study guide

astudy guide answers

Sure, I'll provide brief answers to each of these questions.

1. Which electrons in the atom are responsible for all reactivity of an element and thus are used in bonding?
   The valence electrons (electrons in the outermost shell) are responsible for an atom's reactivity and are involved in bonding.

2. What is the overall charge for any compound?
   The overall charge for any compound is neutral. This is because the total positive charge (from cations) equals the total negative charge (from anions).

3. Describe the properties of a compound compared to those of the elements that make up the compound.
   Compounds often have different properties from the elements that compose them. For example, sodium (a metal) and chlorine (a gas) combine to form sodium chloride (a solid salt).

4. What are subscripts? What do the subscripts in a chemical formula represent?
   Subscripts are the small numbers written next to chemical symbols in a formula. They represent the number of atoms of each element in the compound.

5. What are the three types of bonds?
   The three types of bonds are ionic, covalent, and metallic.

6. How do atoms become chemically stable?
   Atoms become chemically stable by achieving a full outer electron shell, usually by gaining, losing, or sharing electrons.

7. How are ionic bonds formed?
   Ionic bonds are formed when one atom transfers electrons to another atom, resulting in oppositely charged ions that attract each other.

8. What does "electrons are transferred between atoms in a bond" mean?
   This means that one atom gives up electrons to another atom, creating positive and negative ions that are held together by electrostatic forces.

9. What are the characteristics for an ionic compound?
   Ionic compounds typically have high melting points, are soluble in water, and conduct electricity when dissolved or melted.

10. What is the single unit of an ionic compound called?
    The single unit of an ionic compound is called an ion pair or formula unit.

11. How are covalent bonds formed?
    Covalent bonds are formed when two atoms share electrons in order to achieve a stable electron configuration.

12. What is another name for a covalent compound?
    A covalent compound is also called a molecule.

13. What are the characteristics of a covalent compound?
    Covalent compounds have low melting points, are often gases or liquids at room temperature, and do not conduct electricity in any state.

14. What is a single unit of a covalent compound called?
    The single unit of a covalent compound is called a molecule.

15. What is another name for a covalent bond?
    Another name for a covalent bond is a molecular bond.

16. Be able to draw a Lewis dot diagram for ionic compounds, covalent compounds, and polyatomic ions.
    Lewis dot diagrams show valence electrons and bonding. For ionic compounds, show electron transfer. For covalent compounds, show electron sharing. Polyatomic ions have charges, so show extra or missing electrons.

17. For covalent bonds, be able to draw Lewis Dot Diagrams that require double and triple bonds.
    Double and triple bonds are shown by adding additional shared pairs of electrons. For example, oxygen (O₂) has a double bond.

18. In a Lewis dot diagram, how many dots (electrons) equal one bond? What can you use instead of the dots to represent a single bond?
    One bond equals two electrons. A single bond can be represented by a single line.

19. What is the difference between a polar covalent bond and a nonpolar covalent bond?
    In a polar covalent bond, electrons are shared unevenly, while in a nonpolar covalent bond, electrons are shared equally.

20. Be able to recognize examples of a polar covalent bond and a nonpolar covalent bond by looking at a diagram or using the Electronegativity value.
    In polar bonds, the atoms have different electronegativities (greater than 0.4 difference). Nonpolar bonds occur when electronegativities are equal or very similar.

21. Be able to recognize diagrams of single, double, and triple covalent bonds.
    Single bonds have one line, double bonds have two lines, and triple bonds have three lines between atoms.

22. How do you classify compounds based upon their E.N.D.? (what are the "threshold numbers"?)
    Compounds can be classified by their electronegativity difference (E.N.D.):

• Nonpolar covalent: 0 – 0.4

• Polar covalent: 0.4 – 1.7

• Ionic: 1.7 or greater.

1. How do you classify compounds by the type of elements involved?

• Ionic bonds: Between metals and nonmetals.

• Covalent bonds: Between nonmetals.

• Metallic bonds: Between metals.

1. Describe how metallic bonds are possible even though metals always form positive ions?
   In metallic bonds, delocalized electrons move freely between metal cations, creating a "sea of electrons" that hold the metal ions together.

2. What does delocalized electrons mean? What was the metaphor given to describe the delocalized electrons moving around the Aluminum cations?
   Delocalized electrons are electrons that are not bound to any one atom but move freely throughout the metal. The metaphor often used is that of "a sea of electrons" moving around positively charged metal ions.

3. What does aqueous mean? Solubility? Conductivity?
   Aqueous means something is dissolved in water. Solubility refers to the ability of a substance to dissolve in a solvent, and conductivity refers to the ability of a substance to conduct electricity, typically in liquid form or when dissolved in water.

4. What does binary mean? What do all binary compounds end in?
   Binary refers to compounds made of two elements. Binary compounds usually end in -ide (e.g., sodium chloride).

5. Chemical Formulas: What do the subscripts mean?
   Subscripts in a chemical formula indicate the number of atoms of each element in the compound.

• Example: In H₂O, the subscript 2 indicates there are two hydrogen atoms for each oxygen atom.

b. Be able to accurately count the atoms in a compound. Examples:

• Example: In CO₂, there is 1 carbon atom and 2 oxygen atoms.

