GENERAL CHEMISTRY 1 2ND QUARTER WEEK 1 DEFINITION OF TERMS AND CONCEPTS: 1. AUFBAU PRINCIPLE - Electrons fill orbitals starting at the lowest available energy before filling higher states. 2. ELECTRONIC CONFIGURATION - Show the distribution of electrons of an atom or a molecule 3. PARAMAGNETISM - Refers to the magnetic state of an atom with one or more unpaired electrons. 4. DIAMAGNETISM - Refers to the magnetic state of an atom with one or more paired electrons. further experiments showed that Bohr’s model is fundamentally incorrect. TWO SCIENTISTS OF WAVE MODEL ● LOUIS VICTOR DE BROGIE ● ERWIN SCHRODINGER - - - Suggested it might be useful to find out whether the electron could be described as a wave. It introduced a mathematical description of the electron’s motion called a WAVE FUNCTION or ATOMIC ORBITAL. “Orbitals are nothing like orbits.” ERWIN SCHRODINGER THE QUANTUM MECHANICAL DESCRIPTION OF THE ATOM AND ITS ELECTRONIC STRUCTURE ● Scientists use models to help provide mental images for concepts that can be seen directly, like the atom. Since the time of the first use of the word atom, different models of an atom have been proposed. As new evidence on the properties and reactions of atoms is gathered. - NEILS HENDRIK DAVID BOHR - THE QUANTUM MECHANICAL MODEL OF THE ATOM - - At first, Bohr’s model appeared very promising. It fits the hydrogen atom very well. However, when this model was applied to atoms other than hydrogen, it did not work. In fact, A space in which electrons are likely to be found. Electrons WHIRL about the nucleus billions of times in one second. They are not moving around in random patterns. The location of electrons depends upon how much energy the electron has. SCHRODINGER’S EQUATION - Use of quantum numbers to describe each electron within an atom - corresponding to the orbital size, shape, and orientation in space. Later it was found that one needed a quantum number associated with electron spin. - f=3 QUANTUM NUMBERS - The set of numbers used to describe the position and energy of the electron in an atom. MAGNETIC QUANTUM NUMBER mℓ - It identifies the exact location of electrons in the degenerate orbitals. SPIN QUANTUM NUMBER ms - It designates the spin of the electron. There can be two values : +½ : -½ FOUR QUANTUM NUMBERS 1. PRINCIPAL QUANTUM NUMBERS (n) 2. ANGULAR MOMENTUM QUANTUM NUMBER (ℓ) 3. MAGNETIC QUANTUM NUMBER (mℓ) 4. SPIN QUANTUM NUMBER (ms) PRINCIPAL QUANTUM NUMBER n - ANGULAR MOMENTUM QUANTUM NUMBER ℓ - Designates the shell where an electron can be found. The values are whole numbers, which identify the shell. 1 to 7 1≤n 0≤ℓ≤n−1 It specifies the orbital type where the electron is located. - ⬆️ ⬇️ ASSIGNING THE FOUR QUANTUM NUMBERS - Write the electronic configuration of an element Draw the orbital diagram Identify the four-quantum number WHAT IS ELECTRONIC CONFIGURATION? - Shows the distribution of electrons of an atom or molecule. Significance of electronic configuration: - Show where the electrons are located - What element referring to - How many electrons it has - s=0 p=1 d=2 ELECTRONIC CONFIGURATION OF ELEMENTS The figure above shows one way of remembering the pattern of filling the atomic orbitals. The filling begins at the top of the pattern and follows the first arrow. When you reach the end of the first arrow, you go to the second arrow and follow it to the end. The third arrow continues the pattern. THE THREE RULES IN WRITING ELECTRONIC CONFIGURATION OF ELEMENTS - ELECTRONIC CONFIGURATION - What is the electronic configuration of Element Fluorine? THE AUFBAU’S PRINCIPLE HUND’S RULE OF MAXIMUM MULTIPLICITY PAULI’S EXCLUSION PRINCIPLE THE AUFBAU PRINCIPLE - Electrons fill orbitals starting at the lowest available energy state before filling higher states. THE ELECTRON CONFIGURATION CAN BE REPRESENTED IN TWO WAYS: - Use of the n and l quantum numbers along with the number of electrons - Box Diagram ‘ HUND’S RULE OF MAXIMUM MULTIPLICITY - States that when electrons occupy degenerate orbitals they must first occupy the empty orbitals before double occupying them. PAULI’S EXCLUSION PRINCIPLE - States