GENCHEM1_WEEK3_ION^JMOLECULES^JCOMPOUNDFORMATION_STUDENTSCOPY (3).pdf

The Periodic Table of Elements Definitions: Metals: Metals are elements that typically exhibit high electrical and thermal conductivity, luster, and malleability. They tend to lose electrons in chemical reactions, forming positive ions or cations. Most metals are solid at room tem...

The Periodic Table of Elements Definitions: Metals: Metals are elements that typically exhibit high electrical and thermal conductivity, luster, and malleability. They tend to lose electrons in chemical reactions, forming positive ions or cations. Most metals are solid at room temperature (except mercury, which is liquid). Nonmetals: Nonmetals are elements that lack the characteristics of metals. They are generally poor conductors of heat and electricity, have lower density, and are not lustrous. Nonmetals can be gases, liquids, or solids at room temperature. They tend to gain electrons during chemical reactions, forming negative ions or anions. Metalloids: Metalloids, also known as semimetals, are elements with properties intermediate between metals and nonmetals. They can exhibit varying degrees of electrical conductivity and are often semiconductors. Metalloids can behave as either metals or nonmetals depending on the conditions. Classification Based on the Periodic Table Image: Example: Chlorine is a well-known halogen found in the periodic table. Here are the details about chlorine based on the provided periodic table: Chlorine (Cl): (a) What is its symbol? Symbol: Cl (b) In which period and in which group is the element located? Period: 3 Group: 17 (VIIA in older notations) (c) What is its atomic number? Atomic Number: 17 (d) Is it a metal or nonmetal? Type: Nonmetal Additional Information: Chlorine is part of the halogens group, which includes other elements such as fluorine, bromine, iodine, and astatine. Halogens are located in Group 17 of the periodic table, known for being highly reactive, especially with alkali metals and alkaline earth metals to form salts. Chlorine itself is a diatomic molecule under standard conditions and is used extensively in water purification, disinfectants, and as a component in many household and industrial chemicals. Ions, Molecules, and Naming Compounds  Ions Ions: Atoms or molecules that carry a net charge due to the loss or gain of electrons. Cations: Positively charged ions Anions: Negatively charged ions Molecules: Groups of two or more atoms held together by chemical bonds (H 2, CO2). Note: 1. When atom loses electrons, they become positively charged. 2. When atom gains electrons, they become negatively charged. In general, metal atoms tend to lose electrons to form cations and nonmetal atoms tend to gain electrons to form anions. Thus, ionic compounds tend to be composed of both metal cations and nonmetal anions, as in NaCl. The net charge on an ion is represented by a superscript. The superscripts +, 2+, and 3+, for instance, mean a net charge resulting from the loss of one, two, and three electrons, respectively. The superscripts -, 2-, and 3- represent net charges resulting from the gain of one, two, and three electrons, respectively. Chlorine, with 17 protons and 17 electrons, for example, can gain an electron in chemical reactions, producing the Cl- ion: In general, metal atoms tend to lose electrons to form cations and nonmetal atoms tend to gain electrons to form anions. Thus, ionic compounds tend to be composed of both metal cations and nonmetal anions, as in NaCl Subscripts and superscripts can be added to an element’s symbol to specify a particular isotope of the element and provide other important information. The atomic number is written as a subscript on the left of the element symbol, the mass number is written as a superscript on the left of the element symbol, and the ionic charge, if any, appears as a superscript on the right side of the element symbol. If the charge is zero, nothing is written in the charge position. If the charge is +1 or −1, the convention is to write + or − (without the 1) as a superscript on the right. If the charge is +2, +3, −2, or −3, we write 2+, 3+, 2−, or 3− as the superscripts.  Writing Chemical Symbols for Ions 1. Give the chemical symbol, including superscript indicating mass number, for (a) the ion with 22 protons, 26 neutrons, and 19 electrons; and (b) the ion of sulfur that has 16 neutrons and 18 electrons.  Ionic Compounds Ionic compounds are generally combinations of metals and nonmetals, as in NaCl  Ionic Compounds Note: 1. The ions in ionic compounds are arranged in three-dimensional structures 2. the ions in an ionic compound always occur in such a ratio that the total positive charge equals the total negative charge 3. if the charges on the cation and anion are equal, the subscript on each ion is 1. If the charges are not equal, the charge on one ion (without its sign) will become the subscript on the other ion.  Ionic Compounds Note: Remember that the empirical formula should be the smallest possible whole-number ratio of the two elements. So, the empirical formula for the ionic compound formed between and is rather than  Ionic Compounds The empirical formula of a compound represents the simplest whole-number ratio of atoms of each element present in the compound. To determine the empirical formula of a compound formed between tungsten ( ) and oxygen , we need to balance the charges of the ions to achieve electrical neutrality.  Formation of Ions: Electron Transfer: Atoms gain or lose electrons to achieve noble gas configuration. Example: Sodium (Na) loses an electron to form Na + , while chlorine (Cl) gains an electron to form Cl −. Ionic Bonds: Electrostatic forces of attraction between oppositely charged ions form ionic compounds. Example: Formation of sodium chloride (NaCl) from Na + and Cl −.  Properties of Ions and Ionic Compounds: High melting and boiling points. Conduct electricity when dissolved in water or molten.  Molecules and Molecular Compounds A molecule made up of two atoms is called a diatomic molecule. Compounds composed of molecules contain more than one type of atom and are called molecular compounds. Most of the molecular substances we will encounter contain only nonmetals.  Molecular and Empirical Formulas Chemical formulas that indicate the actual numbers of atoms in a molecule are called molecular formulas. Chemical formulas that give only the relative number of atoms of each type in a molecule are called empirical formulas. The subscripts in an empirical formula are always the smallest possible whole-number ratios.  Formation of Molecules: Covalent Bonds: Sharing of electron pairs between atoms. Example: Water (H 2O ) formed by sharing electrons between hydrogen and oxygen. Molecular Compounds: Composed of molecules formed by covalent bonds. Generally, it have lower melting and boiling points compared to ionic compounds.  Formation of Molecules: Covalent Bonds: Sharing of electron pairs between atoms. Example: Water (H 2O ) formed by sharing electrons between hydrogen and oxygen.  Compound Formation Types of Compounds: Ionic Compounds: Molecular Compounds:  Compound Formation Types of Compounds: Stoichiometry of Compounds: Empirical and molecular formulas indicate the ratio and actual number of atoms in a compound.  Compound Formation Write the empirical formulas for (a) glucose, a substance also known as either blood sugar or dextrose—molecular formula C6H12O6; (b) nitrous oxide, a substance used as an anesthetic and commonly called laughing gas—molecular formula N2O Naming Compounds Naming Compounds Naming Compounds Naming Compounds  Practice Problems 1. Name the following compounds: 2. Write the formulas for the following compounds: Barium sulfate Dinitrogen trioxide Aluminum phosphate Iron(II) chloride Sodium carbonate Practice Problems