29. Write chemical formulas for the following:

i. CuCl₂
Copper(II) chloride: Copper has a +2 charge, and chlorine has a -1 charge. Two chlorine ions balance the charge of one copper ion, so the formula is CuCl₂.

ii. (NH₄)₃PO₄
Ammonium phosphate: Ammonium (NH₄⁺) has a +1 charge, and phosphate (PO₄³⁻) has a -3 charge. To balance, you need 3 ammonium ions for every phosphate ion, giving the formula (NH₄)₃PO₄.

iii. Al(C₂H₃O₂)₃
Aluminum acetate: Aluminum (Al³⁺) has a +3 charge, and acetate (C₂H₃O₂⁻) has a -1 charge. You need 3 acetate ions to balance the charge of one aluminum ion, so the formula is Al(C₂H₃O₂)₃.

30. Name covalent compounds:

a. Three steps for naming covalent compounds:

1. Name the first element in the compound, using its full name.

2. Name the second element by modifying the name to end in -ide.

3. Use prefixes to indicate the number of atoms of each element.

b. Prefixes and their meanings:

• Mono- = 1

• Di- = 2

• Tri- = 3

• Tetra- = 4

• Penta- = 5

• Hexa- = 6

• Hepta- = 7

• Octa- = 8

• Nona- = 9

• Deca- = 10

c. What do the compounds have as an ending? Covalent compounds end in -ide (e.g., carbon monoxide, CO).

d. What will you NOT find in these compounds?

• You will not find ions or oxidation states in covalent compounds.

31. Write chemical formulas for covalent compounds:

a. Know the prefixes for 1 to 10: See the list above for prefixes.

b. Do your criss-cross or simplify subscripts? For covalent compounds, you do not criss-cross charges (this is for ionic compounds). Use the prefixes to determine the correct subscripts.

32. Name ionic compounds:

a. What are two ways you know for sure you have an ionic compound?

• It is made of a metal and a nonmetal.

• It contains charges, either in the form of ions or a polyatomic ion.

b. What types of elements are involved in ionic compounds?
Ionic compounds involve metals and nonmetals (or polyatomic ions).

c. What clue tells you that a polyatomic ion is in an ionic compound?
Polyatomic ions are often written in parentheses in the formula and are usually accompanied by a charge (e.g., NH₄⁺, SO₄²⁻).

d. What is an oxidation number? How is it written on the ion?
An oxidation number is the charge of an ion, and it is written as a superscript (e.g., Na⁺ has an oxidation number of +1, O²⁻ has an oxidation number of -2).

e. What is a tertiary ionic compound?
A tertiary ionic compound contains three different elements (i.e., a metal, a nonmetal, and a polyatomic ion).

f. What is the name for the common POSITIVE polyatomic ion?
The common positive polyatomic ion is ammonium (NH₄⁺).

g. What do most of the polyatomic ions end in?
Most polyatomic ions end in -ate or -ite (e.g., nitrate NO₃⁻, sulfate SO₄²⁻).

h. When using polyatomic ions, Mrs. M says to always put them in ______ with the charge on the top right OUTSIDE of the __________.
You put polyatomic ions in parentheses with the charge on the top right outside of the parentheses.

i. What do you need if your compound has a transition metal?
You need to include the oxidation state of the transition metal, often indicated by a Roman numeral (e.g., Fe²⁺ in iron(II) chloride, FeCl₂).

33. Write chemical formulas for ionic compounds:

a. Which ion is always written first (on the left) in a compound?
The positive ion (cation) is always written first.

b. What are the common oxidation states for the elements in groups: 1, 2, 13, 14, 15, 16, and 17?

• Group 1: +1 (e.g., Na⁺)

• Group 2: +2 (e.g., Mg²⁺)

• Group 13: +3 (e.g., Al³⁺)

• Group 14: +4 (e.g., Sn⁴⁺)

• Group 15: -3 (e.g., N³⁻)

• Group 16: -2 (e.g., O²⁻)

• Group 17: -1 (e.g., Cl⁻)

c. What does the Roman Numeral in a name mean (if there is one)?
The Roman numeral indicates the oxidation state of a transition metal in the compound.

d. What does “criss-cross” mean (if you are using the algebraic way to form compounds…don’t worry about this one)?
The “criss-cross” method involves swapping the oxidation numbers between the ions to form the correct subscripts.

e. What does simplify the subscripts mean?
After criss-crossing, you should simplify the subscripts to the lowest whole numbers.

34. Write and name hydrate compounds:

Hydrates are compounds that include water molecules in their structure. To name hydrates:

1. Name the ionic compound.

2. Add a prefix for the number of water molecules.

3. Add "hydrate" at the end.

For example:

• CuSO₄·5H₂O is Copper(II) sulfate pentahydrate.

• MgCl₂·6H₂O is Magnesium chloride hexahydrate.

Prefixes for naming water molecules:

• 1 = mono-

• 2 = di-

• 3 = tri-

• 4 = tetra-

• 5 = penta-

• 6 = hexa-

• 7 = hepta-

• 8 = octa-

• 9 = nona-

• 10 = deca-