Formula Writing

Atoms can form ions by gaining or losing electrons. Metals tend to lose one or more electrons to form positive ions called cations. Cations are generally named by using the name of the parent atom. Copyright © Cengage Learning. All rights reserved

Nonmetals tend to gain one or more electrons to form negative ions called anions. Anions are named by using the root of the atom name followed by the suffix –ide. Copyright © Cengage Learning. All rights reserved

TYPES OF COMPOUNDS Molecular: composed of molecules. Contains two nonmetals and a covalent bond. (sharing electrons) Ionic: composed of ions. Contains metal-nonmetal and ionic bond. (transfer of electrons.)

Chemical Formula Composition Qualitative-which elements Number of atoms in a molecule Quantitative-how much Molecule: group of 2 or more atoms of the same element or group of atoms of different elements to form a compound.

MEMORIZE THESE!! Structural formula: shows how the atoms are joined. Empirical formula-smallest representative unit. Formula unit-the lowest whole number ratio of ions in an ionic compound Monatomic vs. Diatomic Elements: MEMORIZE THESE!! H2 N2 O2 F2 Cl2 Br2 I2

Ionic bonding Octet Rule: Atoms react by changing the number of electrons so as to acquire the stable electron configuration of a noble gas. Depends on the number of valence electrons. Lewis Dot Diagrams

Ions- atom or group of atoms that have a positive or negative charge. Cation: positively charged ion. Has lost electrons. Anion: negatively charged ion. Has gained electrons. Ionic bond is the force of attraction between oppositely charge ions.

IONIC CHARGES OF THE ELEMENTS Location on the periodic table. Transition metals can have multiple charges. (see page 130, Table 5-4) Polyatomic ions are a tightly bond groups that behave as a unit and carry a charge.

Names of Common Polyatomic Ions Copyright © Cengage Learning. All rights reserved

                                      

Fe+2, Fe+3 iron(II), iron(III) Fe+2, Fe+3 iron(II), iron(III) ferrous ferric Cu+1, Cu+2 copper(I), copper(II) cuprous cupric Hg+1, Hg+2 mercury(I), mercury(II) mercurous mercuric

Sn+2, Sn+4 tin(II), tin(IV) Sn+2, Sn+4 tin(II), tin(IV) stannous, stannic Pb+2, Pb+4 lead(II), lead (IV) plumbous, plumbic

NAMING IONIC COMPOUNDS Cation named first. Binary compounds: Two elements. Change the nonmetal ending to –ide. Ternary compound: name polyatomic ion. Some metals have more than one charge. Use –ous for lower charge. Use –ic for higher charge. Stock naming system uses Roman numerals to show charge on ion.

Molecular Compounds Covalent Bond sharing electrons between two nonmetals Use prefixes to designate number of atoms. Write the element name first. Change the ending of the second element to -ide.

Prefixes Used to Indicate Numbers in Chemical Names Copyright © Cengage Learning. All rights reserved

Flow Chart for Naming Binary Compounds Copyright © Cengage Learning. All rights reserved

Naming Acids Acids are ionic compounds that starts with H. Binary Acids The acid name begins with the prefix hydro-. The root of the anion is used and the –ide is changed to –ic. The word “acid” is used as the second word in the name.

Ternary Acids or Oxyacids Acids involving hydrogen and a polyatomic ion. When the anion ends in –ite, change the –ite ending on the stem to –ous. When the anion ends in –ate, change the –ate ending on the stem to –ic. The word “acid” is used as the second word in the name.

Relation of polyatomic ions Name depends on the number of oxygens. -ate is the higher number of oxygens. -ite is the lower number of oxygens. Per- is one oxygen more than –ate. Hypo- is one oxygen less than –ite.

Flowchart for Naming Acids Copyright © Cengage Learning. All rights reserved

Overall Strategy for Naming Chemical Compounds Copyright © Cengage Learning. All rights reserved

Ions combine to form ionic compounds. Properties of ionic compounds High melting points Conduct electricity If melted If dissolved in water Copyright © Cengage Learning. All rights reserved

Ionic compounds are electrically neutral. The charges on the anions and cations in the compound must sum to zero. Copyright © Cengage Learning. All rights reserved

Rules For Writing Ionic Compounds Write symbols of elements. Cation is first. Determine charge on ions. Select subscripts so the formula has zero total charge. Polyatomic ions do not break down under ordinary chemical reactions. When using subscripts with polyatomic ions, place formula ion in parentheses.

Criss Cross Method Numerical charge of each ion is crossed over and used as a subscript for the other ion. Signs of the number are dropped. Check for lowest whole number ratio.

                   

Hydrates Hydrates are ionic compounds that contain water. Name the ionic compound. Using the Greek prefixes, indicate the number of water molecules present. Ex. Zn(NO3)2 • 6 H2O zinc nitrate hexahydrate.