Part 3 : Lewis Dot Structures and Multiple Bonds

1. COVALENT BONDING AND VSEPR Part 3: Lewis Dot Structures andMultiple Bonds

2. Objectives • To learn how to depict covalent bonds with Lewis Dot Structures • To understand the difference between single, double, and triple covalent bonds

3. Stability in Bonding H + H  H2 + energy atom atom molecule Molecule has less energy and is more stable than atoms

4. Ways to represent the hydrogen molecule: • H2 molecular formula - indicates number of atoms in molecule • H-H structural formula - dash is 1 SHARED pair of electrons • H:H dot structure (Lewis structure) - use 1 dot for each electron in highest energy level

5. Covalent Bonding • Covalent bonding is the sharing of electrons between atoms • Because of this, the atomic orbitals of atoms overlap one another

6. Orbital Overlap Crude picture representation: . . ATOMIC orbitals overlapping Refined picture representation: . . MOLECULAR orbital - holds 2 electrons maximum Orbitals can not overlap completely because of the 2 nuclei

7. Lewis Dot Structures of Covalent Compounds • Electrons of an atom are either core or valence electrons • Valence electrons are the outermost and involved in chemical reactions • They are shown in Lewis Dot structures

8. Valence Electrons • Valence electrons vary by element • Main Group element’s valence electrons are equal to their group number • Ex: Sodium (Na) belongs to Group 1A and therefore has 1 valence electron.

9. Let’s Do It!!! How many valence electrons does Potassium (K) have? 1 How many valence electrons does Antimony (Sb) have? 5 How many valence electrons does Phosphorus(P) have? 5 How many valence electrons does Magnesium (Mg) have? 2

10. Noble Gases • Noble Gases in Group VIIIA have either two valence electrons (He) or eight (Ne, Ar, Kr, Xe, and Rn) • They are extremely stable and this is the basis for the Octet Rule - elements react to attain the electron configuration of Group VIIIA

11. Neon has eight valence electrons, so its Lewis dot symbol is:

12. Octet Rule • Remember metals on the left of the periodic table tend to lose electrons and nonmetals on the right tend to gain • This is to achieve a stable configuration of 8 valence electrons

13. Covalent Bond • Each fluorine atom has seven valence electrons and require one more electron to satisfy the Octet Rule.

14. Covalent Bond • The left fluorine has a total of eight electrons and the right fluorine has a total of eight valence electrons • Nonmetallic elements react together and share electrons in order to obtain eight valence electrons

15. Covalent Bond • The two electrons in the covalent bond are often represented by a line • The F2 molecule can be represented using a line (bonding pair) and dots (six lone pairs)

16. Multiple Covalent Bonds • Some atoms have to share more than one electron in order to meet the Octet Rule • Each oxygen atom has six valence electrons and they each require two more electrons to satisfy the Octet Rule

17. Multiple Covalent Bonds • Both the left and right atoms now have a total of eight • Adouble bond is represented by two single lines and each represents two electrons

18. Covalent Bonds • Hydrogen is an exception to the Octet Rule because it only needs two electronsto be stable • H has one valence electron and it requires one more • F has seven valence electrons and it requires one more

19. Covalent Bonds • The hydrogen atom now has a total of two electrons around it and is stable • The fluorine atom now has a total of eight electrons around it and is stable

20. Objectives • To learn how to depict covalent bonds with Lewis Dot Structures • To understand the difference between single, double, and triple covalent bonds