1. Ionic Compounds

2. An element’s atoms need to acquire 8 valence electrons in order to be stable like a noble gas. (except for hydrogen and helium which only need 2) Elements can do this by gaining and losing electrons or by combining with other elements. When an atom gains or loses electrons, it’s called an ion.

3. If an element loses electrons, it will have a positive charge and be called a cation. Group 1 elements will lose one electron and have a +1 charge. Group 2 elements will lose two electrons and have a +2 charge. Group 13 elements will lose three electrons and have a +3 charge.

4. If an element gains electrons, it will have a negative charge and be called an anion. Group 15 elements will gain three electrons and have a – 3 charge. Group 16 elements will gain two electrons and have a – 2 charge. Group 17 elements will gain one electron and have a – 1 charge.

5. A monatomic ion is a one- atom ion, so it just has one element. Examples: Mg 2+ or Br - or Na +

6. The electrostatic force that holds oppositely charged particles together in an ionic bond is referred to as an ionic bond. Ionic bonds usually occur between a metal and a nonmetal. Ionic bonds between metals and oxygen are called oxides. Ionic bonds between metals and halogens are called halides or salts.

7. Melting point, boiling point, and hardness are physical properties that depend on how strongly the particles are attracted to each other.

8. When energy is absorbed during a chemical reaction, the reaction is endothermic. When energy is released during a chemical reaction, the reaction is exothermic. The formation of ionic compounds from positive and negative ions is always exothermic.

9. The simplest ratio of the ions represented in an ionic compound is called a formula unit. For example, the formula KBr represents a formula unit for potassium bromide because potassium and bromide ions are in a one-to-one ratio. The formula MgCl2 represents magnesium chloride because there are two chloride ions for every one magnesium ion. The overall charge for a formula unit is always zero.

10. Metals do not bond with each other in ionic bonds. When metals come together to form a solid, the electron sea model suggests that they contribute their valence electrons to form a “sea” of electrons. The electrons are not held by one specific atom and are free to move, so they are called delocalized electrons. A metallic bond is the attraction of a metallic cation to delocalized electrons.

11. The physical properties of metals can be explained by metallic bonding. Most metals have high melting and boiling points. Metals are malleable (can be hammered into sheets) and ductile (can be drawn into wire). Metals are good conductors of heat and electricity.

12. An alloy is a mixture of elements that has metallic properties. Alloys most commonly form when the elements involved are either similar in size or the atoms of one element are considerably smaller than the atoms of the other.