Period 4 Group 1 Characteristics of Chemical Bonds, Ions, and Ionic Compounds

Ionic Bonding - Formed from attraction among closely packed, oppositely charged ions -Ions are formed when an atom loses an electron to an atom that has a high affinity for electrons -Ionic compounds result between reaction of metals and nonmetals -Atoms are so different that one or more electrons are transferred to create attracted, oppositely charged ions.

The electrons of two hydrogen atoms (when close together) are attracted to what part of each atoms? When close together, the two electrons are simultaneously attracted to both nuclei.

 In covalent bonding, electrons are shared by nuclei equally.  Sometimes, atoms are not so different that electrons are completely transferred but are still different enough to form a polar covalent bond.  Polar covalent bonds – a covalent bond in which the electrons are not shared equally because one atom attracts the shared electrons more than the other atom. Covalent Bonding & Polar Covalent Bonds

 How are polar covalent bonds held together? Since the electrons do not share equally, one atom attracts the shared electrons more than the other atom, causing the bonds to hold together.

What is electronegativity? -The tendency of an atom in a molecule to attract shared electrons to itself

 -The higher the atoms’ electronegativity value, the closer the shared electrons tend to be to those atoms when it forms a bond.  Electronegativity is expressed on a periodic table as increasing left to right across a period, and decreasing down a group for the representative elements.

Explain how electronegativity and polarity are related. If atoms have very similar electronegativities, the electrons are shared almost equally and the bond show little polarity. If the atoms have very different electronegativity values, a very polar bond is formed.

 -Atoms in stable compounds almost always have a noble gas electron configuration  When representative metals & nonmetals react, they transfer electrons in such a way that both cation and anion have noble gas electron configurations.  -Chemical compounds are always electrically neutral  -Transition metals exhibit more complicated behavior in configuration.

 Answer:

 Structures of virtually all binary ionic compounds can be explained by a model that involves packing the ions as they were hard spheres.  The larger spheres, usually anions, are packed together and the small ions occupy the interstices of the model.  When metal loses all of its valence electrons to form a cation, it gets smaller; a cation is always smaller than the parent atom, and an anion is always larger than the parent atom. Structures of Ionic Compounds - Polyatomic ions with their opposite charges attract each other the same way as do the simple ions in binary ionic compounds. - Individual polyatomic ions are held together by covalent bonds, with all the atoms behaving as a unit. Ionic Compounds Containing Polyatomic Ions

What does the packing of ions represent? The larger spheres (usually the anions) are packed together, and the small ions occupy the interstices (spaces or holes) among them.

1. How would you obtain information about the strength of a bond? 2. What is the result of covalent bonding? 3. What if all the atoms had the same electronegativity? What if they all had very different electronegativities? 4. What happens when representatives of metals and nonmetals react? 5. What’s the size of the cation and the anion compared to the parent atom? 1. By measuring the energy required to break the bond: the bond energy. 2. The bonding results from mutual attraction of the 2 nuclei for the shared electrons. 3. The electrons are shared almost equally and bond shows little polarity; a very polar bond is formed. 4. They transfer electrons in such a way that both the cation and anion have noble gas electron configurations. 5. A cation is smaller than the parent atom; the anion bigger than the parent atom (cation < parent atom < anion)

 McDougal Littell, “World of Chemistry” pages (for images and information).         Hydrogen-fluoride-elpot-transparent-3D-balls.png Hydrogen-fluoride-elpot-transparent-3D-balls.png 