that, in an atom molecule, no two electrons can have the same four electronic quantum numbers. EXAMPLE: DETERMINE THE FOUR QUANTUM NUMBERS OF THE FOLLOWING ELEMENTS: 1. N (z=7) - EC: 1s2 2s2 2p3 - OD: 1s2 ⬆ ⬇ 0 2s2 ⬆ ⬇ 0 2p3 ⬆ ⬆ -1 0 ⬆ +1 n: 2 ℓ: 1 mℓ: +1 ms: +½ GENERAL CHEMISTRY 1 2ND QUARTER WEEK 2 MORSE CODE - It is a method used in telecommunication to encode text characters as standardized sequences of two different signal duration, called dots and dashes or dits and dahs. - Named after SAMUEL MORSE - Inventor of the telegraph LEWIS STRUCTURE FROM FAMILY 1A - 8A LEWIS DOT STRUCTURE AND THE OCTET RULE WHAT IS LEWIS DOT STRUCTURE? - Electron dot structures/Lewis structure - Describe the chemical bonding of atoms in a molecule. - It is a natural formula in which dots represent electrons. GILBERT NEWTON LEWIS - He introduced Lewis Dot Structure in 1916. - Each Lewis dot symbol consists of the chemical symbol for an element surrounded by dots that represent its valence electrons. STEPS IN WRITING ELECTRON DOT SYMBOL - Write out the chemical symbol - Find the number of valence electrons - Draw the valence electrons in the following configuration The number of the valence electrons in each atom is the same as the group number of the element. This, however, is not true for HELIUM since it has only two valence electrons in the s orbital. The pattern does not also hold true for transition metals. IMPORTANCE OF LEWIS DOT STRUCTURE - - This allows you to know how it will bond and how many bonds it will form. Knowledge of LDS allows understanding of the shapes of molecules and their chemical properties. THE OCTET RULE - - - All atoms except noble gases have less than eight electrons in their valence shell Except the hydrogen atom because only two electrons complete its first shell to attain helium configuration. Those elements in unstable states combine with each other to attain a stable electronic configuration. LEWIS STRUCTURE FOR COVALENT COMPOUNDS We also use Lewis Symbols to indicate the formation of covalent bonds, which are shown in Lewis structures, drawings that describe the bonding in molecules and polyatomic ions. For example, when two chlorine atoms form a chlorine molecule, share one pair of electrons: LEWIS STRUCTURE FOR IONS Lewis symbols can be used to illustrate the formation of cations from atoms, as shown here for calcium: In the Lewis model, a single shared pair of electrons constitutes a single bond. Each Cl atom interacts with eight valence electrons total of six lone pairs and two in the single bond. Likewise, they can be used to show the formation of anions from atoms, as shown here for sulfur: - - Below shows the use of Lewis Symbols to show the transfer of electrons during the formation of ionic compounds The Lewis structure indicates that each Cl atom has three pairs of electrons that are not used in bonding (called LONE PAIRS) and one shared pair of electrons (written between atoms). A DASH (or line) is usually used to indicate a shared pair of electrons: THE COVALENT BONDING The Covalent bond can be classified into 1. Single Covalent Bond 2. Double Covalent Bond 3. Triple Covalent Bond SINGLE COVALENT BOND - - A single bond is formed when only one pair of electrons is shared between the two participating atoms. It is represented by one dash (-) For example, HCl DOUBLE COVALENT BOND - - A double bond is formed when two pairs of electrons are shared between the two participating atoms It is represented by two dashes (=) For example, Carbon dioxide TRIPLE COVALENT BOND - - A triple covalent bond is formed when three pairs of electrons are shared between the two participating atoms Three dashes represent it For example, two nitrogen GENERAL CHEMISTRY 1 2ND QUARTER WEEK 3 TRIGONAL PLANAR - GEOMETRY OF SIMPLE COMPOUNDS VSEPR THEORY (The 5 Basic Shapes) - Valence Shell Electron Pair Repulsion Model - Which can be used to predict the shapes of simple molecules. - The Lewis electron-pair approach can predict the number and types of bonds between the atoms in a substance. - It indicates which atoms have lone pairs of electrons. - This approach needs to give more information about the actual arrangement of atoms in space. - In this type of molecule, we find three molecules attached to a central atom. They are arranged in such a manner that repulsion between the electrons can be minimized (toward the corners of an equilateral triangle). The three covalent bonds in 𝐵𝐹3 repeat each other to form 120° angles in a plane. TETRAHEDRAL - The four covalent bonds in 𝐶𝐶𝑙4 arrange themselves three-dimensionally, pointing toward the corner of a tetrahedron and making bond angles of 109.5°. 