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 Ion- atoms or groups of atoms with a charge. Ions form when an atom or group of atoms gain or lose electrons

Atom vs. Ion Atom – neutral particle # protons = # electrons Ion – charged particle (lost or gained electrons) # protons ≠ # electrons What if... Note: can never lose or gain protons!

3 – 3 = 0 This is an ATOM Charge = # of protons – # of electrons Find the charge… 3 – 3 = 0 neutral This is an ATOM

protons > electrons = + charge lost 1 electron Sodium atom Sodium ion Protons: 11 Electrons: 11 Charge: 0 Protons: 11 Electrons: 10 Charge: +1 protons > electrons = + charge

protons < electrons = – charge gained 1 electron Chlorine atom Chlorine ion Protons: 17 Electrons: 17 Charge: 0 Protons: 17 Electrons: 18 Charge: -1 protons < electrons = – charge

Ions and Ionic Compounds 1. Cation - a positive ion formed when an atom loses electrons. A positive ion would have the same name as a normal atom 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. The 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

Representing Chemical Compounds 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

Is the compound ionic or molecular? NaCl N2O SO2 MgCl2 CCl2

Name each: atom or ion Mg Li Mg+2 Li+1 Cl Br Cl-1 Br-1

Ionic Charges: +1 +2 +3 +/-4 -3 -2 -1 skip a few Charge Varies

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? Sulfur Lead, 4 electrons lost Strontium Argon Bromine Copper, one electron lost

COMPOUNDS

Writing the formulas of an ionic compound IONIC COMPOUNDS Writing the formulas of an ionic compound Need to look at the charges of both ions because the compound must be neutral. (overall charge = 0) Find the charges of the following elements - -1 Na +1 Ca +2 Br -3 +3 P -2 O Al

Na O Al S Na2O Al2S3 Crisscross the numbers and drop the charges +1 -2 +3 -2 Na O Al S 2 2 3 Na2O Al2S3

( ) Mg ( ) Ca NO3 PO4 Ca(NO3)2 Mg3(PO4)2 Use parenthesis if you have more than one polyatomic ion (an ion with more than one atom) +2 -1 -3 ( ) Mg +2 ( ) Ca NO3 PO4 3 2 2 Ca(NO3)2 Mg3(PO4)2

Mg ( ) O Sn CO3 MgO Sn(CO3)2 Reduce the subscripts if possible -2 -2 +2 +4 ( ) O Sn CO3 2 2 2 4 2 MgO Sn(CO3)2

Al3+ SO42- According to the information above, what is the chemical formula for aluminum sulfate? AlSO4 Al2(SO4)3 Al3(SO4)2 Al6SO4

What type of bond is formed. between two potassium atoms and What type of bond is formed between two potassium atoms and one sulfur atom? Ionic Bond Metallic Bond Hydrogen Bond Covalent Bond