Unit 1 - Foundations of Chemistry

Transcription

1 Unit 1 - Foundations of Chemistry Chapter 1 - Atomic Structure and Nomenclature Watch: An Introduction to Chemistry Mr. Palmarin Chapter 1 - Nomenclature 1 / 47

2 Section Introduction to Chemistry What is Chemistry? Chemistry is the study of the properties of materials and the changes that materials undergo. Mr. Palmarin Chapter 1 - Nomenclature 2 / 47

3 Why study Chemistry? It is the central science, leading to a fundamental understanding of other sciences and technologies. It is an extremely practical science that greatly impacts our daily living: improvement to health care conservation of natural resources protection of the environment provision of our everyday needs for food, clothing, and shelter Using chemistry, we have discovered helpful pharmaceutical chemicals, increased food production, and developed plastics. Mr. Palmarin Chapter 1 - Nomenclature 3 / 47

4 Classifications of Matter Matter is the physical material of the universe. We can classify matter in the following ways: Mr. Palmarin Chapter 1 - Nomenclature 4 / 47

5 Classifications of Matter The tremendous variety of matter in our world is due to the combinations of only about 100 very basic substances called elements. Chemistry attempts to understand the properties of matter in terms of atoms. Summary: All matter is composed of elements. All elements are composed of very small particles called atoms. What are atoms made up of? Mr. Palmarin Chapter 1 - Nomenclature 5 / 47

6 Atomic structure: Atoms contain two main regions called the nucleus and the electron cloud. The nucleus is composed of two subatomic particles called protons and neutrons. The electron cloud is composed of one subatomic particle called the electron. (a) The Bohr Model - a convenient model that accurately predicts how atoms will behave (b) The Electron Cloud Model - this model most accurately reflects reality Mr. Palmarin Chapter 1 - Nomenclature 6 / 47

7 Pure Substances A pure substance is matter that has distinct properties and a composition that doesn t vary from sample to sample. Examples: Water Oxygen Table salt All substances are either elements or compounds. Elements are composed of only one kind of atom (ex: O, H, Fe). Compounds are substances composed of two or more elements (water, table salt). Mr. Palmarin Chapter 1 - Nomenclature 7 / 47

8 A molecule is essentially a group of atoms bonded together. Note: Molecules of elements consist of two or more similar atoms. Molecules of compounds consist of two or more different atoms. Figure: Brown et al; Chemistry: The Central Science; p. 8 Mr. Palmarin Chapter 1 - Nomenclature 8 / 47

9 Section The Periodic Table Periodic Table - A structured arrangement of elements that allows us to explain and predict physical and chemical properties. Note: You can print off a copy of the periodic table and a sheet of common ions from the Moodle. Mr. Palmarin Chapter 1 - Nomenclature 9 / 47

10 Symbols on the Periodic Table Mr. Palmarin Chapter 1 - Nomenclature 10 / 47

11 Charges The charges of the three key subatomic particles: Protons - Positively charged. Denoted: p + Neutrons - Neutrally charged. Denoted: n 0 Electrons - Negatively charged. Denoted: e Elements on the Periodic Table are in electronically neutral form; i.e. they carry no charge. To be electronically neutral, an atom must have an equal number of protons and electrons. Example: Which atom below is electronically neutral? Mr. Palmarin Chapter 1 - Nomenclature 11 / 47

12 Ions The nucleus of an atom is unchanged by chemical processes, but atoms can readily gain or lose electrons. An ion is formed when electrons are removed from or added to a neutral atom. An anion is a negatively charged ion. A cation is a positively charged ion. Example: How many electrons does Na + have? Mr. Palmarin Chapter 1 - Nomenclature 12 / 47

13 Practice: How many electrons does Cl have? What type of ion is Cl? Mr. Palmarin Chapter 1 - Nomenclature 13 / 47

14 Predicting Ionic Charges General rule: Metal atoms tend to lose electrons to form cations, whereas nonmetal atoms tend to gain electrons to form anions. Figure: The red line divides metals from nonmetals. It also separates cations from anions. Mr. Palmarin Chapter 1 - Nomenclature 14 / 47

15 How Elements Form Compounds Much of chemical activity involves the transfer of electrons from one substance to another. Ionic compounds are generally combinations of metals and nonmetals. These compounds are held together by attractions between opposite charged ions (like a magnetic attraction). This is called an ionic bond. Molecular compounds are generally composed of nonmetals only. Electrons are shared between atoms. This is called a covalent bond. Examples: 1 MgCl 2 (magnesium chloride) 2 H 2 O (water) Mr. Palmarin Chapter 1 - Nomenclature 15 / 47

