Part 3: Lewis Dot Structures and Multiple Bonds COVALENT BONDING AND VSEPR Part 3: Lewis Dot Structures and Multiple Bonds

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

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

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

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

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

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

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.

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

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

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

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

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

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

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)

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

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

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

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

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