𝐶𝐶𝑙4 is said MOLECULES WITH NO LONE PAIRS AROUND CENTRAL ATOMS to have a tetrahedral shape. LINEAR - - The shape of a molecule is determined by the fact that covalent bonds, which are composed of negatively charged electrons, tend to repel one another. For example, the two covalent bonds in 𝐵𝑒𝐶𝑙2 stay as far from each other as possible, ending up 180° apart from each other. The result is a linear molecule: MOLECULES WITH LONE PAIRS AROUND CENTRAL ATOMS BENT OR ANGULAR - - Similarly, 𝐻2𝑂 has two lone pairs of electrons around the central oxygen atom and two bonded electron pairs. Although the four electron pairs adopt a tetrahedral arrangement, the shape of the molecule is described by the positions of the atoms only. - The shape 𝐻2𝑂 is SUMMARY: bent with an approximate 109.5° angle. To determine the molecular geometry: STEP 1: Draw the Lewis Structure STEP 2: Count the number of bonds (a double/triple bond as one) and lone pairs around the central atom. STEP 3: Use table 1 to determine the molecular geometry. TRIGONAL PYRAMIDAL - - - Molecules with lone electrons pair around the central atom have a shape based on the position of the atoms, not the electron pairs. For example: 𝑁𝐻3 has one lone electron pair and three bonded electron pairs. These four electron pairs repel each other and adopt a tetrahedral arrangement. However, the shape of the molecule is described in terms of the positions of the atoms, not the lone electron pairs. Thus, 𝑁𝐻3 is said to have a trigonal pyramidal shape, not a tetrahedral one. POLARITY - - - A state or a condition of an atom or molecule having positive and also negative charges, especially in the case of a magnetic or an electrical pole. Refers to the physical properties of compounds such as boiling point, melting points, and their solubility. Polarity of bands mainly arises from the act between molecules and atoms with various electronegativities. ELECTRONEGATIVITY - - Chemical property that describes the power of atoms from the left-and-right-hand sides of the periodic table. An important quantity in determining the nature of bands between elements and will be considered as the main factor in chemical bonding. HOW TO DETERMINE THE POLARITY OF MOLECULES A molecule is basically said to be either a polar or a non-polar molecule. STEP 1: Start by drawing its Lewis Structure. This rule applies to all molecules except hydrocarbons and molecules with two atoms of the same element. EXAMPLES OF POLAR AND NON-POLAR MOLECULES: NON-POLAR: has a structure of its atoms lined up in a way that the orbital electrons in the outer region cancel out the electronegativity. - STEP 2: The LS will help you analyze the shape of the molecule given to you. STEP 3: Determine which of the five categories of shapes your molecule falls into linear, tetrahedral, trigonal planar, bent, or trigonal pyramid. The first three are symmetric shapes, and the last two are asymmetric shapes. STEP 4: Remember, non-polar molecules are perfectly symmetrical while polar molecules are not. This means that if the shape of the molecule given to you is a bent or trigonal pyramid, it is a polar molecule. STEP 5: Remember that asymmetry applies even if the outer atoms are the same. The arrangement of the atoms matters more. STEP 6: Now, let us dissect the symmetric molecules. All the atoms that are attached to the central atom must be the same if it is a non-polar molecule. If different kinds of atoms are attached to the central atom, the molecule is polar. - - Water is said to be a POLAR molecule due to its difference in the