1. Molecular Compounds

2. Objectives Distinguish between the melting points and boiling points of molecular compounds and ionic compounds Distinguish between the melting points and boiling points of molecular compounds and ionic compounds Describe the information provided by a molecular formula Describe the information provided by a molecular formula

3. Important Vocabulary Covalent bond Covalent bond Molecule Molecule Diatomic molecule Diatomic molecule Molecular compound Molecular compound Molecular formula Molecular formula

4. Molecules Matter takes many forms in nature Matter takes many forms in nature Noble gas elements exist as single atoms (monatomic) Noble gas elements exist as single atoms (monatomic) Some atoms of elements form salts that are crystalline solids with high melting points Some atoms of elements form salts that are crystalline solids with high melting points Many atoms form molecules, which are neutral groups of atoms joined together by covalent bonds Many atoms form molecules, which are neutral groups of atoms joined together by covalent bonds A covalent bond is formed when two atoms share electrons A covalent bond is formed when two atoms share electrons

5. Sharing Electrons Takes place between neutral atoms within covalent compounds Takes place between neutral atoms within covalent compounds Attractive and repulsive forces must be equal for a bond to form Attractive and repulsive forces must be equal for a bond to form The simplest example of this is found in diatomic molecules, which are molecules consisting of two atoms The simplest example of this is found in diatomic molecules, which are molecules consisting of two atoms For example: HI BrONClF For example: HI BrONClF

6. Molecular Compounds Molecular compounds are composed of molecules Molecular compounds are composed of molecules The molecules of a given molecular compound are all the same The molecules of a given molecular compound are all the same For example: water (dihydrogen oxide) & carbon monoxide For example: water (dihydrogen oxide) & carbon monoxide They are also known as covalent compounds because they form covalent bonds They are also known as covalent compounds because they form covalent bonds

7. Molecular Compound Properties Molecular compounds tend to have relatively lower melting and boiling points Molecular compounds tend to have relatively lower melting and boiling points Most are liquids or gases at room temperature Most are liquids or gases at room temperature Most molecular compounds are composed of atoms of two or more nonmetals Most molecular compounds are composed of atoms of two or more nonmetals

8. Ionic Compounds vs. Covalent Compounds Ionic Compounds Made of ions Made of ions Held together by ionic bonds or metallic bonds Held together by ionic bonds or metallic bonds Composed of a metal with a non-metal or 2 or more metals Composed of a metal with a non-metal or 2 or more metals Covalent Compounds Made of molecules Made of molecules Held together by covalent bonds Held together by covalent bonds Electrons are shared Electrons are shared Composed of 2 or more non-metals Composed of 2 or more non-metals

9. Molecular Formulas A molecular formula is the chemical formula of a molecular compound A molecular formula is the chemical formula of a molecular compound A molecular formula shows how many atoms of each element a molecule contains A molecular formula shows how many atoms of each element a molecule contains For example: A water molecule consists of 2 hydrogen atoms and 1 oxygen atom, so its molecular formula is H 2 O For example: A water molecule consists of 2 hydrogen atoms and 1 oxygen atom, so its molecular formula is H 2 O Molecular formula does not tell you the arrangement of the atoms in the molecule Molecular formula does not tell you the arrangement of the atoms in the molecule

10. Practice How many atoms of each? How many atoms of each? 1.C 2 H 6 2.CO 2 3.CCl 4