Lesson 16: Ionic Bonding

Transcription

1 NOTES Name: Date: Class: Lesson 16: Ionic Bonding Box 1: Directions: Match the term with the correct definition / description. 1. anion a. subatomic particle with no charge 2. cation b. present in the outermost shell; has most energy 3. electron c. calculated by subtracting total electrons valence electrons 4. neutron d. subatomic particle with +1 charge and a mass of 1 amu 5. proton e. subatomic particle with -1 charge and a mass of 0 amu 6. electron cloud f. an ion that has more electrons than protons 7. valence electron g. the region of negative charge surrounding an atomic nucleus 8. core electron h. an atom that has lost electrons A Bohr model of a Lithium atom is drawn to the left. A neutral atom of Li has protons and electrons. Li has electron shells and valence electron(s). As Li forms an ion, it will electron(s) and become a(n). A Bohr model of a Chlorine atom is drawn to the right. A neutral atom of Cl has protons and electrons. Cl has electron shells and valence electron(s). As Chlorine forms an ion, it will electron(s) and become a(n) 1

2 Electrons do not just disappear and re-appear. Electrons can be from atoms to atoms, which results in formation of and bonds. Remember the trend of ion formation: lose electrons and gain electrons. If a metal and nonmetal react, the will donate electrons to to form an chemical bond. Atoms gain or lose electrons so they become stable with a - just like the! Number of p+ Number of e- Net charge Neutral Lithium Atom Neutral Chlorine Atom Number of p+ Number of e- Net charge Lithium cation Chlorine anion 2

3 IMPORTANT FACTS: An ionic bond is the result of being. Ionic bonds only occur between (including ions that contain more than one atom called ). Ionic bonds involve between within a. Ionic bonds are also called. Ions have full and are just like the. Crystal lattice structure of salts: Ionic compounds (salts) are neutral, which means the positive charges and negative charges must be. For example, we know from looking at the that Lithium will form an ion with a charge of and Chlorine will form an ion with a charge of. In order for the charges to be balanced in a stable, neutral compound, Li + cation needs to be bonded to Cl - anion. 3

4 Practice: Ions DIRECTIONS: Write the ion that each neutral atom will form. Then, answer questions A and B. 1. Ca Ca Ba 5. Rb 2. Na 4. Se 6. Br A. Of the above atoms, which will gain electrons? B. Which will lose electrons? Writing Chemical Formulas for Ionic Compounds: All compounds have a chemical formula which shows the and of atoms in it. are always written first. Subscripts (small numbers written to the bottom right of each element symbol) tell you the (proportion) of the elements present in a compound but not or arrangement of atoms. The subscripts are the smallest whole ratio of ions in the salt - this is called the. No subscript? Assume it s Li3N There are no charges in the chemical formula because all the charges added up is ZERO for ionic compounds. MgCl2 Three Li + ions One N 3- ion One Mg 2+ ion Two Cl - ions VOCABULARY ALERT!!!! We refer to salts as compounds or formula units. Ionic compounds are the result of giving/gaining electrons and are not molecules. Molecules only refer to compounds where electrons are shared in covalent bonds (next lesson). Practice: 1. Write the empirical formula of a compound that consists of one scandium (Sc) ion per every three chloride (Cl) ions. 2. Write the empirical formula of a compound that consists of three sodium (Na) ions per every phosphide (P) ion. 3. Write the empirical formula of a salt crystal that contains 2,000,000 cesium (Cs) ions and 1,000,000 sulfide (S) ions. 4

5 Box 2: Match the term with the correct definition / description. The definitions may be used more than once. 1. sublimation A. solid liquid 2. boiling B. liquid solid 3. melting C. gas solid 4. deposition D. solid gas 5. condensation E. liquid gas 6. vaporization F. gas liquid 7. evaporation 8. freezing Diagraming Ionic Bonds with Bohr Models: Diagram how an ionic compound forms between two elements. Make sure your drawing is easy to understand and includes the following: a. each atom has correct electron shells b. each atom has correct valence electrons c. arrows drawn to show movement of electrons and the resulting bond d. chemical formula for neutral compound 1. One sodium atom (Na) and one Chlorine atom (Cl). 2. One beryllium atom (Be) and two fluorine atoms (F). 5