16 Mr. Palmarin Chapter 1 - Nomenclature 16 / 47

17 Homonuclear Molecules These are molecules composed of only one type of element. The most common are: Acronym: PS HOFBrINCl P 4 S 8 H 2 O 2 F 2 Br 2 I 2 N 2 Cl 2 For example: Why would two chlorine atoms share a pair of electrons to form a covalent bond? Notice how they both have 7 electrons in their outer orbit (valence shell). If they both gain 1 electron, they will be stable (8 outer electrons is ideal). Mr. Palmarin Chapter 1 - Nomenclature 17 / 47

18 Polyatomic Ions Polyatomic ions - groups of atoms that tend to stay together and carry an overall ionic charge. Examples: nitrate - NO 3 hydroxide - OH bicarbonate - HCO 3 chlorate - ClO 3 sulfate - SO4 2 phosphate - PO4 3 Mr. Palmarin Chapter 1 - Nomenclature 18 / 47

19 Note: You can print off a copy of the periodic table and a sheet of common ions from the Moodle. Mr. Palmarin Chapter 1 - Nomenclature 19 / 47

20 Section Naming Ionic Compounds Steps for naming binary ionic compounds: 1 Name the metal (cation) first. 2 Name the nonmetal (anion) second. For the nonmetal, drop the ending and add ide. 3 Use Roman Numerals in parentheses to indicate which charge of the metal is used. This is only used for metals that make more than one charge. Mr. Palmarin Chapter 1 - Nomenclature 20 / 47

21 Examples: 1) Ca 3 N 2 calcium nitride 2) Mg 3 P 2 magnesium phospide 3) Al 2 O 3 aluminum oxide 4) CuCl 2 Look on your periodic table. Notice how copper makes more than one charge (2+ or 1+). Recall how compounds are electronically neutral. Since chlorine always makes a 1 charge (and there are two chlorine atoms), this implies that copper must be taking a 2+ charge in this situation. copper (II) chloride 5) FeBr 3 Similar to 4) iron (III) bromide 6) CoN N takes 3 and we have one nitrogen and one cobalt atom. Cobalt is taking a 3+ to make the compound neutral cobalt (III) nitride Mr. Palmarin Chapter 1 - Nomenclature 21 / 47

22 Practice: Name the following compounds. [See Section 1.3 Video] 1) CaCl 2 2) MgBr 2 3) FeI 3 4) CuCl 2 5) Cr 3 N 2 6) BeO Mr. Palmarin Chapter 1 - Nomenclature 22 / 47

23 Steps for naming ionic compounds with polyatomic ions: 1 For polyatomic compounds, name the metal first followed by the name of the polyatomic ion. The endings do not change. Don t forget about metals that make more than one charge. Examples: 1) Al(OH) 3 The OH compound is called hydroxide (see the back of your periodic table - your sheet of polyatomic ions). Therefore aluminum hydroxide 2) NaHCO 3 Similar to 1) sodium bicarbonate 3) Sn(NO 3 ) 4 NO 3 is called nitrite. But notice how Sn (tin) takes two charges (2+ or 4+). Therefore, we need to use roman numerals. Nitrite takes a 1 charge; therefore, tin is taking a 4+ charge in this situation. tin (IV) nitrite Mr. Palmarin Chapter 1 - Nomenclature 23 / 47

24 Practice: Name the following compounds. [See Section 1.3 Video] 1) KNO 3 2) Mg 3 (PO 4 ) 2 3) NaOH 4) Pb(NO 2 ) 4 Mr. Palmarin Chapter 1 - Nomenclature 24 / 47

25 Writing Formulas for Ionic Compounds Steps: 1 Write the ionic charges above the symbols. 2 Determine the lowest number of each element that would make the entire compound electronically neutral. i.e. Crisscross the numbers, using them as subscripts. Remember to reduce when appropriate. Key fact: The sum of the charges on the positive ions equals the sum of the charges on the negative ions. Mr. Palmarin Chapter 1 - Nomenclature 25 / 47

26 Examples: 1) calcium iodide Step 1: Ca 2+ I Step 2: We need exactly 2 iodine atoms to cancel out calcium s 2+ charge CaI 2 Note: Crisscrossing the charges would have given the same result. Here, no reducing is necessary. 2) sodium phosphide = Na + P 3 (we need 3 sodiums to cancel out phosphorus 3- charge) Na 3 P 3) calcium chloride = CaCl 2 Mr. Palmarin Chapter 1 - Nomenclature 26 / 47

27 Practice: Write the formulas for the following compounds. [See Section 1.3 Video] 1) sodium bromide 2) strontium nitride 3) potassium phosphide 4) magnesium nitride 5) zinc iodide Mr. Palmarin Chapter 1 - Nomenclature 27 / 47

