Naming Compounds and Writing Formulas. Periodic Table. Recall that the periodic table is more than a list of elements. Elements are put in columns because of similar properties. Each column is called a group. Representative Elements. 0. 1A. 4A. 6A. The group A elements. 2A. 3A. 5A.
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Periodic Table • Recall that the periodic table is more than a list of elements. • Elements are put in columns because of similar properties. • Each column is called a group.
Systematic Naming • There are too many compounds to remember the names of them all. • A compound is made of two or more elements. • The name should tell us how many and what type of atoms.
Types of Compounds • There are two types of compounds: ionic compounds and molecular compounds.
Ionic Compounds • The simplest ratio of the ions represented in an ionic compound is called a formula unit. • The overall charge of any formula unit is zero. • In order to write a correct formula unit, one must know the charge of each ion.
Atoms and Ions • Atoms are electrically neutral. • They have the same number of protons and electrons. • Ions are atoms, or groups of atoms, with a charge. • Ions have a different numbers of electrons.
Anions • An anion is a negative ion. • An anion has gained electrons. • Nonmetals can gain electrons. • The charge is written as a superscript on the right. F-1 Has gained one electron O-2 Has gained two electrons
Cations • A cation is a positive ion. • It is formed by losing electrons. • There are more protons than electrons. • Metals form cations. K1+ Has lost one electron Ca2+ Has lost two electrons
Ionic Compounds • The charges of monatomic ions, or ions containing only one atom, can often be determined by referring to the periodic table or table of common ions based on group number. • The charge of a monatomic ion is equal to its oxidation number.
Charges on Ions • For most of the Group A elements, the Periodic Table can tell what kind of ion they will form from their location. • Elements in the same group have similar properties, including the charge when they are ions.
Naming Cations • We will use the systematic way. • For cations, if the charge is always the same (Group A) just write the name of the metal.
Naming Cations • Transition metals (as well as tin and lead) can have more than one type of charge. • Indicate the charge with Roman numerals in parenthesis. • Zinc (Zn2+) and silver (Ag1+), although transition metals, only have one possible charge. Roman numerals ARE NOT used for zinc and silver.
Example • Li1+ • Li is the symbol for lithium. • Lithium is a Group 1A metal, so the charge is always the same. Write the name of the metal. • Li1+ is called the Lithium ion.
Example • Sr2+ • Sr is the symbol for strontium. • Strontium is a Group 2A metal, so the charge is always the same. Write the name of the metal. • Sr2+ is called the Strontium ion.
Example • Fe2+ • Fe is the symbol for iron. • Iron is a transition metal, so the charge is not always the same. Write the name of the metal, indicating the charge with Roman numerals in parenthesis. • Fe2+ is called the Iron (II) ion.
Example • Pb2+ • Pb is the symbol for lead. • Lead is a Group 4A metal, and the charge is not always the same. Write the name of the metal, indicating the charge with Roman numerals in parenthesis. • Pb2+ is called the Lead (II) ion.
Problem • Name the following cations. • Ca2+ Calcium ion Aluminum ion • Al3+ Tin (IV) ion • Sn4+
Problem • Name the following ions. • Na1+ Sodium ion Iron (III) ion • Fe3+ Copper (I) ion • Cu1+
Writing the Formulas for Cations • Write the formula for the metal. • If a Roman numeral is in parenthesis use that number for the charge. Indicate the charge with a superscript.
Writing the Formulas for Cations • If no Roman numeral is given, find the Group A metal on the periodic table and determine the charge from the column number.
Example • Nickel (II) ion • Ni is the symbol for nickel. • Nickel is a transition metal, which is the reason why the charge with Roman numerals in parenthesis was included. • The formula for the nickel (II) ion is Ni2+.
Example • Gallium ion • Ga is the symbol for gallium. • Gallium is a Group 3A metal and its charge is always the same (+3). • The formula for the gallium ion is Ga3+.
Problem • Write the formulas for the following cations. Mg2+ • Magnesium ion Cu2+ • Copper (II) ion • Potassium ion K1+
Problem • Write the formulas for the following ions. • Silver ion Ag1+ • Chromium (VI) ion Cr6+ • Mercury (II) ion Hg2+
Naming Anions • Naming monatomic anions is always the same. • Change the element ending to – ide • Example: F1- • F is the symbol for fluorine, F1- is fluor ide. ine.
Example • Cl1- • Cl is the symbol for chlorine. • Chlorine is a Group 7A nonmetal, so the charge is always the same (-1). • Cl1- is called the chloride ion.
Example • O2- • O is the symbol for oxygen. • Oxygen is a Group 6A nonmetal, so the charge is always the same (-2). • O2- is called the oxide ion.
Problem • Name the following anions. • S2- sulfide ion • Br1- bromide ion • N3- nitride ion
Problem • Name the following anions. • As3- arsenide ion • Te2- telluride ion
Writing the Formulas for Anions • Write the formula for the nonmetal. • Find the Group A nonmetal on the periodic table and determine the charge from the column number.
Problem • Write the formulas for the following anions. • iodide ion I1- • phosphide ion P3-
Problem • Write the formulas for the following anions. • selenide ion Se2- • carbide ion C4-
Ionic Compounds • Oxidation numbers can be used to determine the chemical formulas for ionic compounds. • If the oxidation number of each ion is multiplied by the number of that ion present in a formula unit, and then the results are added, the sum must be zero.
Ionic Compounds • In the formula for an ionic compound, the symbol of the cation is written before that of the anion. • Subscripts, or small numbers written to the lower right of the chemical symbols, show the numbers of ions of each type present in a formula unit.
Binary Ionic Compounds • Binaryionic compounds are composed of a metal bonded with a nonmetal. • Name the metal ion using a Roman numeral in parenthesis if necessary. • Follow this name with the name of the nonmetal ion.
Example • Name the following binary ionic compounds. • NaCl Sodium chloride • Ca3P2 Calcium phosphide
Example • Name the following binary ionic compounds. • CuO Copper (II) oxide • SnBr2 Tin (II) bromide
Problem • Name the following binary ionic compounds. • Fe2S3 Iron (III) sulfide • AlF3 Aluminum fluoride
Problem • Name the following binary ionic compounds. • KCl Potassium chloride • Na3N Sodium nitride
Problem • Name the following binary ionic compounds. • CrN Chromium (III) nitride • PbO2 Lead (IV) oxide
Writing Formulas for Binary Ionic Compounds • Write the symbol for the metal. Determine the oxidation number from either the column number or the Roman numeral and write it as a superscript to the right of the metal’s symbol.
Writing Formulas for Binary Ionic Compounds • To the right of the metal’s symbol, write the symbol for the nonmetal. Determine the oxidation number from the column number and write it as a superscript to the right of the nonmetal’s symbol.
