Two types of chemical bonds are Ionic Bonds and Covalent Bonds Chemical Bonding: Covalent Bonding

Chemical Bonds Two types of chemical bonds are Ionic Bonds and Covalent Bonds

Covalent Bonding  The chemical bond formed when two atoms share electrons  Covalent means “share” Way to remember: “CO” – together like a couple or companion Way to remember: “VALENT”– valence electrons  What is the difference between a covalent bond and an ionic bond?  Electron sharing occurs when atoms such as Hydrogen bond to other nonmetals or with the same element

Covalent Bonding  By sharing electrons, each atom has a stable set of eight  The force that holds atoms together in a covalent bond is the attraction of each atom’s nucleus for the shared pair

Covalent Bonding: Molecules  What is a molecule?  Neutral group of atoms joined by covalent bonds  Ex. 2 Fluorine atoms form a Fluorine molecule

Covalent Bonding  Except for Hydrogen, the number of covalent bonds that nonmetal atoms can form equals the number of electrons needed to make a total of eight  Ex. Nitrogen has 5 valence electrons and Hydrogen has 1 valence electron

Covalent Bonding  Double bonds are when two atoms share two pairs of electrons  Ex. CO2  Triple bonds are when atoms share three pairs of electrons  Ex. Nitrogen  What is the difference between a double bond and a triple bond?  A double bond shares 4 electrons and a triple bond shares 6 electrons

Covalent Bonding: Molecular compounds  What is a molecular compound?  A molecular compound is a compound that is composed of molecules  The molecules of a molecular compound contain atoms that are covalently bonded  What are the properties of molecular compounds?  Low melting points and boiling points  Do not conduct electricity when dissolved in water

Covalent Bonding: Molecular Compounds  What is unequal sharing of electrons?  Atoms of some elements pull more strongly on shared electrons than do atoms of other elements  As a result, the electrons are pulled more towards one atom, causing the bonded atoms to have slight electrical charges which are not as strong as the charges on ions

Covalent Bonding Polar Bonding  A covalent bond in which electrons are shared unequally  The unequal sharing of electrons is enough to make the stronger pull slightly negative and the weaker pull slightly positive  Ex. H2O Nonpolar Bonding  A covalent bond in which electrons are shared equally  If two atoms pull equally on the electrons, neither atom becomes charged  Ex. F2

Covalent Bonding: Bonding in Metals  What is an alloy?  Mixture made of two or more elements that has the properties of a metal  In every alloy, at least one of the elements is a metal  Alloys are generally stronger and less likely to react with water than are the pure metals from which they are made

Covalent Bonding: Metallic Bonding  What is a metallic bond?  An attraction between a positive metal ion and the electrons surround it  Metals are in group 1, 2, and 3 so they lose electrons easily because their valence electrons are not strongly held  Each metal ion is held by a metallic bond  The more valence electrons an atom can add, the stronger the metallic bond will be

 ADD THE FOLLOWING NOTES TO YOUR PREVIOUS COVALENT BOND NOTES.  YOU WILL WRITE DOWN THE FOLLOWING NOTES. THEY ARE NOT FILL-IN-THE-BLANK.  YOU MAY HAVE TO USE A NEW SHEET OF PAPER.

Covalent Bonding  Attraction between neutral atoms  Formed by sharing e - between two nonmetals Cl

Covalent Bonding  Covalent bonds result in discrete molecules Cl 2 H2OH2O NH 3

Nonpolar Covalent Bonds  e - are shared equally  usually identical atoms  Ex: Carbon Dioxide Covalent Bonding (-) (+) (-) Opposite pulling cancels out CO 2

Polar Covalent Bonds  e - are shared unequally between 2 different atoms  results in partial opposite charges  Ex: Water Covalent Bonding H2OH2O (-) (+)

Covalent Bonding Sharing Electrons:

H2OH2O 2 hydrogen atoms 1 oxygen atom Shows: 1) elements in the compound 2) ratio of their atoms Covalent Bonding

Nonpolar Polar Ionic Covalent Bonding

Ionic and Covalent Bonds Comparison Chart IONIC COVALENT Electrons Melting Point Soluble in Water Conduct Electricity Other Properties transferred from metal to nonmetal high yes (solution or liquid) yes crystal lattice of ions, crystalline solids shared between nonmetals low no usually not molecules, odorous liquids & gases