28 Note: Some metals can make more than one kind of ion. Roman numerals in brackets indicate the charge of the ion (not how many are in the formula). On your periodic table (if you printed in colour), the common charges are listed in red. Examples: 1) iron (III) oxide Step 1: Fe 3+ O 2 Step 2: Here, we need exactly 2 Fe atoms and 3 O atoms to arrive at an electronically neutral compound Fe 2 O 3 2) iron (II) oxide Step 1: Fe 2+ O 2 Step 2: Here, we need exactly 1 Fe atom and 1 O atom to arrive at an electronically neutral compound FeO Note: If you are using the crisscross method you must reduce the numbers; i.e. Fe 2 O 2 reduces to FeO. Mr. Palmarin Chapter 1 - Nomenclature 28 / 47

29 Practice: Write the formulas for the following compounds. [See Section 1.3 Video] 1) cobalt (II) chloride 2) nickel (III) oxide 3) lead (IV) selenide 4) tin (II) nitride 5) iron (III) phosphide Mr. Palmarin Chapter 1 - Nomenclature 29 / 47

30 Note: Ionic compounds may include polyatomic ions. Reference the List of Polyatomic Ions to determine the charges of the polyatomic ions. Remember to put the entire polyatomic ion in brackets if you need more than one! Examples: 1) sodium carbonite Step 1: Na + CO 2 2 Step 2: We need exactly 2 Na atoms and 1 CO 2 molecules to arrive at an electronically neutral compound Na 2 CO 2 2) aluminum sulfate Step 1: Al 3+ SO 2 4 Step 2: We need exactly 2 Al atoms and 3 SO 4 molecules to arrive at an electronically neutral compound Al 2 (SO 4 ) 3 Note: Brackets are used to indicate that there are 3 SO 4 molecules. Mr. Palmarin Chapter 1 - Nomenclature 30 / 47

31 Practice: Write the formulas for the following compounds. [See Section 1.3 Video] 1) sodium chlorate 2) magnesium phosphate 3) silver nitrate 4) barium sulfite 5) iron (II) nitrite Mr. Palmarin Chapter 1 - Nomenclature 31 / 47

32 Section Molecular Compounds Molecular compound - formed when nonmetals (anions) share electrons with other nonmetals (anions). Covalent bond - a shared pair of electrons held between two nonmetal atoms that holds the atoms together. Mr. Palmarin Chapter 1 - Nomenclature 32 / 47

33 Writing Formulas for Molecular Compounds Steps: 1 Write the symbols of each nonmetal. 2 Write the appropriate subscripts for each nonmetal that corresponds to the prefixes used. Note: The prefix mono is never used on the first nonmetal. mono di tri tetra penta hexa hepta octa nona deca Note: This list will not be given to you on the exam(s). Either commit to memory, or write this on the top of your periodic table. Mr. Palmarin Chapter 1 - Nomenclature 33 / 47

34 Examples: Write the formulas for the following molecular compounds. 1) carbon dioxide No prefix in front of carbon implies there is one carbon. The prefix di implies there are two oxygen atoms. CO 2 2) dinitrogen trioxide N 2 O 3 3) carbon tetrafluoride CF 4 Mr. Palmarin Chapter 1 - Nomenclature 34 / 47

35 Practice: Write the formulas for the following molecular compounds. [See Section 1.4 Video] 1) dihydrogen monoxide 2) diboron trioxide 3) phosphorus trihydride Mr. Palmarin Chapter 1 - Nomenclature 35 / 47

36 Writing Names for Molecular Compounds Steps: 1 Write the name of the first nonmental and then the second. 2 Place the appropriate prefixes in front of each of the names. The prefixes correspond to the subscripts of each element. 3 Drop the ending of the last element named and add -ide. Note: Sometimes prefixes are shortened when the ending vowel of the prefix conflicts with a starting vowel in the compound. This makes the name easier to pronounce. For example: tetraoxide is typically written as tetroxide or monooxide is shortened to monoxide. Mr. Palmarin Chapter 1 - Nomenclature 36 / 47

37 Examples: Name the following molecular compounds. 1) CS 2 carbon disulfide Recall: The prefix mono is never used for the first element. 2) N 2 O 4 dinitrogen tetroxide Recall: tetraoxide is shortened to tetroxide. This avoids two vowels being next to each other. 3) P 4 S 10 tetraphosphorus decasulfide Practice: Name the following molecular compounds. [See Section 1.4 Video] 1) CO 2) CF 4 3) C 2 H 6 Mr. Palmarin Chapter 1 - Nomenclature 37 / 47

