Transcript You Try - mrsjohns
Learning Goals
Students will be able to understand the difference between ionic/ molecular compounds and acids Students will be able to name and write the chemical formula for all types of ionic/ molecular compounds and acids
Chemical Names and Formulas: Overview 1. Simple (Binary) Ionic Compounds (Metals and Non-Metals) 2. Compounds with Polyatomic Ions 3. Compounds with metals that can have multiple charges (Multivalent) a) using roman numerals (ie. copper (I) fluoride) b) using the classical system (ie. cuprous fluoride) 4. Molecular compounds (2 or more non-metals) 5. Acids a) Without oxygen b)With oxygen
1. Simple (Binary) Ionic Compounds (Pg. 68-73, 89-90) Form when a metal reacts with a non-metal Made up of cations (positive ions) and anions (negative ions) Attraction holding the ions together is called an IONIC BOND =
transfer
of electrons Ions are attracted to each other, and not directly attached Most form a crystal lattice structure (alternating ions extending in 3 dimensions)
Properties of Ionic Compounds -Ionic bonds are strong, therefore: -ionic compounds are hard, brittle solids -have a high melting point -Most are electrolytes (dissolve in water which surrounds each ion, causing the solution to conduct electricity)
NaCl dissociates (breaks into its parts) in water
Writing the Chemical Formula for Ionic Compounds
Chemical Formula
Definition: • shows the kind and numbers of atoms in the smallest whole number ratio of atoms in the substance Examples: MgO not Mg 2 O 2 , NaCl…
Ionic Compounds: NaCl (ratio of 1:1) -There is not 1 atom of Na, and 1 of Cl in NaCl -Remember: most ionic compounds are crystal lattice structures, so we just write the lowest ratio of atoms -So Na 368 Cl 368 would be just NaCl
Writing the Chemical Formula for Ionic Compounds (Cont’d) What is the formula for Magnesium Chloride?
Steps: 1)Write out the ions (Mg 2+ and Cl ) 2) Criss-Cross the superscript numbers (leave the + and – signs behind) so they become subscript #s on the opposite side MgCl 2 *Not Mg 1 Cl 2 : don’t include any # 1’s*
You Try:
What is the formula for aluminum oxide?
Al
2
O
3
*charges must balance so compound charge is neutral
Determining the name of Ionic Compounds What is the name of compound CaBr?
Steps: 1)Write out the name of the metal, calcium 2) Add the name of the non-metal second, bromine 3) Change the ending to ‘ide’ Calcium Bromide
You Try:
What is the name of Mg
3
N
2
Magnesium Nitride
2.Compounds with Polyatomic Ions (Pg. 94-95)
Polyatomic Ion: -an ion that consists of a stable group of 2 or more atoms acting together as a single charged particle -the ionic charge is shared over the entire ion, rather than being on just one atom
Writing the Chemical Formula for Compounds with Polyatomic Ions What is the formula for ammonium carbonate?
Steps: *you’ll know it involves polyatomic ions if the compound doesn’t end in ‘ide’ with the exception of hydroxide, cyanide & thiocyanide* 1)Write out the individual polyatomic ions as found on your green periodic table (NH 4 + and CO 3 2 ) 2) Put brackets around everything but the charges: (NH 4 ) + and (CO 3 ) 2 3) Criss-Cross the superscript numbers only (NH 4 ) 2 (CO 3 ) 4) Remove brackets that have an imaginary 1 behind them (NH 4 ) 2 CO 3
You Try:
What is the formula for Calcium chlorate?
Ca(ClO
3
)
2
* Remember, what happens in the brackets, stays in the brackets!
Determining the Name of Compounds with Polyatomic Ions What is the name of compound Mg 3 (PO4) 2 ?
Steps: 1)Write out the name of the first ion (magnesium) 2) Add the name of the second (polyatomic) ion (phosphate) 3) Leave the ending so it ends with ‘ate’ or ‘ite’ *with the exception of hydroxide, cyanide & thiocyanide* Magnesium Phosphate
You Try:
What is the name of Ca(HCO
3
)
2
Calcium Bicarbonate
3. Compounds with metals that can have multiple charges (Multivalent)
-
Many transition metals can have more than one stable ions that can form!
-That means the naming system for these compounds is a bit different.
-There are 2 ways of naming compounds with metals that have multiple ionic charges a) using roman numerals (ie. copper (I) fluoride) b) using the classical system (ie. cuprous fluoride)
Naming Compounds with ions that can have multiple charges using a) Roman Numerals Write the charge of the metal in roman numerals immediate after the metal FeCl 3 Iron (III) Chloride FeCl 2 Iron (II) Chloride
You Try:
What is the name of Fe
2
O
3
Iron (III) Oxide
*You know it must be Fe oxygen, Fe 2 O 3 formed 3+ because when it reacted with This 3 is how we know it is Iron (III)
Writing the formula for compounds with ions that can have multiple charges using Roman Numerals Name MnO 2 -Is the Manganese ion Mn 2+ or Mn 4+ ???