electronegativities between the oxygen atom and the hydrogen. Oxygen is a highly electronegative atom when compared to hydrogen. Fats, petrol, oil, and gasoline are said to be NON-POLAR molecules as they do not dissolve in water and non-polar is insoluble in water. Glucose is one more example of a POLAR molecule based on the arrangement of the oxygen and hydrogen atoms in it. GENERAL CHEMISTRY 1 2ND QUARTER WEEK 4 FUNCTIONAL GROUPS - ORGANIC: NATURAL SCIENCE TERMS: type of compound containing carbon. Organic Compounds can be categorized depending on their composition and nomenclature. FUNCTIONAL GROUP ★ Can be defined as an atom or group of atoms that are joined together in a specific manner which is responsible for the characteristics of chemical properties of organic compounds. ★ group of atoms that determines the physical and chemical properties of organic compounds. ★ The manner in which the functional groups indulge in a chemical reaction can be further modified with the help of other functional groups, and these groups can also be interconverted. A few functional groups involving carbon are illustrated in Figure 1. more functional groups ★ Some containing elements such as nitrogen and oxygen featuring different hybridizations of the carbon-nitrogen bonds. ★ The presence of functional groups in a molecule also affects the solubility and the tendency to form complexes of molecules. ★ If the functional groups of the solute and solvent interact well, the solubility increases. ★ For example, sugar and water both contain the –OH (hydroxyl) group. Sugar can be easily dissolved in water. NOMENCLATURE ❖ HYDROCARBON ❖ HALOALKANES ❖ OXYGEN-CONTAINING FUNCTIONAL GROUP DIFFERENCE BETWEEN SATURATED AND UNSATURATED CARBON COMPOUNDS KETONE: double bond with Oxygen ALCOHOL: Single bond with Hydroxide ALDEHYDE: Double bond with Oxygen; single bond with Hydrogen SATURATED COMPOUNDS UNSATURATED COMPOUNDS Are linked by only single bond between carbon atoms. Are linked by double or triple bonds between their carbon atoms. Less reactive More reactive HYDROCARBONS ➢ ALKANES ➢ ALKENES ➢ ALKYNES FUEL FORMULA Methane 𝐶𝐻4 Ethane 𝐶2𝐻6 Propane 𝐶3𝐻8 n-Butane 𝐶4𝐻10 n-Pentane 𝐶5𝐻12 Benzene 𝐶6𝐻6 n-Hexane 𝐶6𝐻14 n-Heptane 𝐶7𝐻16 n-Octane 𝐶8𝐻18 NUMBER OF C ATOMS n-Nonane 𝐶9𝐻20 meth- 1 n-Decane 𝐶10𝐻22 eth- 2 n-Undecane prop- 3 𝐶11𝐻24 but- 4 n-Dodecane 𝐶12𝐻26 pent- 5 hex- 6 hept- 7 oct- 8 non- 9 functional group that the hydrocarbon dec- 10 molecules possess. The suffix is placed ALKANES ● ● ● ● There are general rules in naming any alkane, just like how other organic compounds are named. The name of each chain, branch, or ring is based on the number of C atoms. There are three portions in naming the alkane: PREFIX + ROOT + SUFFIX The number of C atoms in the longest continuous chain in the hydrocarbon molecule is depicted by the root. ROOTS ALKANES ● The type of organic compound is indicated by the suffix used in the name. This identifies the principal after the root. For the case of alkanes, the suffix used is –ane. ● The group attached to the main chain and the number of the carbon at which it is attached is indicated by the prefix. The prefixes used to identify hydrocarbon branches are the same as the root names but have –yl as their ending. Note that each prefix is placed before the root. 𝐶𝐻3𝐶𝐻𝐶𝐻𝐶𝐻2𝐶𝐻3 I 𝐶𝐻3 I 𝐶𝐻3 2, 3-dimethylpentane CHARACTERISTICS OF ALKANES ● ● ● ● ↧ 𝐶𝐻3𝐶𝐻2𝐶𝐻2𝐶𝐻2𝐶𝐻2𝐶𝐻3 I 𝐶2𝐻5 In alkanes, the carbon atoms are bonded with a maximum number of hydrogen atoms. They have SINGLE BOND between carbon atoms. Their general formula is 𝐶𝑛𝐻2𝑛+2 The primary suffix of these hydrocarbons is ‘ane’. HOMOLOGOUS SERIES ● Is a family of organic compounds with the same general formula, similar chemical properties, and successive members differing by - 𝐶𝐻2. 3-ethylhexane WHY DO THE PHYSICAL PROPERTIES OF COMPOUNDS IN HOMOLOGOUS SERIES INCREASE? The melting and boiling points increase with increasing molecular mass. Hence, there is a gradation in physical properties. ALKENES ● ● Hydrocarbon that contains at least one carbon-to-carbon double bond (C＝C). General Formula: 𝐶𝑛𝐻2𝑛, where n is a positive integer. RULES IN NAMING ALKENES: STEP 1: Alkenes are named based on the number of carbon atoms they have. The main chain (root) of the alkene is the longest chain of carbon atoms that contain the double bond. However, the suffix –ene is used to emphasize that it is an alkene. 