4.2 Representing Molecular Compounds Part I

1. 4.2 4.2 Representing Molecular Compounds Part I

2. 4.2 Forming Molecular Compounds • Molecular Compounds (also known as covalent compounds are composed of two or more different non-metals • Molecular Compounds forms when atoms share a pair of electrons to form a covalent bond • In a covalent bond, the shared electrons are attracted to the nuclei of both atoms – this attraction holds the atoms together

3. 4.2 Covalent Compounds • Covalent compounds have varying degrees of solubility in water • Covalent compounds do not conduct electricity • Compared to ionic compounds, covalent compounds have much lower melting points

4. 4.2 1P0N 8P8N • Unlike an ionic bond in an ionic compound, electrons in a molecular compound are not transferred between atoms! – So the atoms remained uncharged • Like ionic bonds, covalent bonds happen since it brings the stability of a full outer energy level of electrons • Hydrogen • Oxygen • Like ionic bonds, covalent bonds can also be represented using Bohr-Rutherford diagrams and Lewis Dot Diagrams

5. 4.2 Ionic Bonding: - + K Cl K+ Cl- Covalent Bonding: • 2 Hydrogen atoms • Oxygen • H2O (H-O-H)

6. 4.2 Molecules • An ionic solid is composed of a repeating pattern of ions • Molecular compounds are composed of individual molecules – Each molecule is composed of a set number of atoms of each element

7. Molecular Compounds: B-R Diagrams • Bohr-Rutherford diagrams can be used to model molecular compounds • Example: Water (H2O) • 2 Hydrogen atoms • Oxygen • H2O (H-O-H)

8. Molecular Compounds: B-R Diagrams • Example: Carbon dioxide (CO2) • 1 carbon atom • CO2 • 2 oxygen atoms (O=C=O)

9. 1P0N 1P0N 7P7N 1P0N Molecular Compounds: B-R Diagrams H - H-N-H NH3

10. 4.2 Molecules • The term molecule is also used to describe two or more atoms of the same element joined by a covalent bond • These are known as diatomic molecules: H2, N2, O2, Cl2, Br2, I2 and F2 • “IBring Clay For Our New Home” • These diatomic molecules are not compounds since they only contain one type of atom!!

11. Molecular Compounds • When two non-metals bond they form a molecular compound, also called a molecule • Two non-metals cannot produce oppositely charged ions, they do not give and take electrons, instead they share electrons • This sharing of electrons creates a covalent bond • Covalent bond: a bond that results from the sharing of outer electrons between non-metals • When two atoms share a pair of electrons we can represent this with a dash between the two symbols • Ex: H - H, for H2 • When two atoms share two pairs of electrons we can represent this with a double dash between the two symbols • Ex: O = O, for O2 • Diatomic molecules: a molecule consisting of only two atoms of either the same or different elements

12. Properties of Molecular Compounds • When two atoms share two pairs of electrons we can represent this with a double dash between the two symbols • Ex: O = O, for O2 • Diatomic molecules: a molecule consisting of only two atoms of either the same or different elements • Soft • If they dissolve in water, they are not conductive • Low melting points • The same elements can combine in different ways to form different compounds • Ex: hydrogen and oxygen combine to form water (H20) and hydrogen peroxide (H2O2)

13. 4.2 1P0N 1P0N Molecules • How do diatomic molecules combine? (H2, N2, O2, Cl2, Br2, I2 and F2) 1P0N 1P0N . . . . H + H HH H-H

14. Molecules • How do diatomic molecules combine? (H2, N2, O2, Cl2, Br2, I2 and F2) O=O

15. Molecules • How do diatomic molecules combine? (H2, N2, O2, Cl2, Br2, I2 and F2) • How would you draw N2, Cl2, Br2, I2 and F2