CHEM1405 LAB4

.pdf

School

Lone Star College System, ?Montgomery *

*We aren’t endorsed by this school

Course

1405

Subject

Chemistry

Date

Oct 30, 2023

Type

pdf

Pages

Uploaded by EarlMusic12170

Lab 4: Chemical Symbols and NomenclatureIntroductory Chemistry – Prof. Martinez I. Objectives • To learn about chemical symbols of atoms and isotopes • To practice naming ionic and molecular compounds II. Introduction Part 1: Atoms ______________________________________________________________________ Atoms are the submicroscopic particles that constitute the fundamental building blocks of ordinary matter. The atomic model states that atoms have three subatomic particles which are electrons, neutrons, and protons. The Atomic Number (Z) is the number of protons in the nucleus of the atom and also defines the element. For example, any atom with 6 protons is Carbon, and any atom with 8 protons is oxygen. Since atoms are electrically neutral the atomic number also equals the number of electrons unless otherwise stated. The Mass number (A) is the total number of protons and neutrons in an atom. Figure 1 displays how the chemicals are symbolized and how they incorporate mass number and atomic number. Figure 1. Chemical symbols Part 2: Chemical Nomenclature_________________________________________________________ Free atoms are rare in nature; instead they bind together in specific geometrical arrangements to form molecules. All the atoms in a molecule move as one unit. The naming of compounds is called chemical nomenclature. It is a very specific process, depending on the type of compound. The rest of this introduction section describes how to name ionic compounds, molecular compounds, hydrates, and acids. Nomenclature of Ionic Compounds Ionic compounds are composed of ions. An ion is an atom or molecule with an electrical charge. Monatomic ions are formed from single atoms that have gained or lost electrons. Polyatomic ions are formed from molecules (groups of atoms bonded together) that have gained or lost electrons. Atomic number (Z) = number of protons = number of electrons (if neutral) (4.1) mass number (A) = number of protons + number of neutrons (4.2) A – Z = number of neutrons (4.3) All labs written using collective resources shared by numerous Lone Star College System Chemistry Faculty. For more information, please contact me at Esmeralda.Martinez@lonestar.edu

Lab 4: Chemical Symbols and NomenclatureIntroductory Chemistry – Prof. Martinez Negative ions are called anions, and are formed when an atom or molecule gains electrons. All non- metals form negatively charged ions. Positive ions are called cations, and are formed when an atom or molecule loses electrons. All metals form positively charged cations. Ions with opposite charges (positive metal cations and negative non-metal anions) will experience a strong electrostatic attraction and form an ionic bond, which leads to the formation of the ionic compound. Non-metal Anions Non-metals will form anions with only one possible negative charge. The following Periodic Table shows the charges for non-metal anions commonly found in ionic compounds: Note that • The magnitude of the negative charges on these anions is equal to 8 minus their Group Number. • The names of these anions are based on the element names, but the endings are all changed to –ide. Metal Cations Most (but not all) main group metals will form cations with only one possible charge. Most (but not all) transition metals will form cations with more than one possible charge. The following Periodic Table shows the charges for metal cations commonly found in ionic compounds: Example 4.1 Sulfur in Group 6A forms anions with a [8–6]=2, or, –2 charge. Example 4.2 The Cl -1 anion is called the chloride ion. All labs written using collective resources shared by numerous Lone Star College System Chemistry Faculty. For more information, please contact me at Esmeralda.Martinez@lonestar.edu

Lab 4: Chemical Symbols and NomenclatureIntroductory Chemistry – Prof. Martinez Note that • The magnitude of the positive charge on the main group metal cations is generally equal to their Group Number. • The names of metal cations with only one possible charge are the same as the names of the metals themselves. • For metal cations with more than one possible charge, the ion charge must be indicated in the ion name. In the IUPAC system, the ion charge is indicated in the name as Roman numerals in brackets. Polyatomic Ions Polyatomic ions are formed from molecules (groups of atoms bonded together) that have gained or lost electrons. The table below includes a list of common polyatomic ions. Example 4.3 Magnesium in Group 2A forms cations with a +2 charge. Example 4.4 Al +3 is called the aluminum cation. Ag +1 is called the silver cation. Example 4.5 Pb +2 is called the lead(II) cation. Pb +4 is called the lead(IV) cation. OH − 1 Hydroxide O 2 − 2 Peroxide CN − 1 Cyanide CO 3 − 2 Carbonate SCN − 1 Thiocyanate SO 3 − 2 Sulfite HCO 3 − 1 Bicarbonate (Hydrogen Carbonate) SO 4 − 2 Sulfate All labs written using collective resources shared by numerous Lone Star College System Chemistry Faculty. For more information, please contact me at Esmeralda.Martinez@lonestar.edu

