Unit+5+A

__Chapter 5__

Aguilar, Nichols, Kinard (We apologize for the superscript not working in the formulas)

Valence Electrons: -The number of electrons in the highest energy level. (the electrons in the highest s and p orbitals) -These electrons give properties to the compounds that the elecments form -Valence electrons will never exceed 8 -He has only 2 valence electrons yet it is full and does not bond well

Lewis Dot Structures: -A 3-D model to show how the valence electrons pair around the element -There can be 4 pairs of electrons, but the electrons don’t want to pair unless absolutely necessary

Octet Rule: -When bonds are formed they want to adhere to the Octet Rule= there are 8 electrons in the outer energy level of an atom classified as a noble gas elements have electrons to gain or lose to reach the stable octet based upon their Group on the periodic table

Ions: -When an element gains or loses an electron it becomes an ion. Elements do this to achieve the Noble Gas configuration (octet rule). These ions have different properties than the original element Cation- an element an element that has lost one or more electrons; typically a metal Anion- an element that has gained one or more electrons; typically a nonmetal

Examples: Cations (loses e-) Mg becomes Mg+2 (because it is easier to lose two e- than gain 6 e-) K becomes K+1 Aniona (gains e-) O becomes O-2 As becomes As-3

Naming Ions- Nomenclature: Monatomic ion- a cation or anion is formed from a single atom -Each ion is written with its symbol and a superscript to show its charge

Naming Cations: -Write the symbol of the element -Determine the number of electrons and write it as a superscript -Write the element name with the word “ion” following it Example: Magnesium- Mg+2 is magnesium ion

Naming Anions: -Drop the ending (last syllable) of the element and add “ide ion” to the name Example: Chlorine- Cl-1 is chloride ion

Naming Transition Metals: -transition metal ions vary from element to element -the only way to know the ion is to reference your chart and begin memorizing them Example: Copper(I)= Cu+2

Hydrates • Compounds that have water trapped in them • The water is trapped during a cooling process • Formula: CuSO4 •5H2O • Naming: Copper II Sulfate pentahydrate 1.) Naming the primary compound as we have been naming them: name the cation (Copper II) and the anion (sulfate) 2.) Tells you how many water molecules are in the compound. 2:di, 3:tri, 4:tetra, 5:penta, 6:hexa, 7:hepta 3.) Write hydrate for water

BaCl2•2H2O= Barrium dichlorate dihydrate MgCO3•5H2O= Mangnesium carbonate pentahydrate

% Composition of H2 O • You find the total atomic mass of the compound (all elements and water) • Take the mass of the water/total mass x 100% Sample: BaCl2•H2O • Ba: 137.3 g • Cl: 2 x 35.45= 70.9 g • H2O: 2 x 18.01= 38.02 • Total: 244.2 g • % H2O= (36.02/244.2) x 100= 14.75%

Sample problem-lab: • 10.407 g of hydrated barium iodide is heater and .877g of H2O is driven off. Assuming this is all of the water, what is it’s formula and name? • Answer: 0.877g H2O x (1 mol H2O/ 18.01 g)= 0.0493 mol H2O • 10.407 – 0.877= 9.53g BaI2 • 9.53g BaI2 x (1 mol/ 391.12 g)= 0.0244 mol • (0.0244/0.0244)= 1: (0.0493/0.0244)= 2 • BaI2•2H2O Barium Iodide dihydrate

Please enjoy this complimentary picture along with a repeat of the example problem