1. The outermost electrons in an atom are the electrons. 2. What is the scientific term for how likely something is to react? 3. How many valence electrons are in an oxygen atom? 4. The noble gases all have 8 valence electrons. Which of these describes the reactivity of the noble gases? A. Very high reactivity B. High reactivity C. Average reactivity D. Very low reactivity 5. An unknown atom has a very high reactivity. Which of these could describe the atom? A. The atom has 4 valence electrons. B. The atom has 7 valence electrons. C. The atom is a noble gas. D. The atom will not combine with other substances. Lesson 1.5 Molecules and Chemical Formulas Daily Question When chemists are working, what is the language they use and how do they stay organized? 1. A group of at least two atoms bonded together = molecule The atoms bonded together can be the same atom or different atoms. Different Atoms Identical Atoms I can describe molecules and how they are written using chemical symbols. (2a) 3. Each different atom in a molecule is shown with its chemical symbol from the periodic table. NaCl and HF are chemical formulas. 2. A way of showing the types and number of elements in a molecule = chemical formula Sodium Na Chlorine Cl I can describe molecules and how they are written using chemical symbols. (2a) 4. In a chemical formula, the number of atoms of each type in a single molecule is shown with subscripts (numbers shown after each element). a. If only one atom of that type is found in a molecule, the 1 is omitted (left out). The chemical formula for table salt is NaCl not Na 1 Cl 1. Oxygen O Oxygen O Carbon C CO 2 C1O2C1O2 I can describe molecules and how they are written using chemical symbols. (2a) How many atoms of sulfur are in H 2 SO 4 ? 1 I can describe molecules and how they are written using chemical symbols. (2a) How many atoms of oxygen are in Cr O 3 ? 3 I can describe molecules and how they are written using chemical symbols. (2a) Magnesium hydroxide or Mylanta is a medicine given to people with upset stomachs. It has a chemical formula of Mg(OH) 2. How many atoms of hydrogen are in each molecule of magnesium hydroxide? 2 I can describe molecules and how they are written using chemical symbols. (2a) 5. Sometimes a regularly sized number (the coefficient ) is shown in front of the molecule such as 2HNO 3. This means that there are a total of two molecules of HNO 3. HNO 3 = 2HNO 3 I can describe molecules and how they are written using chemical symbols. (2a) For example, caffeine has a chemical formula of C 8 H 12 N 4 O 3. If a scientist is describing three molecules of caffeine, it would be written at 3C 8 H 12 N 4 O 3. = 3C 8 H 12 N 4 O 3. I can describe molecules and how they are written using chemical symbols. (2a) 6. By multiplying the coefficient by the subscripts, we can determine the total number of each type of atom. a. In 4H 2 O 2, there are four different molecules with a total of hydrogen atoms and oxygen atoms. I can describe molecules and how they are written using chemical symbols. (2a) How many total atoms of iron are in 5Fe 2 O 3 ? 10 atoms of iron are in 5Fe 2 O 3. I can describe molecules and how they are written using chemical symbols. (2a) How many atoms of oxygen are in each molecule of magnesium hydroxide, 4Mg(OH) 2 ? 8 atoms of oxygen. Each molecule has two atoms of oxygen. I can describe molecules and how they are written using chemical symbols. (2a) Guided Practice List the different types of atoms in the molecule 1. CH Fe 2 O CaOH - 4. H 2 SO CH 3 Cl - List the total number of each type of atoms in the molecule 6. O 3 - atoms of oxygen 7. C 6 H 12 O 6 - carbon, hydrogen, 8. 4N 2 O - nitrogen, oxygen 9. 6CO H 3 PO 4 - I can describe reactants and products and how reactions are shown with equations. (2b) 1. A process that causes chemical substances to change into other substances = chemical reaction 2. The chemical substances that are started out with = reactants 3. The chemical substances formed by the reaction = products 2. A more simple explanation of a chemical reaction = chemical equation a. Chemical formulas of the reactants shown on the left b. Chemical formulas of the products shown on the right c. They are separated by an arrow ( ) HBr + NaOH NaBr + H 2 O I can describe reactants and products and how reactions are shown with equations. (2b) d. The tip of the arrow points in the direction in which the reaction occurs e. The state of each reactant and product is shown in subscripted parenthesis. i. (aq) means the substance is dissolved in water. ii. (s), (l), (g) the substance is in the solid, liquid, or gas state HBr (aq) + NaOH (s) NaBr (s) + H 2 O (l) (aq) = aqueous. If something is aqueous, it is dissolved in water. I can describe reactants and products and how reactions are shown with equations. (2b) 5. All of the types of atoms contained in the reactants must also appear in the products. a. The idea that matter cannot be created or destroyed = the Law of Conservation of Mass Zn (s) + 2HCl (aq) 2 H 2(g) + ZnCl 2(aq) I can describe reactants and products and how reactions are shown with equations. (2b) Do you know what that means? (5 questions) 1. Which of these describes when two or more of the same atom are bound together? A. Chemical formula B. Molecule C. Element D. Coefficient 2. Which of these is NOT a correctly written chemical formula? A. 12H 2 O B. NaCl C. H 2 S 1 O 4 D. 3 C 6 H 12 O 6 3. Which of these gives the correct number of atoms contained in a molecule of nitrous oxide N 2 O? A. A molecule of nitrous oxide contains 1 nitrogen atom and 2 oxygen atoms B. A molecule of nitrous oxide contains 2 nitrogen atoms and 1 oxygen atom C. A molecule of nitrous oxide contains 4 nitrogen atoms and 8 oxygen atoms D. A molecule of nitrous oxide contains 8 nitrogen atom and 4 oxygen atoms 4. How many atoms of oxygen are in a molecule with a chemical formula of 3 C 6 H 12 O 6 5. A scientist has discovered a new substance. It is made up one carbon atom, two chlorine atoms, and one oxygen atom. How would the scientist write a chemical formula for 6 molecules of the new substance?