Lesson PDF: Review of Ionic and Covalent Bonding PDF

Review Ionic and Covalent Bonding 1. Electron transfer in ionic bonding. 2. Represent ionic compounds as dot-and-cross diagrams. 3. Understand properties of ionic compounds. 4. Electrons shared in covalent bonds. 5. Represent molecules as dot-and-cro...

Review Ionic and Covalent Bonding 1. Electron transfer in ionic bonding. 2. Represent ionic compounds as dot-and-cross diagrams. 3. Understand properties of ionic compounds. 4. Electrons shared in covalent bonds. 5. Represent molecules as dot-and-cross diagrams. 6. Understand properties of simple molecular structures, diamond, and graphite. Textbook: Read pages (ionic) 75 to 83, (covalent) 85 to 96. Ionic bonding Groups 1, 2, and 3 lose electrons to have a full outer shell. Groups 5, 6, and 7 gain electrons to have a full outer shell. Group Charge 1 1+ 2 2+ 3 3+ 5 3- 6 2- 7 1- Polyatomic CO32- HCO3- NO3- ions SO42- OH- NH4+ Ionic bonding What is an ion? An atom or molecule with a net electric charge due to the loss or gain of one or more electrons. Ionic bonding Explain how an ionic bond is formed between sodium and chlorine. Sodium gives away its 1 outer electron to chlorine. Sodium becomes a cation and chlorine becomes an anion. Now they both have full outer shells. The positive and negative charges are attracted to each other to form the ionic compound sodium chloride. Task 1: Go to page 83 in your textbook. Answer question 1. Task 1: Ionic bonding Formula of ionic compounds Once you know the formula of the ions involved, you can work out the formula of the compound formed. Mg = group 2 = 2+ Cl = group 7 = - Al = group 3 = 3+ O = group 6 = 2- Task 2: Go to page 84 in your textbook. Answer questions 3 and 4. Task 2: Ionic bonding Dot-and-cross diagrams help us see what happens to the electrons of an atom when they form a compound. Step 1: Draw the original atoms. Step 2: Add arrow(s) to show how the electrons are transferred. Step 3: Draw the ions formed. Ionic bonding Step 3: Draw the ions formed. 1. Draw the ion with the full outer shell. 2. Add square brackets. 3. Add the charge in the top right corner. Ionic bonding Task: Draw the dot-cross diagrams of magnesium and oxygen to show the transfer of electrons. Include the dot-and-cross diagram of the magnesium and oxygen ions formed. Task 3: Go to page 83 in your textbook. Answer question 2. Task 3: Answers Ionic bonding Electrostatic Attraction: strong force of attraction between 2 oppositely charged ions Ionic bonding GIANT IONIC LATTICE Oppositely charged ions arrange themselves into a repeating pattern of alternating charges by electrostatic attraction forces. This makes sure that each ion is surrounded by ions of opposite charge. Ions form a “lattice” structure. Ionic bonding Go to page 82 and 83 in your textbook. Determine the following properties of ionic compounds. Melting/boiling point: Solubility: High melting and boiling point. Ionic substances tend to be soluble in Strong electrostatic forces of attraction water, but insoluble in organic solvents hold the lattice together. A lot of energy (like ethanol or acetone). is required to break the forces between oppositely charged ions. Electrical conductivity: Do not conduct as solids, the ions are Shape: fixed in place. Do conduct when molten Ionic compounds are crystalline. Even (liquid) or dissolved in water as ions ionic compounds like MgO that look like are free to move. powder are crystals under microscopes. Note: You will lose points on a test if you write that the electrons of an ionic Strength: compound move. Ionic crystals are brittle. Click box to reveal answer. Ionic bonding Ionic compounds have very HIGH melting and boiling points. This means that to change state of matter, high temperatures are required. High temperature = High amount of thermal energy Lots of energy is needed to overcome/break the strong electrostatic forces of attraction between the ions. Particles have more kinetic energy Particles move faster Ions overcome electrostatic attraction, separate Ionic bonding Ionic compounds DO NOT conduct electricity in solid state. Ionic bonds have strong electrostatic forces of attraction. Ions are unable to move. They DO conduct electricity in molten and dissolved state. Ions are charged particles. When the ions are free to move, they can carry electrical current. Note the ions are moving when ionic compounds are molten or dissolved, not electrons. Task 4: Go to page 84 in your textbook. Answer question 5. Task 4: Covalent Bonding Covalent bonding A covalent bond forms when atoms share electrons to complete their octet. This usually involves only non-metal elements. A substance containing covalent bonds is called a molecule. Covalent bonds also occur when non-metal atoms share electrons. H2O, CH4, CO2, NH3, HCl, O2, and many more! Task 5: Go to page 96 in your textbook. Answer question 1. Task 5: Covalent bonding Atoms share electrons equally in a covalent bond. Fluorine (group 7) has 7 outer electrons and needs to gain 1 more to have a full outer shell. The pairs of electrons In total, each atom has that are not shared 8 electrons, following are called lone pairs. the octet rule. A covalent bond can also be drawn as a line. A pair of shared electrons is known as a single covalent bond. Chemical formula: F2 Covalent bonding Oxygen (group 6) makes 2 single bonds or one double bond. Oxygen can make two single bonds Oxygen forms a double bond with with 2 hydrogen atoms. another oxygen atom. Chemical formula: H2O Chemical formula: O2 Covalent bonding Nitrogen (group 5) makes 3 single bonds or one triple bond. Nitrogen can make three single Nitrogen forms a triple bond with bonds with 3 hydrogen atoms. another nitrogen atom. Chemical formula: NH3 Chemical formula: N2 Covalent bonding Single covalent bond = 1 bond = 2 shared electrons = 1 pair Double covalent bond = 2 bonds = 4 shared electrons = 2 pairs Triple covalent bond = 3 bonds = 6 shared electrons = 3 pairs Covalent bonding Carbon (group 4) makes 4 bonds. Describe the bonding of each molecule below. Carbon dioxide contains Methane contains 2 double bonds. 