Chemical Bonds
Chapter 6
6.1 Ionic Bonding
6.2 Covalent Bonding
Review of what you know
• An electron dot diagram is a model of an atom in which each dot represents a valence electron.
Notice dots for each family/group
Full energy levels
• When the outermost energy level of an atom is filled with electrons, the atom is stable and not likely to react.
• Nobel gases have stable electron configurations with eight valence electrons
Stable or not, Ions come!!
• Elements that do not have complete sets of valence electrons tend to react.
Ionic Bonding
• Some elements achieve stability through the transfer (give away) of electrons between atoms.
Ions Created
• View animation
Formation of Ions
• Ions are electrically-charged particles formed when atoms lose or gain electrons
• The charge on an ion is represented by a plus or a minus sign.
Cation – ion with a positive charge
Anion – ion with a negative charge
Did it Get or Give an Electron?
Fe+3 Cu+
Give Give
Did it Get or Give an Electron?
Sn+2
Get Give
Br-
Ionization Energy
• An electron can move to a higher energy level when an atom absorbs energy.
• The energy allows electrons to overcome the attraction of the protons in the nucleus.
• The amount of energy used to remove an electron is called ionization energy.
• It varies from element to element. • The lower the ionization energy, the easier
it is to remove an electron from an atom.
Remember Reactivity Demo?
Covalent Bonding
• A chemical bond in which two atoms share a pair of valence electrons.
• When two atoms share one pair of electrons, the bond is called a single bond
More Single Bonds
Molecular Models
•
Double Bond
Double Bond shown in structural formula (not dots!)
What kind of bond?
Triple Bond
Molecule
• A neutral group of atoms that are joined together by one or more covalent bonds.
Chemical Formula
• Used to describe the molecules of an element as well as a compound.
• The element hydrogen has the chemical formula H2.
• The subscript 2 indicates that there are two atoms in a molecule of hydrogen.
F.Y.I.
Exam Question
Most elements are……