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Lab #4 Periodic Table – Part 2. Chemistry 108. Instructor: Robert Goldman. Periodic Trends – Electronegativity. Electronegativity is the attraction an atom has for its bonding valence electrons. Electronegativity increases from left to right and from bottom to top of the periodic table. - PowerPoint PPT Presentation
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Lab #4Periodic Table – Part 2
Chemistry 108
Instructor:Robert Goldman
Periodic Trends – Electronegativity
Electronegativity is the attraction an atom has for its bonding valence electrons.
Electronegativity increases from left to right and from bottom to top of the periodic table.
Periodic Trends – Electronegativity
Periodic Trends – Electronegativity
The amount of energy required to remove a valence electron from an atom.
More electronegative atoms have higher ionization energies.
Periodic Trends – Ionization energy
Periodic Trends – Atomic size
Atomic size tends to increase LEFT to RIGHT across the periodic table and from TOP to BOTTOM down groups.
This is due to valence electrons occupying shells further from the nucleus.
Periodic Trends – Atomic size
Periodic Trends – Bonding Patterns
Elements usually form a certain number of bonds, depending on their location in the periodic table.
Group 14 elements (C, Si, Ge, Sn, Pb) tend for form 4 bonds.
For each group you move right, the normal number of bonds formed decrease by one.
Periodic Trends – Bonding Patterns
Therefore…– Group 14 elements tend to form 4 bonds.– Group 15 elements tend to form 3 bonds.– Group 16 elements tend to form 2 bonds.– Group 17 elements tend to form 1 bond.– Group 18 elements (noble gases) tend not to form
any bonds (stable). Hydrogen forms only one bond.
Chemical Nomenclature
You are expected to be able to provide appropriate names for simple binary and ternary compounds.
Binary = Two elements Ternary= Three elements
Naming Binary Compounds
Binary compounds begin with names based on the most metallic element present in the compound.
Ex. NaCl – sodium is more metallic than chlorine, so “sodium” is the first part of the name of this compound.
Naming Binary Compounds
Next, the name of the less metallic element is added, with a suffix of –ide.
Ex. chlorine becomes chloride
Overall name of compound is sodium chloride.
Naming Binary Compounds
How would you name the following?
– K2S
– MgO
Naming Binary Compounds
Binary compounds can also form from two non-metals.
In this case, the name of the most metallic element (lowest in electronegativity) is used as the first part of the compound name.
Naming Binary Compounds
When two non-metals combine, they can form several different compounds.
Unique names are assigned to distinguish these.
Remember these important prefixes!!!
1= mono 4= tetra
2= di 5= penta
3= tri 6= hexa
Naming Binary Compounds
Example– Phosphorous and chlorine combine to form PCl3
and PCl5.
– In order to distinguish between the two: PCl3 is called phosphorous trichloride
PCl5 is called phosphorous pentachloride
Naming Binary Compounds
How would you name the following?
– SiO2
– MgO4
IMPORTANT
DO NOT use these prefixes for compounds formed between a metal and a non-metal.
LiF is lithium floride NOT lithium monoflouride!
Naming Binary Compounds
Compounds containing transition elements (center of the periodic table, no group #’s) are a bit different.
Most have a valence of two and form two bonds (+2 ion) by losing two electrons.
They may, however, form other ions by losing different numbers of electrons.
Naming Binary Compounds
The charge of the transition element must always be shown in the name of the compound.
This is done by adding the charge in roman numerals in parenthesis after the ion.
Ex: Iron (II) oxide – Iron with TWO BONDS
Naming Binary Compounds
So…– How many bonds does copper form in copper (II)
chloride? Cu forms one bond, Cl forms one bond-- CuCl
– What is the charge on titanium in titanium (IV) oxide?
Ti forms four bonds in this case, O (group VI) forms two bonds– TiO2
Naming Ternary Compounds
Ternary compounds contain three different elements.
Naming Ternary Compounds
Many of these are acids or salts of acids. Salt= compound formed from an acid + a base
– A salt is formed when the hydrogen from an acid is replaced by a metal.
Memorize the following acids:HClO3 =chloric acid HBrO3=bromic acid
HIO3=iodic acid H2CO3=carbonic acid
H2SO4=sulfuric acid H3PO4=phosphoric acid
HNO3=nitric acid (P. 94 in your textbook)
Naming Ternary Compounds
Chloric acid trends– HClO4 = perchloric acid (1 extra oxygen)
– HClO3 = chloric acid (base acid)
– HClO2 = chlorous acid (1 less oxygen)
– HClO = hypochlorous acid (2 less oxygens)
This is on P. 95 in your textbook.
Naming Ternary Compounds
Example:– HIO3 is iodic acid
– HIO2 becomes iodous acic
– Etc…
Naming Ternary Compounds
To name a salt of a ternary acid…– 1. Name the metal that replaced the hydrogen.– 2. Name the acid that the salt is derived from but
change the suffix to show the compound is no longer an acid (-ic becomes –ate,-ous becomes –ite).
Ex. LiNO3 has a base acid of HNO3 (nitric acid)– The salt will then be named lithium nitrate.
Naming Ternary Compounds
If an acid has two hydrogens, both are replaced to form a salt.
Group I metals replace one hydrogen each. Ex: Na2SO4 (derived from H2SO4)
– Name= sodium sulfate
Naming Ternary Compounds
Group II metals will replace two hydrogens each.
CaSO4 (derived from H2SO4)– Name=calcium sulfate
Today in lab…
We will be determining the percent water in a hydrated salt by weighing before and after dehydrating it.
Follow directions in lab manual. Be careful with hot crucibles! WEAR GOGGLES AT ALL TIMES! Let me know if you have questions.