4 single bonds. Chemical formula: CH4 Chemical formula: CO2 Covalent bonding What holds atoms with a covalent bond together? The nuclei of the atoms in the molecule are both attracted to the shared electrons. Task 6: Go to page 96 in your textbook. Answer questions 2 and 3. Task 6: S Si P Task 6: Answers *Question does say outer electrons only, drawing all electrons is also correct. Covalent bonding Molecules with only a few atoms are called simple molecular structures. The covalent bonds that hold the atoms together are very strong! However, molecules are only held to each other by weak intermolecular forces. The intermolecular forces between molecules are much weaker than covalent bonds. When we boil water, it is only these weak intermolecular forces of attraction that are broken, covalent bonds are not broken. Covalent bonding Relative Melting Point Boiling Point Halogen Formula (°C) (°C) Mass Fluorine (F2) 38 -220 -188 Chlorine (Cl2) 71 -101 -34 Bromine (Br2) 160 -7 59 Iodine (I2) 254 114 184 Molecules with higher formula mass have higher melting and boiling points. More energy is needed to break the intermolecular forces. Covalent bonding Giant Covalent Structures: Giant covalent structures have very large structures of atoms that go on and on with no fixed number of atoms. Diamond Graphite Covalent bonding Each carbon in diamond makes 4 bonds.\ Carbon makes a 3D tetrahedral shape which is extremely strong. This is why diamond is one of the hardest substances known to man. Diamond has a very high melting point (almost 4000°C). This is because, unlike simple molecular structures, when giant covalent structures melt, the covalent bond breaks. This requires a lot of energy. Covalent bonding In graphite, each carbon only makes 3 bonds. The carbon atoms arrange themselves in 2D sheets which can slide above and below each other. This is why graphite is softer than diamond and easily broken. The unbonded electron can leave the atom, becoming a delocalised electron which is able to move through the layers of graphite. The delocalised electrons allows graphite to conduct electricity. Graphite is a giant covalent structure so it also has a very high melting point. Covalent bonding C60 Fullerene is a simple molecular structure because of its fixed number of atoms and low melting/boiling point. Only the weak intermolecular forces of attraction between molecules hold Fullerene together. Covalent bonding How to tell simple molecular structures from giant covalent structures. Simple molecular structures are held Giant structures have no intermolecular together by weak intermolecular forces. A forces are held together by strong small amount of energy is needed to covalent bonds. A large amount of energy break them, so they have a low melting is needed to break them, so they have a and boiling point. high melting and boiling point. Task 7: Go to page 96 in your textbook. Answer questions 4 and 5. Task 7: Covalent bonding How to tell simple molecular structures from giant covalent structures. Substance Conductive MP (°C) BP (°C) allotrope substances hydrogen (H2) No -259 -252 Covalent Simple water (H2O) No 0 100 molecular ammonia (NH3) No −77 −33 structure diamond No 4000 4800 Giant Carbon covalent graphite Yes 3650 4200 structure C60 Fullerene No 280 526 Simple molecular structure Covalent bonding Go to page 92 and 93 in your textbook. Determine the following properties of simple molecular structures. Definition of molecule: Name of the force of attraction between Molecules contain a fixed number of molecules: atoms joined by covalent bonds. Intermolecular forces (ex: H2O, O2, C6H12O6, etc.) Electrical conductivity: Melting/boiling point: Covalent molecular compounds do not Low melting and boiling point. Not much conduct electricity. They do not have ions energy is needed to break and all their electrons are tightly held in intermolecular forces. (No covalent the atom or covalent bond. bonds are broken.) Boiling point increases with higher molecular mass. Solubility: Most covalent substances are insoluble Strength: in water but soluble in organic solvents. Weak Click box to reveal answer. Covalent bonding Go to page 93 and 94 in your textbook. Determine the following properties of diamonds. Atoms in diamond: Melting/ Boiling Point: Carbon Very high, a high amount of energy is needed to break the strong covalent Number of bonds (each carbon): bonds between carbon atoms. Four Shape: Electrical conductivity: 3D, Tetrahedral Does not conduct electricity. All of the atoms in carbon’s outer shell are held in covalent bonds. Click box to reveal answer. Covalent bonding Go to page 94 and 95 in your textbook. Determine the following properties of graphite. Atoms in graphite: Melting/ Boiling Point: Carbon Very high, a high amount of energy is needed to break the strong covalent Number of bonds (each carbon): bonds between carbon atoms. Three Shape: Electrical conductivity: 2D, layers Graphite does conduct electricity. Each carbon atom bonds with only 3 others, leaving its fourth outer electron free to move through the layers of graphite. The free electrons are called delocalised electrons. Click box to reveal answer. Task 8: Go to page 96 in your textbook. Answer question 6. Task 8: Answers