Atoms, Molecules, and Ions Lesson Notes PDF

Lesson 2: ATOMS, MOLECULES, AND IONS Learning Competencies: At the end of the lesson, you are expected to… Describe common isotopes and their uses. Represent compounds using chemical formulas, structural formulas and models. Name compounds given their formula and write formula given the name...

Lesson 2: ATOMS, MOLECULES, AND IONS Learning Competencies: At the end of the lesson, you are expected to… Describe common isotopes and their uses. Represent compounds using chemical formulas, structural formulas and models. Name compounds given their formula and write formula given the name of the compound. The Atomic Structure The Atom An atom is a small, indivisible particle considered to be the basic unit of matter. An atom consists of three main subatomic particles, namely, protons, neutrons, and electrons.  COMPARISON OF THE DIFFERENT SUBATOMIC PARTICLES SUBATOMIC MASS SYMBOL CHARGE LOCATION PARTICLE (a.m.u.) + Inside the Proton p 1.0073 +1 nucleus 0 Inside the Neutron n 1.007 0 nucleus - Outside the Electron e 0.00055 -1 nucleus Representing an Atom Activity: Subatomic Particles Complete the table by providing the missing information. ATOMIC MASS NUMBER ELEMENTS NUMBER OF p+ NUMBER OF n0 NUMBER OF e- NUMBER (Z) (A) K 19 39 19 20 19 Mg 12 24 12 12 12 P 15 31 15 16 15 Si 14 28 14 14 14 Ar 18 40 18 22 18 Isotopes ISOTOPES are atoms of the same element that have the same number of protons but different number of neutrons. Other Common Isotopes and Their Uses CARBON has three naturally occurring isotopes. C-12 is the most common isotope of carbon. C-13 is commonly used in studying the structure of organic compounds using magnetic resonance spectroscopy. C-14 is a radioactive isotope used in carbon dating to determine the age of materials like historical artifacts. Unstable isotopes are called radioisotopes or radionucleotides. They emit radiation. Such atoms are described as radioactive and the process of emission of radiation is called RADIOACTIVE DECAY.  P-32 which is incorporated into nutrients giving information on metabolic pathways and used for detecting of skin cancer. I-131 which is used in medical diagnostic tests and treatment of illnesses of the thyroid gland. Cu-64 which is used in studying brain tumors. Fe-55 which is used as an X-ray source for different methods of scientific analysis. Na-24 which is used for detecting blood clots and tumors. Co-60 and Cs-137 which are used for the radiation therapy of cancer.  Exercises: Identify the element described in each statement. 1.An element with 26 protons and 30 neutrons. 2.Has a mass number of 23 and an atomic number of 11 3.Has 117 neutrons and an atomic number of 78 4.Has 125 neutrons and an atomic number of 85 Molecules and Ions Molecules MOLECULES are made up of atoms that are chemically bonded together. DIATOMIC MOLECULES contain only two atoms and normally occur in nature. If the atoms are of the same element, they are called HOMONUCLEAR. If they are of different elements, they are called HETERONUCLEAR. Homonuclear diatomic molecules examples: H2, Cl2, and Br2. Heteronuclear diatomic molecules examples: HCl, NO, and HF. On the other hand, a polyatomic molecule contains three or more atoms. Examples: O3, CO2, and C2H2. Ions IONS are atoms or molecules that have charge. Ions with positive charge are called CATIONS while ions with negative charge are called ANIONS.  Exercises: Determine whether the following are ATOMS, MOLECULES, or IONS. 1.Ne 2.NO3 3.O-2 4.K+ 5.HPO4-2 Chemical Formulas Structural formula Indicates how the atoms are arranged and bonded chemically. Molecular Formula A formula that shows the number of atoms per element present in a compound. C6H12O6 Empirical Formula Shows the simplest form of the atomic ratio in a chemical compound. CH2O Models A representation of a compound’s structure in a molecular view. It is a 3-dimensional view of the compound. The BALL-AND STICK model depicts a three-dimensional view of the atoms of a compound and the bonds between them. The SPACE-FILLING MODEL depicts the atoms of the compound using spheres that are joined together, approximating the proportionate sizes of the atoms. WATER H2 0 HMOLECULAR 0 2FORMULA EMPIRICAL FORMULA STRUCTURAL FORMULA SPACE-FILLING MODEL BALL-AND-STI CK MODEL CARBON DIOXIDE CO2 CO2 ACETYLENE C2H2 CH HYDROGEN PEROXIDE H2 0 2 H0  Exercises: Determine the empirical formulas of the following compounds given their molecular formulas. 1. Benzene (C6H6) 2. Ascorbic acid (C6H8O6) 3. Sucrose (C12H22O11) 4. Naphthalene (C10H4) 5. Hydrochloric acid (HCl)  Exercises: Construct the ball-and-stick model and the space-filling model of the following structural formulas. 1. Chloroform 2. 2-pentene Acetic Acid: Naming Compounds Review… What is the difference between Ionic compound and Covalent/Molecular compound? Naming Ionic Compounds An IONIC COMPOUND is a neutrally-charged compound that contains a cation that are usually metallic and anion that are usually non-metallic. Rules: a. Name the metal b. If the metal has more than one oxidation state, indicate the charge of the metal cation using Roman numerals and enclose it in parentheses or use suffixes –ous and –ic. c. If the anion is monoatomic, add the suffix –ide to the root of the name of the non-metal. A MONOATOMIC ANION is made up of only one atom. A POLYATOMIC ANION is made up of more than one atom of different elements. The Relationship between the Names of Oxoanions and the Number of Oxygen Atoms Present Naming Molecular Compounds A molecular compound is 1 mono- composed of non-metallic elements. 2 di- Rules: 3 tri- 4 tetra- 1. Use prefixes for both elements in 5 penta- the compound to indicate the 6 hexa- number of atom for each 7 hepta- elements present in the 8 octa- compound. If there is only 1 atom 9 nona- in the first element, the prefix 10 deca- “mono” is usually dropped. 2. Add the suffix –ide to the root of the name of the second element. Example… Nomenclature of Acids Nomenclature of Bases Most strong bases contain hydroxide (OH-), a polyatomic ion. Therefore, strong bases are named following the rules for naming ionic compounds. For example, NaOH is sodium hydroxide, KOH is potassium hydroxide, and Ca(OH)2 is calcium hydroxide. Weak bases made of ionic compounds are also named using the ionic naming system. For example, NH4OH is ammonium hydroxide. Weak bases are also sometimes molecular compounds or organic compounds because they have covalent bonds. Therefore, they are named following the rules for molecular or organic compounds. For example, methyl amine (CH3NH2) is a weak base. Some weak bases have “common” names. For example, NH3 is called ammonia; its name isn’t derived from any naming system. Write the empirical formula for the simplest binary ionic compound formed from each ion or element pair. 3+ 3− Ga and As 3+ 2− Eu and O calcium and chlorine Write the systematic name for each ionic compound: LiCl MgSO4 (NH4)3PO4 Cu2O What is the chemical name of the following Ionic compounds KCl KNO3 FeI2 Cu(NO3)2 Write the chemical formula of the following ionic compounds. Sodium hydroxide Aluminum phosphate  What is the chemical name of the following molecular compounds. 1. SF6 2. P2S3 Write the chemical formula of the following molecular compounds. 1. Carbon tetrafluoride 2. Diphosphorus pentoxide  Give the chemical name or formula of the following molecular compounds. 1.SO3 2.S2F10 3.SeCl6 4.Nitrogen trihydride 5.Phosphorus pentachloride