Chemical Bonding

Remember Chemical Bonding is a result of valence electrons being gained, lost, or shared between atoms Remember Chemical Bonding is a result of valence electrons being gained, lost, or shared between atoms There are primarily three types of bonding between atoms, ionic bonds, polar covalent bonds, and non-polar covalent bonds There are primarily three types of bonding between atoms, ionic bonds, polar covalent bonds, and non-polar covalent bondsionic bonds, polar covalent bonds, and non-polar covalent bondsionic bonds, polar covalent bonds, and non-polar covalent bonds

Types of Bonding The differences in electronegativity reflects the character of bonding between elements The differences in electronegativity reflects the character of bonding between elements

Chemical Bonding Most atoms have lower potential energy when they are bonded to other atoms than they have as they are independent particles Most atoms have lower potential energy when they are bonded to other atoms than they have as they are independent particles What does this mean? What does this mean? It means they “like to be bonded” It means they “like to be bonded”like to be bondedlike to be bonded

Covalent Bonds When two atoms form a covalent bond, their shared electrons form overlapping orbitals When two atoms form a covalent bond, their shared electrons form overlapping orbitals

Covalent Bonds

- water is a polar molecule because oxygen is more electronegative than hydrogen, and therefore electrons are pulled closer to oxygen.

Nobel Gases Nobel gasses are unreactive because they are very stable Nobel gasses are unreactive because they are very stable Other atoms do not have completely filled orbitals so they “want” to fill them with help from other atoms to become stable Other atoms do not have completely filled orbitals so they “want” to fill them with help from other atoms to become stablewant

Electron Dot Notation Electron-dot notation is an electron- configuration notation in which only the valence electrons of an atom of a particular element are shown indicated by dots placed around the element symbol Electron-dot notation is an electron- configuration notation in which only the valence electrons of an atom of a particular element are shown indicated by dots placed around the element symbol Electron-dot notation Electron-dot notation

Electron Dot-notation

Lewis Structures Electron dot notation is used to represent molecules Electron dot notation is used to represent molecules The pair of dots between the two symbols represents the shared electron pair of the hydrogen-hydrogen and fluorine-fluorine covalent bond H:H The pair of dots between the two symbols represents the shared electron pair of the hydrogen-hydrogen and fluorine-fluorine covalent bond H:H

Lewis Structures The pair of dots between the two symbols represents the shared pair of a covalent bond The pair of dots between the two symbols represents the shared pair of a covalent bond The unshared pair, the lone pair, is not involved in bonding and belongs just to that one atom The unshared pair, the lone pair, is not involved in bonding and belongs just to that one atom

Structural Formula The pair of dots represents a shared pair of electrons in a covalent bond is replaced by a dash: H-H The pair of dots represents a shared pair of electrons in a covalent bond is replaced by a dash: H-H A structural formula indicates the kind, number and arrangement, and bonds but not the unshared pairs of the atoms in a molecule: F-FH-Cl A structural formula indicates the kind, number and arrangement, and bonds but not the unshared pairs of the atoms in a molecule: F-FH-Cl

Structural Formulas A single covalent bond, or single bond, is a covalent bond in which one pair of electrons is shared between two atoms : Example: diatomic hydrogen H 2 : H-H A single covalent bond, or single bond, is a covalent bond in which one pair of electrons is shared between two atoms : Example: diatomic hydrogen H 2 : H-H A double covalent bond, or a double bond, is a covalent bond in which two pairs of electrons are shared between two atom A double covalent bond, or a double bond, is a covalent bond in which two pairs of electrons are shared between two atomdouble covalent bonddouble covalent bond Example: diatomic nitrogen N 2 : Example: diatomic nitrogen N 2 :

Structural Formulas A triple covalent bond, or simply a triple bond, is a covalent bond in which three pairs of electrons are shared between two atoms A triple covalent bond, or simply a triple bond, is a covalent bond in which three pairs of electrons are shared between two atoms –Example: ethyne C 2 H 2 : Multiple bonds, double and triple bonds, have greater bond energies and are shared in bond length, they are STRONG!! Multiple bonds, double and triple bonds, have greater bond energies and are shared in bond length, they are STRONG!! Multiple

Drawing Structures 1. Determine the type and number of atoms in the molecules. For example Draw the Lewis structure of iodomethane CH 3 I The formula shows 1 Carbon, 3 Hydrogens, and 1 Iodine

Drawing Structures 2. Write the electron-dot notation for each type of atom in the molecule. Place one electron dot on each side of the element before pairing any electrons. Carbon is in group 14, 4 valence electrons Iodine is in group 17, 7 valence electrons Hydrogen is in group 1, 1 valence electron

Drawing Structures 3. Determine the total number of valence electrons available in the atoms to be combined. C1 x 4e = 4e I1 x 7e = 7e 3H3 x 1e = 3e 3H3 x 1e = 3e 14e 14e

Drawing Structures 4. If carbon is present, it is the central atom, otherwise, the least electronegative atom is in the center. Hydrogen is never central

Drawing Structures 5. Add unshared pairs of electrons to each nonmetal atom (except hydrogen) such that each is surrounded by eight electrons. Distribute the electron dots so that each atom, except for hydrogen, beryllium, and boron, satisfies the octet rule. Change each pair of dots that represents a shared pair to one dash, two, or three dashes Distribute the electron dots so that each atom, except for hydrogen, beryllium, and boron, satisfies the octet rule. Change each pair of dots that represents a shared pair to one dash, two, or three dashes

Drawing Structures 6. Count the number of electrons surrounding each atom and check the number of valence electrons is the same number you started with in step 3.