| A | B |
|---|
| What does a full outer energy level consist of? | two valence electrons for helium and eight valence electrons for all the other noble gases |
| What does the octet rule state? | atoms lose, gain, or share electrons to achieve a stable configuration of 8 valence electrons or an octet |
| What is a covalent bond? | the chemical bond that results from the sharing of valence electrons |
| When does covalent bonding generally occur? | when elements are relatively close to each other on the periodic table and it usually forms between nonmetallic elements |
| What forms when two or more atoms bond covalently? | a molecule |
| Why does flourine exitst as a diatomic molecule? | Each flourine atom has seven valence electrons and must have one additional electron to form an octet. The sharing of one pair of electrons will give both flourine atoms stable noble gas configurations |
| These diagrams use electron-dot diagrams to show how electrons are arranged in molecules. The shared electron pair, often referred to as the bonding pair, is represented by either a pair of dots or a line in the Lewis structure for the molecule. | Lewis Structure |
| What Greek letter represents single covalent bonds? | sigma represents sigma bonds |
| What Greek letter denotes a bond where parallel orbits overlap to share electrons? | pi which stands for pi bonds |
| What does the strength of a covalent bond depend on? | how much distance separates bonded nuclei. |
| What is bond length? | bond length is the distance from the center of one nucleus to the center of the other nucleus of two bonded atoms. |
| How does the number of shared electrons shared relate to the bond length? | As the number of shared electron pairs increases, bond length decreases. The shorter the bond length, the stronger the bond. |
| What do we call the amount of energy needed to break a specific covalent bond? | bond dissociation energy |
| These reactions occur when a greater amount of energy is required to break the existing bonds in the reactants than is released when the new bonds form in the product molecules. | Endothermic reactions |
| These reactions occur when more energy is released forming new bonds than is required to break bonds in the initial reactions. | Exothermic reactions |
| Name the following binary covalent compound: CCL4 | carbon tetrachloride |
| name the following binary covalent compound: As2O3 | diarsenic trioxide |
| Name the following binary covalent compound: CO | carbon monoxide |
| Name the following binary covalent compound: SO2 | sulfur dioxide |
| Name the following binary covalent compound: NF3 | nitrogen triflouride |
| When is a compound considered an acid? | If they produce H+ or hydrogen ions in a solution |
| What do we call a binary acid that contains hydrogen and one other element? | binary acid |
| What do we call any acid that contains hydrogen and an oxyanion? | oxyacid |
| Name the following acid (dissolve in water) HI | hydroiodic acid |
| Name the following acid (dissolved in water) HCIO3 | chloric acid |
| Name the following acid (dissolved in water) HCIO2 | chlorous acid |
| Name the following acid (dissolved in water) H2SO4 | sulfuric acid |
| Name the following acid (dissolved in water) H2S | hydrosulfuric acid |
| What is one of the most useful molecular models that uses letter symbols and bonds to show relative position of atoms? | structural formulas like the Lewis structure |
| In the Lewis structure, this is always the terminal or end atom. It can only be connected to one other atom because it can share only one pair of electrons. | hydrogen |
| This is the atom with the least attraction for shared electrons in the molecule. This element is usually the one closer to the left on the periodic table. It is located in the center of the molecule and all other atoms become terminal atoms. | central atom |
| How do you find the total number of electrons available for bonding? | the number of valence electrons in the atoms in the molecule |
| How do you determine the number of bonding pairs? | You divide the number of electrons available for bonding by two |
| Where do you place the bonding pair (single bond)? | Place one bonding pair between the central atom and each of the terminal atoms. |
| What do you do with the remaining electron pairs that include lone pairs as well as pairs used in double and triple bonds? | Place them around each terminal atom bonded to the central atom to satisfy the octet rule. |
| Where are any remaining pairs assigned? | to the central atom |
| What do you do if the central atom is not surrounded by four electron pairs? | it does not have an octet. You must convert one or two of the lone pairs on the terminal atoms to a double bond or a triple bond between the terminal atom and the central atom. |
| Which elements can generally form double or triple bonds with the same element or with another element? | carbon, nitrogen, oxygen, and sulfur |
| Name the steps for drawing the Lewis structure for ammonia. You know that ammonia molecule consists of one nitrogen atom and three hydrogen atoms. Because hydrogen must be a terminal atom, nitrogen is the central atom. | First find the total number of valence electrons in both atoms: 5+3=8 atoms. Next, determine the number of bonding pairs by dividing the total number of electrons by 2 so 8 divided by two is 4 pairs. Next, draw 3 single bonds from each H to the N. Next, subtract the number of pairs used in these bonds from the total number of pairs of electrongs available so 4-3=1. Lastly, place the remaining lone pair on the central atom, N. |
| What are the steps to drawing the Lewis structure for carbon dioxide if you are given that the carbon dioxide molecule consists of one carbon atom and two oxygen atoms. Because carbon has less attraction for shared electrons, carbon is the central atom and the two oxygen atoms are terminal. | First, find the total number of valence electrons for both elements so 4+12=16. Second, determine the number of bonding pairs by dividing by 2 so 16 divided by two equals 8. Third, draw single bonds from each O to the central C. Fourth, subtract these two pairs from the 8 pairs available to get 6 lone pairs. Fifth, add these lone pairs to each terminal oxygen. Seventh, use a lone pair from each oxygen atom to form a double bond with the carbon atom. |
