numerals in parenthesis following the element name (Ex: copper (II) chloride)
** This is only done for elements that can have more than one possible charge. Refer to your ion table**
Acids Acids- form hydronium ions in water (H3O1+) Binary Acids contain H and one non-metal (HCl)
The names of binary acids always begin with hydro and are completed by dropping the ending of the nonmetal and adding -ic.
HCl = Hydrochloric Acid
•Oxyacids contain H and a polyatomic anion which contains oxygen•Oxyacids are named by dropping the –ate or –ite ending from the anion and adding –ic or –ous.
•H2SO4 = Hydrogen plus sulfate = sulfuric acid•H2SO3 = Hydrogen plus sulfite = sulfurous acid
Remember: If you “ate” acid, you might say “ic”!!