Presentation on theme: "Compounds & Molecules NaCl, salt Buckyball, C 60."— Presentation transcript:
Compounds & Molecules NaCl, salt Buckyball, C 60
Compounds & Molecules COMPOUNDS are a combination of 2 or more elements in definite ratios by mass.COMPOUNDS are a combination of 2 or more elements in definite ratios by mass. The character of each element is lost when forming a compound.The character of each element is lost when forming a compound. MOLECULES are the smallest unit of a compound that retains the characteristics of the compound.MOLECULES are the smallest unit of a compound that retains the characteristics of the compound.
ELEMENTS THAT EXIST AS MOLECULES Allotropes of C
ELEMENTS THAT EXIST AS POLYATOMIC MOLECULES White P 4 and polymeric red phosphorus S 8 sulfur molecules
Molecular Compounds Compounds without Ions CH 4 methane CO 2 Carbon dioxide BCl 3 boron trichloride
MOLECULAR FORMULAS Formula for glycine is C 2 H 5 NO 2Formula for glycine is C 2 H 5 NO 2 In one molecule there areIn one molecule there are –2 C atoms –5 H atoms –1 N atom –2 O atoms
STRUCTUAL FORMULAS Can also write glycine formula as –H 2 NCH 2 COOH to show atom ordering structural formulaor in the form of a structural formula
MOLECULAR MODELING Ball & stick Space-filling Drawing of glycine
Naming Elements & Compounds Chapter 2 & 3: Chemical Equations Handbook BCl 3 boron trichloride CO 2 Carbon dioxide molecules are formed from two or more nonmetals. Ionic compounds have a cation and anion: generally involve a metal and nonmetal, NaCl ammonium chloride, NHCl ammonium chloride, NH 4 Cl
IONS AND IONIC COMPOUNDS IONS are atoms or groups of atoms with a positive or negative charge.IONS are atoms or groups of atoms with a positive or negative charge. Taking away an electron from an atom gives a CATION with a positive chargeTaking away an electron from an atom gives a CATION with a positive charge Adding an electron to an atom gives an ANION with a negative charge.Adding an electron to an atom gives an ANION with a negative charge.
Forming Cations & Anions A CATION forms when an atom loses one or more electrons. An ANION forms when an atom gains one or more electrons Mg --> Mg 2+ + 2 e- F + e- --> F -
CATION + ANION ---> COMPOUND COMPOUND CATION + ANION ---> COMPOUND COMPOUND Are NEUTRAL. Compounds have EQUAL number of + EQUAL number of + and - charges. Are NEUTRAL. Compounds have EQUAL number of + EQUAL number of + and - charges. COMPOUNDS FORMED FROM IONS Na + + Cl - --> NaCl
Properties of Ionic Compounds Forming NaCl from Na and Cl 2 A metal atom can transfer an electron to a nonmetal.A metal atom can transfer an electron to a nonmetal. The resulting cation and anion are attracted to each other by electrostatic forces.The resulting cation and anion are attracted to each other by electrostatic forces.
Electrostatic Forces The oppositely charged ions in ionic compounds are attracted to one another by ELECTROSTATIC FORCES. These forces are governed by COULOMB’S LAW.
Electrostatic Forces COULOMB’S LAW Direct relationship between charge and force: charges increase, the force increases. Inverse relationship between distance between ions and force: increase distance, decrease force. increase distance, decrease force.
Importance of Coulomb’s Law NaCl, Na + and Cl -, m.p. 804 o C MgO, Mg 2+ and O 2- m.p. 2800 o C
PREDICTING ION CHARGES In general metals (Mg) lose electrons ---> cationsmetals (Mg) lose electrons ---> cations nonmetals (F) gain electrons ---> anionsnonmetals (F) gain electrons ---> anions
METALS M ---> n e- + M n+ where n = periodic group Na + sodium ion Mg 2+ magnesium ion Al 3+ aluminum ion Transition metals --> M 2+ or M 3+ are common Fe 2+ iron(II) ion Fe 3+ iron(III) ion
NONMETALSNONMETALS NONMETAL + n e- ------> X n- where n = 8 - Group no. C 4-,carbide N 3-, nitride O 2-, oxide S 2-, sulfide F -, fluoride Cl -, chloride Group 7AGroup 6A Group 4A Group 5A Br -, bromide I -, iodide
Charges on Common Ions +3 -4-2-3 +1 +2 By losing or gaining e-, atom has same number of e-’s as nearest Group 8A atom.
Binary Ionic Compounds Mn 2+ + O 2- ----> MnO manganese (II) oxide Al 3+ + S 2- ----> Al 2 S 3 aluminum sulfide Sn 4+ + Cl - ----> SnCl 4 Tin (IV) chloride or Stannic chloride calcium fluoride Ca 2+ + 2 F - ---> CaF 2
Practice Name & Formulas Ultimate Equation Handbook Only the binary compounds Exercise 2-1 pg. 10 Exercise 3-2 pg 17 Homework: Worksheets pgs 23-28
POLYATOMIC IONS Groups of atoms with a charge. MEMORIZE the names and formulas in Table 3.1, page 89.