chapter 6 chemical names and formulas. molecules and molecular compounds molecule - basic unit of a...
TRANSCRIPT
Chapter 6 Chemical Names and
Formulas
Molecules and Molecular Compounds
• Molecule - Basic unit of a compound
• Molecular Compound - a compound that is composed of molecules (two or more nonmetals)
Characteristics of Molecular Compounds
• Representative unit- molecule• Type of elements- nonmetals
ONLY• Physical state- solid, liquid or gas• Melting point- low
Ions and Ionic Compounds
o Ion- atoms or groups of atoms with a charge.
o Ions form when an atom or group of atoms gain or lose electrons
Atom – neutral particle# protons = # electrons
Ion – charged particle (lost or gained electrons)# protons ≠ # electrons
Atom vs. Ion
Charge = # of protons – # of electrons
3 – 3 = 0
This is an
ATOM
neutral
Find the charge…
Sodium Sodium atomatom
Sodium ionSodium ion
Protons: 11Electrons: 11Charge: 0
Protons: 11Electrons: 10Charge: +1
lost 1 electron
protons > electrons = + charge
Chlorine atomChlorine atom Chlorine ionChlorine ion
Protons: 17Electrons: 17Charge: 0
Protons: 17Electrons: 18Charge: -1
gained 1 electron
protons < electrons = – charge
Ions and Ionic Compounds
1. Cation - a positive ion formed when an atom loses electrons.
o A positive ion would have the same name as a normal atom
o BUT… they have the same name, they have different chemical properties
Example- Na and Na+
Sodium Atom Sodium Ion
Ions and Ionic Compounds
2. Anion- a negative ion formed when an atom gains electrons.
oThe name of an anion is changed to -ide
Example: Cl and Cl-
chlorine atom chloride ion
Characteristics of Ionic Compounds
Ionic compound- composed of metals and nonmetals (cations and anions)
• Ionic compounds are electrically neutral•The charges on the anions and cations in the
compound equal zero
• Representative Unit - formula unit• Type of elements – metals and nonmetals• Physical State - solids• Melting Point - high
• Chemical Formula - shows the kinds and numbers of atoms in the smallest representative unit of a substance
Examples: O2, N2
•Molecular Formula - shows the kinds and numbers of atoms in a molecule of a compound. (groups of nonmetals…molecular compounds)
Examples: CO2, H2O
• Formula Unit - lowest whole-number ratio of ions in an ionic compound. (metals and nonmetals…ionic compounds)
Examples: MgCl2, AlCl3
Representing Chemical Compounds
Is the compound ionic or molecular?
1. NaCl2. N2O
3. SO2
4. MgCl25. CCl2
Name each: atom or ion
1. Mg2. Li3. Mg+2
4. Li+1
5. Cl6. Br7. Cl-1
8. Br-1
Ionic Charges:
Ionic Charges
Transition Metals- can have more than one charge, a Roman numeral in parenthesis indicates the numerical value of the charge
Ionic Charges
Exceptions– Ag is always +1– cadmium and zinc are always +2
Practice: What is the charge of each ion typically formed by each element?
1. Sulfur2. Lead, 4 electrons lost3. Strontium4. Argon5. Bromine6. Copper, one electron lost
Need to look at the charges of both ions because the compound must be neutral. (overall charge = 0)
NaP
BrCaO Al
+1
-2 +3
+2 -1
-3
Crisscross the numbers and drop the charges
Na O+1 -2
2
Na2O
Al S+3 -2
2
Al2S3
3
Use parenthesis if you have more than one polyatomic ion (an ion with more than one atom)
Ca NO3
+2 -1
2
Ca(NO3)2
Mg PO4
+2 -3
3
Mg3(PO4)2
( ) 2( )
CO3( )
Reduce the subscripts if possible
Mg O+2 -2
2
MgO
2 Sn+4 -2
2
Sn(CO3)2
42
4. According to the information above, what is the chemical formula for
aluminum sulfate?
a. AlSO4
b. Al2(SO4)3
c. Al3(SO4)2
d. Al6SO4
Al3+ SO42-
5. What type of bond is formed between two potassium atoms and one sulfur atom?
a. Ionic Bondb. Metallic Bondc. Hydrogen Bondd. Covalent Bond