Science Unit 5 Part 1

Review

• On the P.T., each column is called a group or family
• All elements in the same/ group have similar properties
• Atoms have p+, n0, e-
• Each element in a group has the same number of electrons in their outer orbital or shell
• The electrons in the outer shell are known as valence electrons
• The number of valence electrons determines how reactive an atom is

Stable Electron Configuration

• Atoms are not chemically stable until they have 8 valence electrons (octet rule)
• Hydrogen and Helium only need two
• Atoms will react to become stable - GAIN valence electrons or LOSE valence electrons
• A chemical bond is the force of attraction that holds two atoms together
• An electron dot diagram is a model of an atom in which each dot represents a v.e. (Known as Lewis Diagram)

Ionic Bonding

(Taken not shared)

• Electrons are transferred form one atom to another
• An ion is an atom that has a negative or positive electric charge
• An ion with a negative charge due to extra electrons is an anion
• An ion with a positive charge due to less electrons is a cation
• "Opposites attract"
• An ionic bond is the force that holds positive and negative ions together to form a compound that is electrically neutral

SET RATION THAT BALANCES OUT THE CHARGES IS THE GOAL

Ionic Compunds

• Compounds that contain ionic bonds are ionic compounds
  • Formed by metals (+charge) and non-metals (-charge)
• Polyatomic ions- ions that are made up of more than one atom but carry single charge
• A chemical formula is a notation that shows what elements and compounds contain and the ratio of the atoms or ions of these elements

1. Find charges of each atom
2. USe subscripts for a ration that equals zero (use the crisis cross or transfer of electrons method) 
3.  List positive ion first metal, then negative ion-(non-metal)
4. If negative ion is an element - change ending to ide
   1. If negative ion is polyatomic the name stays the same