 Organization of electrons in energy levels  Each energy level can hold a certain number of electrons ◦ 1 st level=2 electrons ◦ 2 nd level=8 electrons ◦ 3 rd level=18 electrons ◦ 4 th level=32 electrons  Maximum number of valence electrons=8

 Highest occupied energy level of an atom is filled with electrons ◦ 8 electrons in the highest energy level signifies the atom is stable

 Noble gases are stable with 8 valence electrons  Usually do not react with other elements

 Atoms will gain or lose electrons to become stable ◦ All elements want to become stable like the noble gases ◦ A chemical bond forms between atoms to make a compound  2 types: Ionic and Covalent

 Have one, two, or three more electrons than they need in order to be stable ◦ Determined by number of valence electrons  In order to become stable, they can: ◦ Lose electrons, or ◦ Combine electrons with another metal

 Have less than the number of electrons they need in order to be stable ◦ Determined by the number of valence electrons  In order to become stable, they can: ◦ Gain electrons, or ◦ Share electrons with another nonmetal

 Model of an atom in which each dot represents a valence electron.  The symbol in the center represents the nucleus and all the other electrons in the atom.  Used when illustrating how atoms gain or lose electrons to achieve stability

 The transfer of electrons from one atom to another to achieve a stable electron configuration  Forms between a metal and a nonmetal  Metal will give away 1, 2, or 3 electrons to the nonmetal  Bond will form between the atoms and create a compound

 When an atom gains or loses an electron, the number of protons is no longer equal to the number of electrons. ◦ The atom is no longer neutral ◦ An Ion has formed  atom that has a net positive or negative electric charge  represented by a plus or minus sign

 Two types of ions: 1.Cation  ion with a positive charge, atom lost/donated electron(s)  Metals 2.Anion  ion with a negative charge, atom gained electron(s)  Nonmetals

 A sodium ion has 11 protons and 10 electrons. The sodium ion has a charge of 1+. The symbol for the ion is written Na 1+, or Na + for short.

 The ion that forms when a chlorine atom gains an electron has 17 protons and 18 electrons. This ion has a charge of 1–. The symbol for the ion is written Cl 1–, or Cl – for short.

 The amount of energy used to remove an electron  The lower the ionization energy, the easier it is to remove an electron from an atom.

 Compounds that contain ionic bonds  Represented by chemical formulas ◦ Notation that shows what elements a compound contains and the ratio of the atoms or ions of these elements in the compound ◦ EX: NaCl  From this you can tell there is 1 sodium ion and 1 chlorine ion  Ratio 1:1 ◦ EX: MgCl 2  The 2 is called a subscript, used to show how many atoms of that element are in a compound  1 magnesium ion and 2 chlorine ions  Ratio 1:2

 Example: ◦ When sodium reacts with chlorine, an electron is transferred from each sodium atom to a chlorine atom. ◦ Each atom ends up with a more stable electron arrangement than it had before the transfer.

 Example: ◦ Sodium transfers 1 valence electron to chlorine ◦ This gives chlorine 8 valence electrons

 Example: ◦ When the transfer occurs an ionic bond forms between the two atoms ◦ Sodium becomes positive because it lost an electron, so it is the cation ◦ Chlorine becomes negative because it gained an electron, so it is the anion

 Ionic compound would be: NaCl

 Example: ◦ Magnesium has 2 extra electrons…it will give these to chlorine so that chlorine can be stable ◦ An ionic bond forms ◦ Mg is cation with +2 charge because it gave away 2 electrons ◦ Cl is anion each with a -1 charge because each one received 1 electron

 Ionic compound would be: MgCl 2

1. Draw electron dot diagrams for each element, separate them with a plus sign. 2. Use arrows to show the transfer of electrons. Add metal(s) or nonmetal(s) if needed. ◦ Remove ALL valence electrons from metal. ◦ Add valence electrons to nonmetal until it has Draw yield sign (arrow). 4. Write the symbols of all of the elements on the right side of the arrow. Draw all valence electrons around the nonmetal(s). 5. Label the cation and the anion by assigning the correct charge to each. (Must equal zero). 6. Write the chemical formula for the compound.

 Examples: ◦ Na 2 S ◦ BeF ◦ K 3 P ◦ Li 2 O ◦ RbF ◦ AlCl 3

 All form crystals  Tend to have high melting and boiling points  Are very hard and very brittle  Conduct electricity when they dissolve in water

 Solids whose particles are arranged in a lattice structure

 I ons are arranged in an orderly, three- dimensional structure. Each ion is attracted to all the neighboring ions with an opposite charge. This set of attractions keeps the ions in fixed positions in a rigid framework, or lattice.