Lab 4: Chemical Symbols and NomenclatureIntroductory Chemistry – Prof. Martinez Note that • Almost all the polyatomic ions are negatively charged anions. • Most of the names of polyatomic anions end in either –ate or –ite. The –ate’s always have one more oxygen than the -ite’s. Formulas and Names of Ionic Compounds Ionic compounds are formed when positive cations and negative anions are attracted to each other via strong electrostatic forces. This attraction is called an ionic bond. The following are the basic rules for writing the formulas and names of ionic compounds: Writing Formulas 1. Determine the formulas and charges on the cation and anion involved in the compound. 2. Combine the ions in a ratio that results in the formation of a neutral ionic compound. In other words, the total charge of all the positive cations must equal the total charge of all the negative anions in the compound. The numbers of each element present in the compound are shown as subscripts after the element symbol. Writing Names 1. Both the cation and anion must be named. 2. Always name the cation first, then the anion. HSO 3 − 1 Bisulfite (Hydrogen Sulfite) S 2 O 3 − 2 Thiosulfate HSO 4 − 1 Bisulfate (Hydrogen Sulfate) C 2 O 4 − 2 Oxalate C 2 H 3 O 2 − 1 Acetate CrO 4 − 2 Chromate NO 2 − 1 Nitrite Cr 2 O 7 − 2 Dichromate NO 3 − 1 Nitrate MnO 4 − 1 Permanganate PO 3 − 3 Phosphite ClO − 1 Hypochlorite PO 4 − 3 Phosphate ClO 2 − 1 Chlorite ClO 3 − 1 Chlorate NH 4 +1 Ammonium ClO 4 − 1 Perchlorate Hg 2 +2 Mercury (I) Example 4.6 Sulfate, SO 4 − 2 , has one more oxygen atom present than sulfite, SO 3 − 2 . All labs written using collective resources shared by numerous Lone Star College System Chemistry Faculty. For more information, please contact me at Esmeralda.Martinez@lonestar.edu

Lab 4: Chemical Symbols and NomenclatureIntroductory Chemistry – Prof. Martinez Note in the above Example 9 that parentheses are placed around the polyatomic portion of compound, to indicate that it must be treated as a complete and whole unit. Example 4.7: Write the formula and name for the compound formed between calcium and fluorine Ca (metal) forms a +2 cation Ca +2 , the calcium cation. F (non-metal) forms a -1 anion F − 1 , the fluoride anion. To obtain a neutral compound, 1 Ca +2 is needed for every 2 F − 1 The formula of the compound is CaF 2 The name of the compound is Calcium Fluoride Example 4.8: Write the formula for iron(III) chloride. First identify the cation and the anion in this compound. Cation = iron(III) = Fe +3 (transition metal cation) Anion = chloride = Cl − 1 (non-metal anion) To obtain a neutral compound, 1 Fe +3 is needed for every 3 Cl − 1 The formula of the compound is FeCl 3 Example 4.9: Write the formula for magnesium phosphate. First identify the cation and anion in this compound. Cation = magnesium = Mg +2 (metal cation) Anion = phosphate = PO 4 − 3 (polyatomic anion) To obtain a neutral compound, 3 Mg +2 are needed for every 2 PO 4 − 3 The formula of the compound is Mg 3 (PO 4 ) 2 Example 4.10: Name the ionic compound Al(NO 3 ) 3 First identify the cation and anion in this compound. Cation = Al +3 = the aluminum cation (metal cation) Anion = NO 3 − 1 = the nitrate anion (polyatomic anion) The name of this compound is Aluminum Nitrate All labs written using collective resources shared by numerous Lone Star College System Chemistry Faculty. For more information, please contact me at Esmeralda.Martinez@lonestar.edu

Lab 4: Chemical Symbols and NomenclatureIntroductory Chemistry – Prof. Martinez Nomenclature of Simple Covalent Compounds Covalent compounds are compounds formed between non-metals only. Simple binary covalent compounds contain just two different types of non-metal elements. When non-metals combine they can form several different covalent compounds. These compounds must therefore be identified with unique names and formulas. Formulas and Names of Simple Covalent Compounds 1. Always write/name the element with more metallic character first. Metallic character increases going from right to left, and top to bottom on the Periodic Table. 2. Then write/name the second (less metallic) element, changing the ending of its name to -ide. 3. Since nonmetals often combine in different proportions to form a number of different compounds, prefixes must be included in the names to indicate the numbers of each kind of atom present.Prefixes for 1-10 atoms are given in the following table. Example 4.11: Name the compound TiO 2 First identify the cation and anion in this compound. Cation = Ti +4 = the titanium(IV) cation (transition metal cation) Anion = O − 2 = the oxide anion (non-metal anion) The name of the compound is Titanium(IV) Oxide Example 4.12: Carbon and oxygen combine to form two common covalent compounds CO 2 and CO. Number Prefix Number Prefix 1 Mono 6 Hexa 2 Di 7 Hepta 3 Tri 8 Octa 4 Tetra 9 Nona 5 Penta 10 Deca Example 4.13: A compound contains 3 atoms of sulfur and 4 atoms of phosphorus. Write its name and formula. Since phosphorus is the more metallic element (left of sulfur), it must be named first. Sulfur being the less metallic element is named second with an -ide ending = sulfide . The prefix for three is tri , and the prefix for four is tetra . The name of this compound is tetraphosphorus trisulfide The formula of this compound is P 4 S 3 All labs written using collective resources shared by numerous Lone Star College System Chemistry Faculty. For more information, please contact me at Esmeralda.Martinez@lonestar.edu

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version