6 Determining Empirical Formulas: **In neutral compounds, the positive charges and negative charges must be balanced to sum up to zero.** How many Bromide (Br) ions would it take to balance the charge of one Potassium ion (K + )? Write the chemical formula of the compound formed between K and Br. **Cations are written first** How many Chloride (Cl) ions would it take to balance the charge of one Gallium ion? Write the chemical formula of the compound formed between Ga and Cl. How many Magnesium (Mg) ions would it take to balance the charge of two Fluoride ions (F - )? Write the chemical formula of the compound formed between Mg and F. How many Zinc ions would it take to balance the charge of one nitride ion? Write the chemical formula of the compound formed between Zn and N. 6

7 How to write chemical formulas for ionic compounds: Step 1: Write the that the metal will form followed by the ion that the nonmetal will form. Step 2: Determine how to by finding the of the charges on each ion. Step 3:. Chemists talk about the of the ions in ionic compounds. PRACTICE: Write the chemical formulas for compounds formed between the following elements: EXAMPLE: Magnesium + Bromine Ions formed: Chemical formula: 1. Sodium + Selenium Ions formed: Chemical formula: 2. Silver + Nitrogen Ions formed: Chemical formula: 3. Aluminum + Oxygen Ions formed: Chemical formula: 4. Potassium + Sulfur Ions formed: Chemical formula: 7

8 5. Strontium + Nitrogen Ions formed: Chemical formula: 6. Barium + Sulfur Ions formed: Chemical formula: 7. Gallium + Oxygen Ions formed: Chemical formula: 8. Cadmium + Selenium Ions formed: Chemical formula: There are three types of chemical bonds: Binary I Binary II Binary III Types of atoms involved Ionic bonds between two ions (metal + nonmetal) Metals involved: Alkali metals, Alkaline earth metals, Ag +, Cd 2+, Zn 2+, Al 3+, Ga 3+ In 3+ Ionic bonds between two ions (metal + nonmetal) Metals involved: All other metals (transition metals and post-transition metals) Covalent bond between two nonmetals (electrons shared between nonmetals or nonmetal + metalloid) Naming scheme: name of metal + name of nonmetal with ide ending name of metal + Roman numeral with charge of cation + name of nonmetal with ide ending PREFIX*name of first element + PREFIXname of second element with ide ending Prefixes tell you how many of each atom is present. *Don t use mono if there is one atom of the first element Other notes Empirical formula (lowest whole number ratio of ions in compound only) Empirical formula (lowest whole number ratio of ions in compound only) Molecular formula (actual numbers of each atom per molecule) 8

9 Determining Charges of Ions: +3 We ve been doing Binary I thus far. Binary I compounds involve metals from Group 1A, Group 2A, and Ag, Zn, Cd, Al, Ga, In) Binary I metals only have charge possible and you can figure out their charge by their position on the Periodic Table Group 1A metals will always form anions. Group 2A metals will always form anions. The triangle metals form variable ions. Binary II metals form types of cations. For example, Iron can form Fe 2+ or Fe 3+ ions. Binary II metals include all the other metals that are not Binary I. You will need to to determine the charge of the cation in each compound by finding the lowest common multiple and having the positive and negative charges add up to zero. Practice: Balance the charges. For each salt, what is the charge of the cation? 1. Au 2S 2. AuS 3. Hg 3N 2 4. MnCl 6 9

10 Naming Ions Naming monoatomic cations (metals) = identified simply by the. Examples of cations: Element Name of its cation Potassium Lithium Silver Naming monoatomic anions (nonmetals) = (1) drop the ending of the element s name + (2). Examples of anions: Element Name of its anion Fluorine Nitrogen Oxygen Practice: Name the ions Na + = Cl - = Br - = I - = Al 3+ = S 2- = Box 3: Physical / chemical changes or properties? 1. A piece of iron rusting = 2. Water evaporating = 3. Melted wax cooling into solid wax = 4. A candle wick burning = 5. At room temperature, liquid nitrogen boils = 6. Benzene-carbonic-acid is a monobasic aromatic acid, moderately strong, white crystalline powder, very soluble in alcohol, ether, and benzene, but poorly soluble in water. = 7. Sodium is a soft metal that is reactive with air = 10

