Chemical Bonds
What does the word BOND mean to you?
Chemical Bond attractive force between atoms or ions in a molecule or compound. Formed by: transferring e - (losing or gaining) sharing e -
What do you think a Chemical Formula is?
Chemical Formulas chemical formula elements that make up a compound exact number of atoms of each element in a unit of the compound Example : H 2 O H for the element hydrogen O for the element oxygen subscript number 2 written after the H for hydrogen What do you think the 2 means?
Formulas Subscript means written below subscript - how many atoms of that element are in a unit of the compound
Lesson Check How many hydrogen atoms are present in one molecule of ammonium acetate, NH C H O? 4 2 3 2 How about Carbon atoms? How about Oxygen atoms? Nitrogen? Hydrogen?
Why do you think the Nobel gases are stable? (they don t bond with anything)
The Unique Noble Gases All Nobel gases are stable: They have FULL outer shells!
Stability Octet Rule most atoms form bonds in order to have 8 valence e- (This is important) full outer energy level like the Noble Gases! Ne Stability is the driving force behind bond formation!
Hydrogen Hydrogen - one electron in its lone energy level single dot - hydrogen s outer energy level is not full. stable when it is part of a compound (when it has a full outer shell)
Helium helium s - two electrons in outer shell Contains full outer energy level by itself chemically stable Helium rarely forms compounds
Other Elements look at the elements in Groups 1, 2, and 13 through 17, what do you notice about their outer shell?
Outer Levels Getting Their Fill Why do atoms want to fill their outer shell with electrons? To become STABLE! How do elements trying to become stable, gain or lose their outer electrons? by combining with other atoms that also have partially complete outer electron shells.
To achieve Stability, atoms will: Transferring e - Ionic Bond Sharing e - Covalent Bond
Lesson Check What is a chemical bond? the force that holds atoms together in a compound What is an ion? (REVIEW) An atom with an unequal number of electrons and protons, giving the atom a charge How do atoms achieve stability? By gaining, losing, or sharing electrons Why do atoms gain or lose electrons? To achieve STABILITY
The Ionic Bond Ionic bond - attraction between opposite charges of ions in an ionic compound Transfer of electrons takes place.
Ionic Bonds NO NET CHARGE on compound
What kind of elements (metals, nonmetals, metalloids) do you think bond ionically? Ionic bonds - formed by bonding between metals and nonmetals.
Outer Electron shells i.e. sodium and chlorine. Getting Their Fill When they bond, sodium loses one electron and chlorine gains one electron.
Chemical bonds change properties of elements compound has properties that different than individual elements Sodium chloride Na (metal) Cl (gas)
Ionicly Bonded Compounds NaF NaCl TiO 2
Potassium Iodine
Potassium Iodide - KI Used in nutritional supplements to prevent iodine deficiency
Magnesium Chlorine (gas)
Magnesium Chloride- MgCl 2 Used to prepare tofu and soymilk
You Try It How does the ionic bond form between: Potassium and Bromine? Magnesium and Chlorine? Sodium and Fluorine? How would you write the compound?
Ionic Bonding Practice
Sharing Electrons Covalent bonding Some elements don t like to lose or gain electrons. Look at Carbon Look at Hydrogen What do you notice about the number of electrons in their valence shell?
Sharing Electrons Stability gained by sharing electrons, not by losing or gaining electrons.
Covalent bond forms when atoms share electrons Molecule achieves stability What is the substance called if it is formed via an ionic bond????
Look at Carbon, how many electrons does it need to fill its outer shell? Look at Hydrogen, how many electrons does it need to fill its outer shell? How would these two bond?
Carbon has 4 valence electrons, it needs 4 to fill its outer shell Hydrogen as 1, needs 1 to fill its outer shell 4 Hydrogen will share their electrons with Carbon, filling carbon s outer shell Carbon will share its 4 electrons, 1 for each Hydrogen The result is a covalent bond
Lesson Check - Bonding How would you draw the following molecules (show the electron dot structure): Chlorine and Chlorine? Phosphorus and Hydrogen? Silicon and Hydrogen?
What kind of elements (metals, nonmetals, metalloids) do you think bond covalently? Look at the periodic table which elements need less than 3 or 4 electrons to fill their valence shell? Covalent bonds - formed by bonding between nonmetals and nonmetals.
A single covalent bond is made up of two shared electrons. Energy Level is stable for each atom
Multiple Bonds more than one pair of electrons Example Nitrogen (N 2 ). 3 Pairs of electrons Triple Bond
Let s Try It! How would you draw the following molecules (show the electron dot structure): Carbon and Oxygen? Chlorine and Chlorine? Hydrogen and Carbon? Phosphorus and Hydrogen? Iodine and Iodine? Hydrogen and Oxygen? C H?
You Try It! Covalent Bonding Practice
Ionic vs. Covalent Lab
Unequal Sharing in Covalent Bonds Electrons are not always shared equally in covalent bond. Due to: Size of atom (sound familiar?) Charge of nucleus Total number of electrons in atom (sound familiar?)
Hydrogen Chloride -HCl Which attracts electrons more Hydrogen or Chlorine?
Polar Covalent Molecule
Polar Covalent Molecule Charge is neutral, but not equally distributed Slightly positive end, slightly negative end
Chlorine gas Cl 2 Do you think Chlorine gas is a polar molecule?
Nonpolar Covalent Molecule
Nonpolar Covalent Molecule Charge is neutral, electrons shared equally O 2 No oppositely charged ends
How do you tell if a molecule is Polar or Nonpolar? CO? Linear, so one will always attract electrons more than another HCl? Anytime there is one Hydrogen, it will be polar (hydrogen is weak!) Molecules with Oxygen, Nitrogen? Because these atoms attract electrons with a lot of strength, they are always polar Cl 2? Diatomic, always nonpolar C 2 H 2? Most carbon containing molecules are nonpolar
Review - Ionic vs. Covalent
Review - The Ionic Bond Attraction between 2 oppositely charged Ions transferring e - from a metal to a nonmetal
Review - Covalent Bond Attraction between neutral atoms Sharing of e - between two nonmetals
Review - Nonpolar Covalent Bond e - are shared equally usually identical atoms
Review - Polar Covalent Bond e - are shared unequally between 2 different atoms partial opposite charges + -
Review - Covalent Bond Nonpolar Polar Ionic
Review - Ionic or Covalent? IONIC BONDS Metallic and Non-Metallic (NaCl, NaF) COVALENT BONDS Non-Metal and Non-Metal (CO 2, SiBr 4 )
You Try It! Covalent bonding polar, nonpolar