Lecture - Chemistry Review PDF

Lecture Volume – amount of space a substance fills Viscosity – the thickness / resistance of a *Physical Property and Chemical Property...

Lecture Volume – amount of space a substance fills Viscosity – the thickness / resistance of a *Physical Property and Chemical Property fluid to flow; ex. Molasses has a high Physical Properties – describes a viscosity compared to water characteristic of a substance that can be observed or Density – the amount of mass in a given measured volume of a substance; ex. The density of pure water is 1g/mL Qualitative Observation – can be observed using the senses and described with words CHEMICAL CHANGE Quantitative Observation – are measured Combustibility – ability of a substance to and recorded using numbers (have units) react with oxygen and release heat and light energy Chemical Properties – describes the ability Reaction with Acid – ability of a substance of a substance to change into a new substance/s to react with an acid and produce gas - can only be observed when a Corrosion – ability of metal to react with air chemical change occurs to produce metal oxides *Physical and Chemical change *Types of Mixture PHYSICAL CHANGE Pure Substances – a substance that has constant composition and properties (contains only Color and Luster – the light a substance one kind of particle) reflects gives an object color and shine (luster) Element – a pure substance that Malleability – a substance that can be cannot be broken down by ordinary pounded or rolled into sheets is said to be means; e.g.) any example from “malleable”; ex. Aluminum foil, gold, tin periodic table Ductility – any solid that can be stretched Compounds – a pure substance that into a long wire is called “ductile”; ex. contains two or more different Copper elements in a fixed proportion. The State – solid, liquid, or gas at room elements are chemically bonded; e.g.) temperature H2O, NaCl, C12H22O11 Texture – how the surface of a substance Mixture – a substance that contains two or feels to the touch more different pure substances that are NOT Odor – how a substance smells (e.g. chemically combined odorless, burnt, flowery, putrid, spicy) Taste – e.g. sweet, salty, bitter, sour, spicy - components can be separated by Clarity – e.g. clear, transparent, translucent physical means (e.g. filtration, evaporation, Crystal Form – solid mineral structure with distillation) a regular pattern of 3D shapes (e.g. cubic Homogeneous Solution – a mixture (salt) that has “uniform” composition – i.e. Melting & Boiling Point – MP – solid to One phase. The components within liquid; BP – liquid to gas the solution are not identifiable with Solubility – ability to dissolve in a solvent the eye. (water) o Solute – the particle that is Hardness – a substance’s ability to resist present in smaller being scratched; scale 1 to 10 Mass – amount of matter in a substance (g)  proportions. The dissolved largely towards of the entertainment particle. of the army Xerxes on his return to o Solvent – the particle in larger Asia. proportion. The substance in ❖ Democritus (460 BC – 370 BC) which the solute is dissolved. ▪ Proposed an Atomic Theory which o Alloy – a homogeneous states that all atoms are… mixture of one or more ▪ Small metals. ▪ Hard Heterogeneous Mixture – a ▪ Indivisible and indestructible substance in which the different ▪ Made of a single material components are identifiable. Has two ❖ John Dalton (1766 – 1844) or more phases. ▪ In 1803, proposed an Atomic Theory o Mechanical mixture - a which states: substance in which the ▪ All substance are made of atoms; particles are not uniformly atoms are small particles that cannot scattered. be created, divided, or destroyed. o Suspension – suspended ▪ Atoms of the same element are particles can be seen with the exactly alike unaided eye. If left ▪ Atoms join with other atoms to make undisturbed, gravity will new substances cause the particles to separate. ▪ The “Billiard Ball” Model o Emulsion – a suspension of ▪ Proposed by John Dalton in 1804 liquids where separation of ▪ This theory proposed that matter was particles is prevented through composed of small, spherical the use of an emulsifying particles agent. ▪ But evidence was later gathered that o Colloid – suspended particles matter was composed of even smaller cannot be seen with the bits unaided eye. Gravity will not ❖ Aristotle (384 BC – 322 BC) cause them to separate (they ▪ Was born on June 19 384BC in appear to be homogeneous) Stagira Greece. He died in March 7 o Tyndall Effect – the 322BC Chalcis Greece. scattering of a beam of light ▪ Vehemently opposed the atomic caused by particles in a theory develop by Democritus, he colloid. Allows homogeneous believed that instead of being made solutions and colloids to be tiny particles (atom) that they were all distinguished. fundamentally air, fire, water, and earth. *Atomic theory ❖ Leucippus Who discovered ATOM? ▪ Was born in Miletus Turkey and died in 370BC Democritus – was the first ▪ The indivisibility of an atom was discovered atom. proved to wrong: an atom can be Was born in Abdera Thrace around further subdivided into protons, 460 BCE and he died in Greece, he neutron, and electrons. died in age of 90, the father of ▪ However atoms is the smallest Democritus is from a noble family particles that takes parts the chemical and of a great wealth and contribute reaction.  