| What is the main difference in drawing the Lewis Structure for polyatomic ions and drawing the Lewis structure for covalent compounds? | The main difference is in finding the number of electons available for bonding. You subtract the ion charge if the ion is positive and you add the ion charge if the ion is negative. |
| List the steps for drawing the correct Lewis structure for the polyatomic ion phosphate. You are give that the phosphate ion consists of one phosphorous atom and four oxygen atoms and has a charge of -3. Phosphorous has less attraction for shared electrons so it is the central atom and the four oxygen atoms are the terminal atoms. | First, find the total number of valence electrons and add three electrons from the negative charge for a total of 32 valence electrons. Secondly, you determine the total number of bonding pairs by dividing 32 by 2 to get 16. Third, draw single bonds from each O to the central P. Third, you subtract the number of pairs used in these bonds from the total number of pairs available to get 12. Fourth, add these lone pairs to the terminal oxygen atoms. |
| A condition that occurs when more than one valid Lewis structure is written for a molecule or an ion. | Resonance |
| What happens when one atom donates a pair of electrons to be shared with an atom or ion that needs two electrons to become stable? | coordinate covalent bond |
| Draw the lewis structure for xenon tetrafluoride given that it consists of one xenon atom and four flourine atoms. Xenon has less attraction for electrons so it is the central atom. List the steps but know that this is an exception to the octet rule. | First, find the total number of valance electrons which is 36. Second, Determine the number of bonding pairs by dividing by two so you get 18. Third, Use four bonding pairs to bond the four F atoms to the central Xe atom. Fifth, determine the number of remaining pairs which is 14. Sixth, Add three pairs to each F atom to obtain an octet. Sixth, take the two remaining pairs and add them to the central Xe atom. |
| What is the VSEPR model? | The model used to determine the molecular shape of a molecule and is called the Valence Shell Electron Pair Repulsion model |
| What do we call the angle formed by any two terminal atoms and the central atom? | bond angle |
| Why are electrons in a molecule located as far apart as they can be from each other? | because it minimizes the repulsion of shared and unshared electrons around the central atom. |
| What do we call the process in which atomic orbitals are mixed to form new, identical hybrid orbitals? | hybridization |
| What does each hybrid orbital contain? | one electron that it can share with another atom |
| Why is the hybrid orbital for carbon called an sp3 orbital? | because the four hybrid orbitals form from one s and three p orbitals |
| How can we figure out the total number of atomic orbitals that mix to form the hybrid orbitals? | it equals the total number of pairs of electrons |
| Determine the molecular geometry, bond angle and type of hybridization for BF3? | trigonal planar, 120 degrees, sp2 |
| Determine the molecular geometry, bond angle and type of hybridization for NH4+? | tetrahedral, 109 degrees, sp3 |
| Determine the molecular geometry, bond angle and type of hybridization for OCI2? | bent, 104.5 degrees, sp3 |
| Determine the molecular geometry, bond angle and type of hybridization for BeF2? | linear, 180 degrees, sp |
| Determine the molecular geometry, bond angle and type of hybridization for CF4? | tetrahedral, 109 degrees, sp3 |
| What do we call the measure of the tendency of an atom to accept an electron? | electron affinity |
| Excluding noble gases, what happens to electron affinity as the atomic number increases within a given period? | it increases |
| Excluding noble gases, what happens to electron affinity as the atomic number increases within a group? | it decreases |
| What indicates the relative ability of an atom to attract electrons in a chemical bond? | electronegativity |
| How can we predict the character and type of chemical bond? | using the electronegativity difference of the elements that are bonded |
| When is a bond considered nonpolar covlanet or a pure covalent bond? | When the electrons in the bond are equally shared between the two atoms |
| What results because of unequal sharing in a covalent bond? | polar covalent bond |
| What do large differences in electronegativity (over 1.70) indicate? | ionic bonding |
| Why do polar covalent bonds form? | because not all atoms that share electrons attract them equally. The shared pair of atoms is pulled towards one of the atoms. |
| Why is a polar bond often referred to as a dipole? | The more electronegative atom is located at the partially negative end while the less electronegative atoms is found at the partially positive end. A polar molecule has a partial negative charge on one side while the other side has a partial positive charge. The molecule is a dipole because of the two partial charges. |
| How can you distinguish polar from nonpolar molecules? | Nonpolar molecules are not attracted by an electric field |
| Why are some molecules polar and some are not? | The symmetric molecules are usually nonpolar and the molecules that are asymmetric are usually polar |
| What do we call the ability of a substance to dissolve in another substance? | physical property solubility |
| Are polar molecules and ionic compouds usually soluble in pola substances? | Yes |
| What type of molecules only dissolve in nonpolar substances? | nonpolar |
| Why doesn't salt melt when you heat it up and sugar does? | many physical properties of covalent molecules are due to intermolecular forces. The melting and boiling points of molecular substances are relatively low compared to those of ionic substances. |
| Why do covalent molecules form relatively soft solids? | hardness is due to the intermolecular forces between individual molecules.. |
| What do we call the weak forces of attraction between individual molecules in a covalent compound? | van der waals forces |
| In covalent compounds, what pattern do the molecules form? | a crystal lattice |
| What do we call solids composed only of atoms connected by covalent bonds. They are typically brittle, nonconductors of heat or electricity, and extremely hard? | covalent network solids like diamonds |
| Is the molecule polar or nonpolar? SCI2 | polar |
| Is the molecule polar or nonpolar?H2S | polar |
| Is the molecule polar or nonpolar?CF4 | nonpolar |
| Is the molecule polar or nonpolar?CS2 | nonpolar |