-We know Oxygen’s ion is O 2 , so if it bonded with Mn 2+ we would get Mn 2 O 2 , or MnO… so this one can’t be -Therefore, it must be Mn 4+ … So Manganese (IV) Oxide is correct
You Try:
What is the formula for SnO?
Tin (II) Oxide
*You know it must be Sn 2+ because its charge has cancelled with O 2-
Naming compounds with ions that can have multiple charges using: b) The Classical System The symbols of many elements are based on their latin names (Memorize these!!): Cu: Cuprous or Cupric Sn: Stannous or Stannic Pb: Plumbous or Plumbic Fe: Ferrous or Ferric Hg: Mercurous or Mercuric
b) The Classical System (Cont’d)
If the metal ends in ‘ous’ it is the ion with the lower charge If the metal ends in ‘ic’ it is the ion with the higher charge
Naming Using the Classical System
What is the classical name of Fe 2 O 3 ?
1) Find the charge of the metal… Fe 3+ or Fe 2+ ?
Fe 3+ 2) Fe 3+ is the higher charge, so it ends in ‘ic’ , therefore, the name must be… Ferric Oxide
You Try:
What is the classical name for SnO?
Stannous Oxide
*You know it must be ous because 2 + is lower than 4 +
4. Molecular Compounds (Pg. 97-98)
• composed of 2 or more non-metals • chemical formula gives EXACT number of atoms, rather than a ratio like within an ionic crystal • these elements are attached through a COVALENT BOND (
sharing
of outer electrons) • covalent bonds are strong
Determining the Formula of Molecular Compounds (Pg. 97-98)
• prefixes are used to name molecular compounds • tell us how many of each atom there are *Note: Never use mono as a prefix for the first element* Example: dinitrogen pentoxide di=2, pent=5 Therefore the formula is N 2 O 5
You Try:
What is the formula for oxygen difluoride ?
OF
2
Determining the Name of Molecular Compounds
Example: Nitrogen Triiodide
NI
3
You Try:
What is the name for PCl
5
?
Phosphorus Pentachloride
Diatomic Molecules
-formed by only 2 atoms (either the same or different) Example: HF: Has 1 covalent bond, is a molecular compound, and a diatomic molecule
7 Diatomic Elements -7 elements form diatomic molecules with themselves (H 2 , N 2 , O 2 , F 2 , Cl 2 , I 2 , Br 2 )
Mnemonic devices
If you highlight N, O, F, Cl, Br, I; six of the seven diatomic elements on a Periodic Table - they form the number 7. The 7th is hydrogen.
Use the acronym “I Bring Clay For Our New Home”: I = Iodine Bring = Bromine Clay = Chlorine For = Fluorine Our = Oxygen New = Nitrogen Home = Hydrogen
5) Naming Acids (Pg. 98-99)
All acids contain hydrogen (at the start) HCl hydrogen chloride or hydrochloric acid ???
If aqueous, HCl(aq), then it’s the acid What’s the difference between liquid and aqueous?...
Aqueous vs. Liquid?
An aqueous solution is a compound/element dissolved in water. A liquid is the compound/element in the liquid state.
Example: NaCl (aq) = this is a solution of sodium chloride dissolved in water NaCl (l) = this is molten salt. (>700 o C )
Hydrogen chloride
has the formula HCl. At room temperature, it is a gas, which forms hydrochloric acid upon contact with atmospheric humidity.
Naming Acids
(pg. 98-100) http://www.youtube.com/watch?v=27-aqIXf-Qg
a) Without Oxygen
Add the prefix ‘hydro’ and the ending ‘ic acid’ Example: HBr hydrobromic acid
You Try:
1. What is the name for HBr(aq)?
Hydrobromic acid 2. What is the name for HCN(aq)?
Hydrocyanic acid
Naming Acids
(pg. 98-100) http://www.youtube.com/watch?v=27-aqIXf-Qg
a) With Oxygen (Oxyacids)
Determine what ion it is made up of Example: H 2 SO 4 (aq): H + and (SO 4 ) 2 *sulfate ion* If the ion ends in ate, add the ending ic acid H 2 SO 4 = sulfuric acid
Naming Oxyacids
ate ic acid ite ous acid Example #2 : H 2 SO 3 (aq) Contains (SO 3 ) 2 *sulfite ion* H 2 SO 3 = sulfurous acid
You Try:
1. What is the name for HNO 3 (aq)?
Nitric Acid
2. What is the name for HNO 2 (aq)?
Nitrous Acid
Learning Goals
DID WE MEET THEM?
Can you: 1)recognize the difference between ionic and molecular compounds?
2) How is the naming system for molecular compounds different from ionic compounds?
3)How can you tell if the compound is an acid? How do we name them?