Unit 7 Section 2 Notes
Ionic and Covalent Bonding
Atoms and Electrons
» Atoms bond when their valence electrons interact˃Atoms with full outermost energy
levels are not reactive (Noble Gases)
Atoms and Electrons
» Atoms bond when their valence electrons interact˃Atoms with full outermost energy
levels are not reactive (Noble Gases) ˃Atoms with partially filled energy
levels are more reactive (Groups 1-17)» Goal of atoms: have a full octet (Follow
Octet Rule)
Atoms and Electrons
» Octet Rule: atoms tend to gain, lose, or share electrons so they have 8 electrons in their outer shell.
» By completing their octet (either gaining or losing electrons), atoms achieve “Noble Gas Status” and have the electron configuration of a noble gas.
Atoms and Electrons
» The positively charged nucleus attracts the negatively charged electrons; this electrostatic force holds 2 atoms together.
» Recall: The strong nuclear force is responsible for holding an ATOM together.
Review of 4 Fundamental Forces
Atoms and Electrons
» Electrons are placed in shells according to rules:˃1st shell: can hold up to 2 electrons˃2nd shell: can hold up to 8 electrons˃3rd shell: can hold up to 18
electrons, but after 8, you move to the 4th shell
Electron Dot Diagrams
Symbols of atoms with dots to represent the valence-shell electrons
1 2 13 14 15 16 17 18H He: Li Be B C N O : F :Ne :
Na Mg Al Si P S :Cl :Ar :
Ionic Bonds
» Ionic Bond: formed when metals react with nonmetals; electrons are transferred
» Metals lose electrons to form POSITIVELY charged ions, or cations˃ Examples: Lithium (Li), Sodium(Na),
Beryllium (Be), Magnesium (Mg)» Positive ions form when the number of
electrons are less than the number of protons˃ Group 1 metals → ion+1
˃ Group 2 metals → ion+2
˃ Group 13 metals → ion+3
“Ahh, I just lost an electron!”
“Are you positive?”
“I can’t take this anymore”
Ionic Bonding: One big greedy thief dog!!
Formation of Sodium Ion
Sodium atom Sodium ion Na – e Na +
2-8-1 2-8 ( = Ne)
11 p+ 11 p+
11 e- 10 e-
0 1+
Formation of Magnesium Ion
Magnesium atom Magnesium ion
Mg – 2e Mg2+
2-8-2 2-8 (=Ne)
12 p+ 12 p+
12 e- 10 e-
0 2+
Some Typical Ions with Positive Charges (Cations)
Group 1 Group 2 Group 13
H+ Mg2+ Al3+
Li+ Ca2+
Na+ Sr2+
K+ Ba2+
Quick Quiz #1
A. Number of valence electrons in aluminuma) 1 e- b) 2 e- c) 3 e-
B. Change in electrons for octeta) lose 3e- b) gain 3 e- c) gain 5 e-
C. Ionic charge of aluminum a) 3- b) 5- c) 3+
Quiz Quiz #1 Answers
A. Number of valence electrons in aluminum
c) 3 e-
B. Change in electrons for octeta) lose 3e-
C. Ionic charge of aluminum c) 3+
Quick Quiz #2
Give the ionic charge for each of the following:A. 12 p+ and 10 e-
a) 0 b) 2+ c) 2-
B. 50p+ and 46 e-a) 2+ b) 4+ c) 4-
C. 15 p+ and 18e-a) 3+ b) 3- c) 5-
Quick Quiz #2
Give the ionic charge for each of the following:A. 12 p+ and 10 e-
a) 0 b) 2+ c) 2-
B. 50p+ and 46 e-a) 2+ b) 4+ c) 4-
C. 15 p+ and 18e-a) 3+ b) 3- c) 5-
Ionic Bonds
» Nonmetals gain electrons to form NEGATIVELY charged ions, or anions˃ Examples: Oxygen (O), Sulfur (S),
Fluorine (F), Chlorine (Cl)» Negative ions form when the number of
electrons is more than the number of protons˃ Group 15 nonmetals → ion-3
˃ Group 16 nonmetals → ion-2
˃ Group 17 nonmetals → ion-1
Ionic Bonds
» Electrons are transferred in ionic bonding˃One atom gains electrons (typically
nonmetals), and the other atoms loses electrons (typically metals)
Ionic Bonds
» Example: Sodium loses one electron to get a +1 charge (Na+). Chlorine gains an electron to get a -1 charge (Cl-). Then, the oppositely charged ions attract each other and form a bond.
Ionic Bonds
Ionic Bonds
» Ionic compounds are in the form of network structures; they therefore have high melting and boiling points because of the high amount of energy required to pull apart the bonds
Ionic Bonds
» Ratio of Ions ˃The chemical formula NaCl tells us
there is 1 Na+ ion and 1 Cl- ion, forming a neutrally charged particle. +Since there is only one atom of each
element, there is a 1:1 ratio˃The chemical formula CaF2 tells us
there is 1 Ca+2 ion and 2 F- ions. 2 F- ions are needed to balance out the +2 charge so the particle is neutral
Ionic Bonds
»Electricity:˃Solid ionic compounds don’t
conduct electricity˃When dissolved in water, ionic
compounds conduct electricity because the ions are free to move
Covalent Bonds
» Covalent Bond: a bond formed when atoms share one or more pair of electrons˃Often made of molecules˃Formed between nonmetal atoms
Covalent Bonds
» There are 2 types of covalent bonds:˃ Nonpolar covalent bonds: electrons are
shared equally; often occurs between 2 atoms of the same element (diatomic molecules)
˃ Polar covalent bonds: electrons are shared unequally; often occurs between 2 atoms of different elements; shared electrons are attracted to the nucleus of 1 atom more than the other
+ Usually, electrons are more attracted to atoms of elements located to the right and closer to the top of the periodic table
Nonpolar Covalent Bond
Polar Covalent Bond
Note: Partial charges occur with polar covalent bonds
Covalent Bonds
» Covalent bonds form molecules, which tend to have low melting and boiling points ˃This is because their structures often
do not form a crystal lattice» Covalent molecules do not conduct
electricity well.
Structural Formulas
» When writing structural formulas:˃1 line drawn indicates that atoms share
1 pair, or 2 electrons+Example: Cl-Cl
˃2 lines drawn indicate that atoms share 2 pair, or 4 electrons+Example: O=O
˃3 lines drawn indicate that 3 pair, or 6 electrons are being shared
Polyatomic Ions
» A polyatomic ion is an ion made of 2 or more atoms that are covalently bonded and that act like a single ion
BONDING SUMMARYHow to tell what type of bond is
holding a molecule together Periodic Table
METAL + NONMETAL = IONICNONMETAL + NONMETAL = COVALENT
METALNONMETAL