11 Box 4: Label the arrows to name each phase change. VOCABULARY ALERT!!!!! mono means one and poly means many. Naming Compounds name of metal* + name of nonmetal plus ide ending *1A metals, 2A metals, Ag, Zn, Cd, Al, In, Ga PRACTICE: For each pair of elements forming an ionic bond, write its chemical formula and name. Use the empty space to show work for balancing charges. Empirical formula: Name: 1. Zinc + Sulfur 2. Calcium + Bromine 3. Silver + Phosphorus 4. Potassium + Selenium 5. Rubidium + Nitrogen 6. Aluminum + Oxygen 7. Sodium + Hydrogen 11

12 name of metal* + Roman numeral to show the charge of the cation + name of nonmetal plus ide ending The charge of most transition metals cannot be determined simply by looking at the Periodic table. You must balance charges because all ionic compounds are electrically neutral. The Roman numeral is only in the name, never in the formula. Examples: *all other metals that are not Binary I 1. Manganese (II) sulfide 2. Iron (III) chloride Formula: Formula: 3. If an ionic bond is formed between three iron (Fe) atoms and two nitrogen (N) atoms a) What is the charge of the Fe ion? b) What is the chemical formula? c) What is the name? 4. If an ionic bond is formed between one manganese (Mn) atom and two selenium (Se) atoms a) What is the charge of the Mn ion? b) What is the chemical formula? c) What is the name? 12

13 PRACTICE: Given the empirical formulas for each compound, write the name. Use the extra space to balance charges and determine the charge on the cation. 1. CrP 2. Fe 2O 3 3. SnF 4 4. Cu 2S 5. PbF 2 6. PbS 2 7. Cu 3N Roman numerals: I II III IV V VI VII VIII IX X PRACTICE: Given the name of each compound, write the empirical formula. Use the extra space to balance charges. 1. nickel (II) sulfide 2. scandium (II) chloride 3. gold (I) oxide 4. gold (II) oxide 5. lead (IV) sulfide 6. iridium (III) iodide 7. chromium (VI) nitride 13

14 Monoatomic Ions vs. Polyatomic Ions Monoatomic ions = Polyatomic ions = Polyatomic ions are groups of covalently bonded atoms that have lost or gained electrons. They function as one unit and do not separate during ionic bonding. List of Polyatomic Ions you will need to memorize: + 2- Ammonium NH 4 Carbonate CO 3 Hydroxide OH - Sulfate SO Nitrate NO 3 Phosphate PO 4 **You ll need to memorize the formulas and charges of these so you can apply them to ionic bonding.** Update in Naming Rules: If a compound has a polyatomic ion, use the name of the polyatomic ion (no changes). Other notes: When writing chemical formulas, only if there are multiple polyatomic ions per formula unit, Polyatomic anions can bond with metal cations. PRACTICE: Write the name of each compound. Watch out for Binary I vs. Binary II. 1. Li 2SO 4 2. (NH 4) 2S 3. NaOH 4. Rb 3PO 4 5. Ni(OH) 2 6. Cr(NO 3) 3 7. MgCO 3 8. Mn(PO 4)

15 Counting Atoms Na2SO4 (NH4)2S LiOH Cs3PO4 Element # of atoms Element # of atoms Element # of atoms Element # of atoms Total Total Total Total Co(OH)2 Fe(NO3)3 CaCO3 Cr(PO4)3 Element # of atoms Element # of atoms Element # of atoms Element # of atoms Total Total Total Total Box 5: Imagine you re shooting arrows at the bull s eye boards below. Draw X marks to represent arrows and match your aim to the descriptions below each board. 2. What is the difference between precise measurements and accurate measurements? 15

16 Box 6: Pass around the five demo cubes (white plastic, clear acrylic, wooden, copper, and aluminum). 1. Which cube contains the most matter? 2. Identify which cube is more dense: a. wooden cube vs. copper cube b. clear acrylic cube vs. aluminum cube c. copper cube vs. aluminum cube 3. Aluminum has a density of 2.7 g/cm 3. Make your best guess for the density of copper. a. 1.4 g/cm 3 c. 8.8 g/cm 3 b. 3.1 g/cm 3 d g/cm 3 4. The mass of the clear acrylic block is 16.8 g. The density of acrylic is 1.2 g/cm 3. What is the volume of the cube? Box 7: Vocabulary solute, solvent, solution, mixtures g of sucrose was added into 500 ml of water and mixed thoroughly to make a homogeneous mixture. a. The sucrose is the. b. The water is the. c. The resulting mixture is called a(n). d. What do you expect this mixture to look like? ml of water was added to 980 ml of ethanol and mixed thoroughly. a. The ethanol is the. b. The water is the. 3. Humid air can have up to 4% water vapor. a. The water vapor is the. b. The air is the. 4. The gets dissolved into the. There is always more of the. 16