38 Section Acids An acid is a substance whose molecules yield hydrogen ions (H + ) when dissolved in water. An acid is composed of H + ions connected to an anion (negative ion). The number of H + ions is equal to the charge of the anion. Example: SO 2 4 requires two H + ions = H 2 SO 4 H 2 SO 4 is called sulfuric acid. Note: acids always start with H bonded to an anion. How do we name acids? Mr. Palmarin Chapter 1 - Nomenclature 38 / 47

39 There are three kinds of acids: Type 1: Acids containing anions whose names end in -ide are named by changing the -ide ending to -ic, adding the prefix hydro- to this anion name, and then following with the word acid. Examples: 1) HCl Notice hydrogen is out front (therefore this is an acid) and how the anion (chloride) ends in ide. Therefore, this is a Type 1 acid = replace ide with ic and add the word acid hydrochloric acid 2) H 2 S This is an acid. Here, the anion is sulfide. Now, this will not turn into sulfic acid. There are two exceptions (sulfur and phosphorus). In these examples, we will add a vowel (this is definitely strange, but it s simply the convention). hydrosulfuric acid Mr. Palmarin Chapter 1 - Nomenclature 39 / 47

40 Type 2: Anions that end in -ate are named by changing -ate to -ic and then adding the word acid. Type 3: Anions that end in -ite are named by changing -ite to -ous and then adding the word acid. Phrase: ate - ic; ite - ous Examples: 1) HClO 3 Reference your list polyatomic ions. ClO 3 is chlorate. Therefore, ate is changed to ic. chloric acid 2) H 2 SO 4 sulfuric acid 3) HNO 2 nitrous acid 4) H 3 PO 4 phosphoric acid Recall: Here was the second except; i.e. we add an extra vowel. Mr. Palmarin Chapter 1 - Nomenclature 40 / 47

41 Practice: Name the following acids. 1) HI [See Section 1.5 Video] 2) HIO 3 3) HIO 2 4) H 3 P 5) H 3 PO 3 Mr. Palmarin Chapter 1 - Nomenclature 41 / 47

42 Writing Formulas for Acids Steps: 1 Use the same criss-cross method as with ionic compounds. 2 H + will always be at the start of your criss-cross. Note: The number of hydrogens out front will always be equal to the charge of the anion (negative ion). Mr. Palmarin Chapter 1 - Nomenclature 42 / 47

43 Examples: 1) hydrosulfuric acid Hydro implies type 1 = ic - ide and we re dealing with sulfur; S 2. Therefore, we require 2 H atoms to balance S s charge of 2 H 2 S 2) carbonic acid No hydro and ends in ic = type 2. Therefore, ic - ate. So we re dealing with carbonate; CO3 2 and so once again we will need 2 H s to balance the charge. H 2 CO 3 3) nitrous acid No hydro and ends in ous = type 3. Therefore, ous - ite. Nitrite is NO 2 and so we only need 1 H to balance that charge. HNO 2 Mr. Palmarin Chapter 1 - Nomenclature 43 / 47

44 Practice: Write formulas for the following acids. [See Section 1.5 Video] 1) chromic acid 2) carbonous acid 3) hydrochloric acid 4) oxalic acid 5) hydrocyanic acid Mr. Palmarin Chapter 1 - Nomenclature 44 / 47

45 Section Basic Organic Naming An organic compound is a compound that contains carbon. We will be using some basic organic compounds throughout the semester. These compounds will either be alkanes or alkenes. Alkane: Consist only of hydrogen and carbon. General formula: C n H 2n+2 ; i.e. all bonds are single bonds and each carbon atom is saturated with hydrogen. Ex: CH 4, C 2 H 6, C 3 H 8,... Alkene: Consist of exactly two carbons less than its corresponding alkane. General formula: C n H 2n ; i.e. there exists one double bonded carbon to carbon. Ex: C 2 H 4, C 3 H 6, C 4 H 8,... Mr. Palmarin Chapter 1 - Nomenclature 45 / 47

46 The organic naming system uses the following prefixes to identify the number of carbons. The ending ane or ene identifies the number of hydrogens (single bonds vs. double bond). meth eth prop but pent hex hept oct non dec Examples: Name the following alkanes/alkenes. 1) C 4 H 10 4 carbons = but. Is this ane or ene? 10 hydrogens comes from 2(4) + 2; i.e. 2n + 2 were n is the number of carbon atoms. 2n + 2 = alkane. butane 2) C 8 H H s = 2(8); i.e. 2n = alkene octene 3) C 6 H 18 hexane 4) C 8 H 18 (commonly called gasoline) octane Mr. Palmarin Chapter 1 - Nomenclature 46 / 47

47 Practice: Name or write the formula for the following organic compounds. [See Section 1.6 Video] 1) C 2 H 4 2) propane 3) C 4 H 8 4) pentene 5) decane Mr. Palmarin Chapter 1 - Nomenclature 47 / 47