1. Ionic & Molecular Compounds Chapter 3 Section 3.1

2. Atom The smallest unit of an element that has the properties of that element

3. Ion An atom or group of atoms with a positive or negative charge

4. Anion A negatively charged ion An ion that has gained electrons

5. Cation A positively charged ion. An ion that has lost electrons.

6. Molecule A particle with no electric charge, formed by two or more atoms joined by covalent bonds.

7. Ionic Bond A chemical bond due to the attraction between oppositely charged ions

8. Binary Ionic Compound a compound composed of ions of two different elements; a positively charged metal ion and a negatively charged non- metal ion

9. Ionic Compound A compound composed of oppositely charged ions held together with ionic bonds.

10. Molecular Compound A compound formed when atoms of two or more different elements (usually non- metals) share electrons.

11. Binary Molecular Compound A compound composed of two different elements, usually two non-metals, that are joined together with covalent bonds.

12. Covalent Bond A chemical bond between atoms that share electrons

13. Compound A pure substance composed of two or more elements that are chemically combined in specific proportions.

14. 1. What two categories do chemists use to classify compounds? Include a description of how a compound is placed in each category in your answer. Compounds are placed into two categories; molecular compounds and ionic compounds. Molecular compounds are made up of atoms of non-metal elements that are held together by covalent bonds to form molecules. Ionic compounds are made up of oppositely charged ions (metals + non-metals) held together by ionic bonds. All compounds in each category will share similar properties.

15. 2. What type of compound is water and what is it composed of? Water is a molecular compound composed of two atoms of hydrogen and one atom of oxygen. The atoms are held together by covalent bonds which means that the hydrogen and oxygen atoms are sharing electrons.

16. 3. What analogy does the book use to describe covalent bonds? The book uses a tug of war analogy to describe how a covalent bond works. The rope represents the connection or bond between the atoms (teams) and keeps each atom (team) from coming together.

17. 4. Fully explain why most molecular compounds boil and melt at relatively low temperatures. Molecular compounds are held together by strong covalent bonds between the atoms. The covalent bonds that hold one molecule to another are weaker and can be broken much easier. The energy supplied during the melting process easily overcomes the weak covalent bonds holding the molecules together and therefore they will melt or boil at relatively low temperatures.

18. 5. Why are molecular compounds poor conductors of electricity and heat? Molecular compounds do not contain free electrons or ions and therefore are not good conductors of electricity or heat. Due to this characteristic they are very useful as insulators (i.e., covers for electrical wires).

19. 6. Use sodium chloride as an example to explain how ionic compounds form. Ionic compounds are formed when a cation (metal) gives up one or more electrons to an anion (non- metal). The bond that holds them together is a very strong bond known as an ionic bond. Sodium is a metal that forms cations and chlorine is a non-metal that forms anions. The sodium ion will give up its one valence electron to the chloride ion which needs one valence electron to fill its valence shell. An ionic bonds forms between the two ions and sodium chloride is formed.

20. 7. Describe the structure of ionic compounds. Ionic compounds form what are known as lattices; large structures with regular and repeating patterns.

21. 8. Fully explain why most ionic compounds boil and melt at very, very high temperatures. The ionic bonds that hold ionic compounds together are very, very strong, much stronger than covalent bonds. Due to the strength of the bonds, it takes a lot of energy to break the bonds and separate the ions. This means that ionic compounds have a tendency to melt or boil at very, very high temperatures (i.e., sodium chloride melts at 801°C)

22. 9. Explain why an ionic compound dissolved in water can conduct electricity while a solid cannot. In order to conduct electricity you need charged particles that can move. In a solid state, the charged particles of an ionic compound cannot move. However, if you dissolve an ionic compound in water or melt it, the ions are free to move around and can therefore conduct electricity.

23. 10. Explain how an ionic compound can be composed of charged particles but the compound itself has no overall charge. Ionic compounds are composed of negatively and positively charged ions that are attracted to one another. When the ionic bonds form between the ions, the charges cancel each other out and the overall compound has no charge. For example, a sodium ion has a charge of positive 1 and a chlorine ion has a charge of negative 1. When they combine, the charges cancel one another and the compound has no overall charge.

24. 11. An element in Group 1 (alkali metals) on the periodic table forms ionic compounds with elements in Group 17 (halogens) in a 1:1 ratio. What ratio would you expect elements from Group 2 (alkaline earth metals) and elements from Group 16 to have when they from ionic compounds? Explain your answer. Alkali metals and halogens form ionic compounds in a 1:1 ratio because the metals have a charge of +1 and the halogens have a charge of -1. Based on this fact, we can expect the alkaline earth metals and the group 16 elements to form compounds in a 1:1 ratio as well because alkaline earth metals have a charge of +2 and the group 16 elements have a charge of -2.