1). Ionic bond electron from Na is transferred to Cl. Na is a metal and Cl is a nonmetal

Transcription

1 Chemical Bonds

2 1). Ionic bond electron from Na is transferred to Cl. Na is a metal and Cl is a nonmetal

3 Salt versus Molecules A metal cation and nonmetal anion are joined together by an ionic bond called SALT A group of atoms joined together by a covalent bond is called a MOLECULE A Compound is a group of two or more elements bonded together (Ionic or Covalent).

4 Monatomic vs. Diatomic Molecules Most molecules can be monatomic or diatomic Diatomic Molecule is a molecule consisting of two atoms There are 7 diatomic molecules (SUPER 7) N 2, O 2, F 2, Cl 2, Br 2, I 2, H 2 You can also remember them as: H 2 O 2 F 2 Br 2 I 2 N 2 Cl 2

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6 Bonds in all the polyatomic ions and diatomics are all covalent bonds

7 Covalent Bonding! Electronegativity is the ability for an atom to attract an electron! Due to electronegativity the sharing of electrons can be unequal. Nonpolar covalent equal sharing Polar covalent unequal sharing

8 Covalent Bonds

9 Molecular Compounds aka covalent compounds aka molecular covalent Covalent Bonds are atoms held together by SHARING electrons between NONMETALS

10 Properties of Molecular Compounds Liquids or gases at room temperature Lower Melting Points than Ionic Compounds (which means that they are weaker than ionic)

11 Molecular Formulas The Molecular Formula is the formula of a molecular compound It shows how many atoms of each element a molecule contains Example H 2 O contains 3 atoms (2 atoms of H, 1 atom of O) C 2 H 6 contains 8 atoms (2 atoms of C, 6 atoms of H)

12 Practice How many atoms total and of each do the following molecular compounds contain? 1. H 2 2. CO 3. CO 2 4. NH 3 5. C 2 H 6 O

13 Practice: True or False 1. All molecular compounds are composed of atoms of two or more elements. 2. All compounds are molecules. 3. Molecular compounds are composed of two or more nonmetals. 4. Atoms in molecular compounds exchange electrons. 5. Molecular compounds have higher melting and boiling points than ionic compounds.

14 Ionic versus Covalent IONIC COVALENT Bonded Name Salt Molecule Bonding Type Transfer e - Share e - Types of Elements Metal & Nonmetal Nonmetals Physical State Solid Solid, Liquid, or Gas Melting Point High (above 300ºC) Low (below 300 ºC) Solubility Dissolves in Water Varies Conductivity Good Poor

15 Chapter 8.2 Covalent Bonding Remember that ionic compounds transfer electrons in order to attain a noble gas electron configuration Covalent compounds form by sharing electrons to attain a noble gas electron configuration Regardless of the type of bond, the Octet Rule still must be obeyed (8 valence electrons)

16 Single Covalent Bond A Single Covalent Bond consists of two atoms held together by sharing 1 pair of electrons (2 e - )

17 Electron Dot Structure

18 Double Covalent Bonds Sometimes atoms attain noble gas configuration by sharing 2 or 3 pairs of electrons A Double Covalent Bond is a bond that involves 2 shared pairs of electrons (4 e - )

19 Triple Covalent Bond A Triple Covalent Bond is a bond that involves 3 shared pairs of electrons (6 e - )

20 Covalent Bonds

21 Polar Bonds and Molecules There are two types of covalent bonds Nonpolar Covalent Bonds (share equally) Polar Covalent Bonds (share unequally)

22 Polar Covalent A Polar Covalent Bond is unequal sharing of electrons between two atoms (HCl) In a polar covalent bond, one atom typically has a negative charge, and the other atom has a positive charge

23 Nonpolar Covalent Bond A Nonpolar Covalent Bond is equal sharing of electrons between two atoms (Cl 2, N 2, O 2 )

24 Classification of Bonds You can determine the type of bond between two atoms by calculating the difference in electronegativity values between the elements Type of Bond Electronegativity Difference Nonpolar Covalent 0! 0.4 Polar Covalent 0.5! 2.1 Ionic 2.1! 4.0

25 Example 1 A) Ionic or covalent? B) Draw the Lewis Structure C) Determine electronegativity difference and polarity Cl 2

26 Example 2 A) Ionic or covalent? B) Draw the Lewis Structure C) Determine electronegativity difference and polarity H 2 O

27 Example 3 A) Ionic or covalent? B) Draw the Lewis Structure C) Determine electronegativity difference and polarity PF 3

28 Example 4 A) Ionic or covalent? B) Draw the Lewis Structure C) Determine electronegativity difference and polarity NaCl

29 Naming acids If the anion attached to hydrogen ends in -ide, put the prefix hydroand change -ide to -ic acid HCl - hydrogen ion and chloride ion hydrochloric acid H 2 S hydrogen ion and sulfide ion hydrosulfuric acid

30 Naming Acids If the anion has oxygen in it, then it ends in - ate of -ite change the suffix -ate to -ic acid (use no prefix) HNO 3 Hydrogen and nitrate ions Nitric acid change the suffix -ite to -ous acid HNO 2 Hydrogen and nitrite ions Nitrous acid

31 HF H 3 P H 2 SO 4 H 2 SO 3 HCN H 2 CrO 4 Name these Hydrofluoric acid Hydrophosphoric acid Sulfuric acid Sulfurous acid Cyanic acid Chromic acid

32 Writing Acid Formulas Hydrogen will always be first name will tell you the anion make the charges cancel out. Starts with hydro?- no oxygen, - ide no hydro?, -ate comes from -ic, - ite comes from -ous

33 Write formulas for these hydroiodic acid HI acetic acid HC 2 H 3 O 2 H carbonic acid 2 CO 3 HPO 3 phosphorous HBr acid hydrobromic acid