1 2 𝐶𝐻2 = 𝐶𝐻2 ethene 1 2 3 4 STEP 2: For alkenes with four or more carbon atoms in the chain, the main chain must contain the double bond, even if it is not the longest chain. STEP 3: The number of the first carbon in the double bond is used to give the location of the double bond. The lower number is used to indicate this carbon atom. STEP 4: If the molecule contains more than one double bond, the ending becomes diene for 2 double bonds, triene for 3 double bonds and so fourth. STEP 5: If the alkene has other substituents, then the location(s) and substituent name(s) (in alphabetical order) shall serve as the prefix to the given alkene. 8 7 6 5 4 3 7-methyl-3-octene 2 1 4-methyl-2-pentene 2-ethyl-1-hexene 5 RELATION BETWEEN THE NUMBER OF CARBON ATOMS AND HYDROGEN ATOMS IN ALKENES The ratio of the carbon atoms to the hydrogen atoms is 1:2. HALOALKANES ● Alkyl halides, functional groups which contain a bond between a carbon atom and a halogen. Prefix used to denote a halogen is ‘halo-’. Example: the compound 𝐶𝐻3𝐹 can be ● called flouromethane, and the prefix here is fluoro. F = fluoro; Cl = Chloro; B = Bromo ● ● ALKYNES ● ● ● Alkynes are aliphatic hydrocarbons that contain at least one C☰C. GENERAL FORMULA: 𝐶𝑛𝐻2𝑛−2 The alkyne is said to be internal if its triple bond is between two carbons in the middle of the carbon chain. If the triple bond is situated at the carbon atom at the end of the carbon chain, it is described as a terminal alkyne. NAMING AN ALKYNE: STEP 1: Name the longest carbon chain that contains the triple bond. STEP 2: Number the carbon chain from the end nearer the triple bond. STEP 3: Give the location and name of each substituent in alphabetical order, as the prefix for alkyne. EXAMPLE: OXYGEN-CONTAINING FUNCTIONAL GROUPS ● ● The properties of the functional groups containing a carbon-oxygen bond are entirely depend on the hybridization of the carbon-oxygen bond. The suffixes used in the nomenclature of compounds which have a functional group containing C-O bond are tabulated below along with examples. ALCOHOLS ● ● An organic compound obtained by substituting a hydroxyl group -OH for hydrogen in hydro-carbon R-OH NOMENCLATURE According to the International Union of Pure and Applied Chemistry (IUPAC), alcohols are named by changing the ending of the parent alkane name to -ol. Here are some basic IUPAC rules for naming alcohols: 1. The longest continuous chain (LCC) of carbon atoms containing the OH group is taken as the parent compound 2. —an alkane with the same number of carbon atoms. The chain is numbered from the end nearest the OH group. 3. The number that indicates the position of the OH group is prefixed to the name of the parent hydrocarbon, and the -e ending of the parent alkane is replaced by the suffix -ol. (In cyclic alcohols, the carbon atom bearing the OH group is designated C1, but the 1 is not used in the name.) Substituents are named and numbered as in alkanes. 4. If more than one OH group appears in the same molecule(polyhydroxy alcohols), suffixes such as -diol and -triol are used. In these cases, the -e ending of the parent alkane is retained. 1-butanol isopropyl alcohol EXAMPLE: 1 2 3 4 5 𝐶𝐻3𝐶𝐻2𝐶𝐻2𝐶𝐻𝐶𝐻3 I I OH ALDEHYDES & KETONES 𝐶𝐻3 4-methyl-2-pentanol 10 9 8 7 6 5 4 ● 3 2 1 6, 8-dimethyl-3-decanol 1 2 3 4 1, 5-pentanediol 5 Aldehydes and ketones are known as carbonyl compounds due to the presence of its carbonyl group (C＝O), which is a carbon atom attached to an oxygen atom with a double bond. Since these two compounds have similar functional groups, they share similarities in physical and chemical properties. However, they still have differences, particularly in chemical reactions. ALDEHYDES ● ● Aldehydes contain a carbonyl (C＝O) group, a carbon atom attached to an oxygen atom with a double bond. In an aldehyde, the carbonyl group’s carbon atom is also bonded to at least one hydrogen atom. NAMING ALDEHYDES: 1. Aldehydes take their name from their parent alkane chains. The -e is removed from the end and is replaced with -al. 2. The aldehyde funtional group is given the #1 numbering location and this number is not included in the name. 3. For the common name of aldehydes start with the common parent chain name and add the suffix -aldehyde. Substituent positions are shown with Greek letters. 