17 From the Lewis Diagrams below, write the chemical formula and name of each polyatomic ion. The lines between the atoms represent covalent bonds (sharing of pairs of electrons between each atom). Name: Chemical formula: Name: Chemical formula: Name: Chemical formula: Name: Chemical formula: Name: Chemical formula: Name: Chemical formula: 17

18 Given the chemical formula, write the name of each ionic compound. Remember your rules for Binary I vs. Binary II. Use extra space at the bottom to balance charges if needed. Binary I or II? Name: 1. Li 2SO 4 I II 2. Cd(NO 3) 2 I II 3. Co(OH) 3 I II 4. FeBr 3 I II 5. Cr(NO 3) 6 I II 6. TiS 2 I II 7. YPO 4 I II 8. AgNO 3 I II 9. (NH 4) 3SO 4 I II 10. Al 2(CO 3) 3 I II 11. Pd 3P 2 I II 12. MnPO 4 I II When do you need to use parentheses? When do you need to use Roman numerals? 18

19 Given the name, write the chemical formula. Remember your rules for Binary I vs. Binary II. 1. manganese (VII) oxide 2. iron (II) iodide 3. vanadium (V) nitrate 4. strontium sulfate 5. calcium carbonate 6. copper (I) phosphate 7. ammonium sulfide 8. nickel (II) hydroxide Circle the compounds below that contain ionic bonds. Na 2SO 4 CO 2 LiCl CuCO 3 H 2O 2 Sr(OH) 2 RbF BF 3 CH 4 SO 2 Properties of Ionic Compounds Ionic compounds have and points. o o o Melting = substance changes phase from a to a Boiling = substance changes phase from a to a Why? (a lot of ) is required to overcome the between cations and anions. o Example: Table salt (NaCl) has a melting point of (1,474 F)! Zinc chloride (ZnCl 2) has a melting point of 275 C (527 F) and a boiling point of 756 C! Ionic compounds have a. o Cations and anions to form a three-dimensional structure. 19

20 Ionic compounds are. o Why? The positive cations and negative anions are and. o Define brittle = Ionic compounds when (in ). o In water, the ions (move apart) and freely move through the solution. o ionic compounds ( ) also conduct electricity. o Ionic compounds are. 20

21 PRACTICE: Circle the properties that are characteristic of substances containing ionic bonds. 1. low melting point 2. high melting point 3. low boiling point 4. high boiling point 5. strong bond strength 6. weak bond strength 7. sublimes at room temperature 8. liquid at room temperature 9. crystalline solid at room temperature 10. electrolyte 11. does not conduct electricity at all 12. conducts electricity when a solid 13. conducts electricity when melted 14. conducts electricity in aqueous solutions 15. soft 16. hard 17. malleable 18. brittle 19. composed of a metal and nonmetal 20. composed of two nonmetals Box 8: 1. In the formula XSO 4, the symbol X could represent the element a. Al c. Mg b. Ar d. Na 2. A substance changes directly from a solid to a gas during a. deposition c. sublimation b. saponification d. vaporization 3. What is the chemical formula for copper (II) hydroxide? a. CuOH c. CuOH 2 b. Cu 2(OH) d. Cu(OH) 2 4. In the ground state, all of the atoms of Period 3 elements have the same a. atomic mass c. number of occupied energy shells b. atomic number d. number of oxidation states 5. Element X reacts with chlorine to form an ionic compound that has the formula XCl 2. To which group on the Periodic table could element X belong? a. Group 1 c. Group 2 b. Group 13/3A d. Group 15/5A 21

22 Box 9: Diagram how an ionic compound forms between atoms of Beryllium and Fluorine. Make sure your drawing is easy to understand and includes the following: a. each atom has correct electron shells b. each atom has correct valence electrons c. arrows drawn to show movement of electrons and the resulting bond d. chemical formula for neutral compound Box 10 Box