Unit 7 Section 2 Notes

Unit 7 Section 2 Notes

Ionic and Covalent Bonding Unit 7 Section 2 Notes 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. Atoms and Electrons Review of 4 Fundamental Forces

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 Atoms and Electrons Symbols of atoms with dots to represent the valence-shell electrons

1 2 13 14 15 H

16 17 18 He: Li Be

B C

Na Mg Al

N O

Si : F :Ne :

P S

:Cl :Ar :

Electron Dot Diagrams 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 Ionic Bonds I cant take this anymore

Ahh, I just lost an electron! Are you positive? Ionic Bonding: One big greedy thief dog!! Sodium atom Na 2-8-1

11 p+ 11 e0 e Sodium ion Na + 2-8 ( = Ne) 11 p+ 10 e1+

Formation of Sodium Ion Magnesium atom Magnesium ion Mg 2-8-2 12 p+ 12 e0 2e

Mg2+ 2-8 (=Ne) 12 p+ 10 e2+ Formation of Magnesium Ion Group 1

Group 2 H+ Mg2+ Li+ Ca2+ Na+

Sr2+ K+ Ba2+ Group 13 Al3+ Some Typical Ions with Positive Charges (Cations)

A. Number of valence electrons in aluminum a) 1 eb) 2 ec) 3 eB. Change in electrons for octet a) lose 3eb) gain 3 e- c) gain 5 eC. Ionic charge of aluminum a) 3b) 5c) 3+ Quick Quiz #1 A. Number of valence electrons in aluminum c) 3 eB. Change in electrons for octet a) lose 3eC. Ionic charge of aluminum

c) 3+ Quiz Quiz #1 Answers Give the ionic charge for each of the following: A. 12 p+ and 10 ea) 0 b) 2+ c) 2B. 50p+ and 46 ea) 2+ b) 4+ c) 4C. 15 p+ and 18ea) 3+ b) 3- c) 5- Quick Quiz #2 Give the ionic charge for each of the following: A. 12 p+ and 10 ea) 0 b) 2+ c) 2B. 50p+ and 46 ea) 2+ b) 4+ c) 4C. 15 p+ and 18ea) 3+ b) 3- c) 5-

Quick Quiz #2 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 Fions are needed to balance out the +2 charge so the particle is neutral Ionic Bonds Electricity: Solid ionic compounds dont conduct electricity When dissolved in water, ionic compounds conduct electricity because the ions are free to

move Ionic 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

Covalent Bonds Nonpolar Covalent Bond Note: Partial charges occur with polar

covalent bonds Polar Covalent Bond 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.

Covalent Bonds 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

Structural Formulas A polyatomic ion is an ion made of 2 or more atoms that are covalently bonded and that act like a single ion Polyatomic Ions BONDING SUMMARY How to tell what type of bond is holding a molecule together

Periodic Table NONMETAL METAL METAL + NONMETAL = IONIC NONMETAL + NONMETAL = COVALENT

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