4. When the -CHO functional group is attached to a ring the suffix -carbaldehyde is added, and the carbon attached to that group is C1. KETONES ● ● In a ketone, the carbonyl group is bonded to two other carbon atoms. This means that ketones have two substituents which can be an alkyl, a cycloalkyl, or an aryl group. Thus, the general formula for ketones is RC＝OR’ NAMING KETONES: 1. Ketones take their name from their parent alkane chains. The ending -e is removed and replaced with -one. 2. Unlike aldehydes, a number is needed to specify the location of the carbonyl group in the ketone. 3. The common name for ketones are simply the substituent groups listed alphabetically + ketone. 4. Some common ketones are known by their generic names. Such as the fact that propanone is commonly referred to as acetone. ● 3-methyl-2-pentanone The longest chain containing the carbonyl group has five carbons, thus, it is named as pentane. Replace the last e of the alkane name with the suffix one to indicate that it is a ketone. Indicate the position of the carbonyl group by numbering the carbon from the end nearer the carbonyl group. Afterward, name and number the substituent in the compound. Thus, the name of the compound is 3-methyl-2-pentanone. ● ● CARBOXYLIC ACIDS In the past, wherein medicines are not yet available, people chew leaves or a piece of bark from the willow tree to relieve their pain and fever. Chemists discovered that the bark of the willow tree contains salicin, which is the agent responsible for the relief of pain. However, it was also discovered that the body converts salicin to salicylic acid, a compound that contains a carboxyl group and a hydroxyl group. This compound causes irritation to the stomach lining. Pharmaceutical Based on the IUPAC system, the name of a carboxylic acid is obtained by replacing the e in the corresponding hydrocarbon name with –oic acid. ETHER ● ● companies produced an ester of salicylic acid and acetic acid called acetylsalicylic acid, also known as aspirin. Today, aspirin is used as an analgesic. In a carboxylic acid, the functional group is the carboxyl group, which is a combination of the carbonyl group and the hydroxyl group. The general formula for carboxylic acids is RCOOH, where R is any hydrocarbon chain or H. Have a general formula R-O-R’. It has an oxygen atom bonded to two carbon atoms. The R group may be the same or different. Common name of ether contain the name of the alkyl group attached to oxygen followed by the word ether. The simplest alkyl group is given first. Take a look at the example below. Both of the following are the same molecule. They are not isomers. Both are butane. ESTER ● ● Esters are formed through reactions between an acid and an alcohol with the elimination of water. Esters are named as if the alkyl chain from the alcohol is a substituent. No number is assigned to this alkyl chain. This is followed by the name of the parent chain from the carboxylic acid part of the ester with an –e remove and replaced with the ending –oate STRUCTURAL ISOMERISM Isomers are molecules that have the same molecular formula, but have a different arrangement of the atoms in space. That excludes any different arrangements which are simply due to the molecule rotating as a whole, or rotating about particular bonds. TYPES OF STRUCTURAL ISOMERISM: ❖ CHAIN ISOMERISM ➢ when molecules have the same molecular formula but have different skeletons of carbon. ❖ POSITIONAL ISOMERISM ➢ when molecules have the same molecular formula but have different bonds ❖ FUNCTIONAL ISOMERISM ➢ when molecules have the same molecular formula but separate functional groups.