MOLECULE - is the smallest unit of a substance. - ANGSTROM – a unit of a length equal to 100 million of a centimeter 10-10 meter, used mainly express wavelength and interatomic distance. ❖ J.J. Thomson (1856 – 1940) ▪ Proved that an atom can be divided into smaller parts ▪ Niels Bohr proposed that electrons ▪ Discovered electrons revolve around the central positive ▪ In 1897, proposed the Plum Pudding nucleus (like planets in the solar Model system) ▪ Atoms mostly consist of positively charged “pudding” with negatively charged “plums” (electrons) located throughout ▪ Thomson: “Plum Pudding” or “Chocolate Chip Cookie” Model ▪ Using available data on the atom, J.J. ❖ Erwin Schrodinger (1887 – 1961) Thomson came up with the idea of ▪ In 1962, explained that the exact having charges embedded with location of an electron cannot be Dalton’s Billiard Balls stated; ▪ Also used cathode ray experiment to ▪ It is more accurate to view the discover the existence of the electron electrons in regions called electron clouds ❖ Ernest Rutherford (1871 – 1937) ▪ In 1909, suggested the following characteristics of the atom: ▪ It consists of a small core, or nucleus ▪ This nucleus is made up of particles called protons ▪ Most of the atom is actually empty space Quantum Mechanical Model ❖ Niels Bohr (1885 – 1962) - This model sees the electrons not as ▪ The Bohr Model individual particles, but as behaving like ▪ Suggests that electrons travel around a cloud – the electron can be “anywhere” the nucleus in orbits in a certain energy level ▪ First to discover that electrons travel in separate orbits around the nucleus.  * Periodic law ❖ Mendeleev: Developing a Periodic Table ▪ In 1869 a Russian chemist, inventor and teacher names Dimitri Mendeleev. formulated the Periodic Law. He used it to correct the properties of some already discovered elements and also to predict the properties of elements yet to be discovered. ▪ Mendeleev studied the physical ❖ James Chadwick (1891 – 1974) properties such as density, color, ▪ Realized that the atomic mass of most melting point and atomic mass of elements was double the number of each element. protons ▪ Mendeleev also studied chemical ▪ Discovered of the neutron in 1932 properties such as how each element reacted with other elements. ▪ He arranged the elements in a list using their atomic masses. ▪ He noticed that the properties of the elements seemed to repeat in a pattern. ▪ When Mendeleev placed his list of elements into a table, he arranged them in rows of increasing atomic mass. Elements with similar properties were grouped in the same columns ❖ Periodic Table: Patterns in Properties ▪ Mendeleev noticed that melting point is one property that shows a repeating pattern. ▪ Boiling point and reactivity also follow a periodic pattern. ❖ Periodic Table: Predicting Properties ❖ Periodic Table: Organization ▪ When Mendeleev arranged the ▪ The table is organized into columns, elements by increasing atomic mass, rows, and blocks, which are based on there were large gaps between some certain patterns of properties. elements. ❖ Periodic Table: Element Key ▪ He predicted that scientists would ▪ The element key shows an element’s discover elements that would fit into chemical symbol, atomic number, and these spaces. atomic mass. ▪ He also predicted that the properties ▪ The key also contains a symbol that of these elements would be similar to shows the state of matter at room the known elements in the same temperature. column. ▪ He was right! Both predictions turned out to be true! ▪ Mendeleev believed that the atomic masses of certain elements must be invalid because the elements appeared in the wrong place on the periodic table. ▪ He placed elements whose properties resembled each other’s closer ❖ Periodic Table: Groups together in the table. ▪ A group is a column on the periodic ▪ In the early 1900’s Henry Moseley table. solved the problem! ▪ Elements in the same group have ▪ When Moseley listed the elements similar chemical properties and react according to atomic number, columns with other elements in similar ways. contained elements with similar ▪ There are patterns in the physical properties, such as copper, silver, and properties of a group such as density, gold. melting point, and boiling point. ❖ Periodic Table: New Elements ▪ The groups are numbered 1-18. ▪ Even today, new elements are created ❖ Periodic Table: Periods in laboratories, named, and added to ▪ The rows on the periodic table are the present-day periodic table. called periods. ▪ These elements are all synthetic and ▪ The atomic number of each element do not occur naturally on Earth. increases by one as you read from left ▪ Scientists can use the periodic table to to right across each period. predict the properties of new elements ▪ The physical and chemical properties they create. also change as you move left to right across a period. ❖ Metals: Properties ▪ Almost 3/4 of the elements on the periodic table are metals. ▪ Metals are on the left side and in the middle of the periodic table.  ▪Some can occur in nature as free elements, meaning that it is pure form, it is not within a compound. ▪ Because of their high densities, strength, and resistance to corrosion, transition elements make good ❖ Metals: Group 1 - Alkali Metals building materials. ▪ The elements in group 1 are called ▪ Name one everyday use of a alkali metals. transitional element. ▪ Alkali metals have similar chemical ▪ Two rows of transition elements—the properties. lanthanide and actinide series—were ▪ They react quickly with other removed from the main part of the elements, such as oxygen. table so that periods 6 and 7 were not ▪ Because of this, in nature they only longer than the other periods. occur in compounds. ▪ Some lanthanide and actinide series ▪ Alkali metals have similar physical elements have valuable properties. properties. They have a silvery ▪ Lanthanide series elements are used appearance. to make strong magnets. ▪ They are soft enough to be cut with a ❖ Metals: Patterns in Properties knife. ▪ Metallic properties include luster, ▪ They have the lowest densities of all malleability, and electrical metals. conductivity. ❖ Metals: Group 2 - Alkaline Earth Metals ❖ Nonmetals ▪ The elements in group 2 are called ▪ More than 96 percent of the mass of alkaline earth metals. the human body comes from four ▪ Alkaline earth metals also react nonmetals–oxygen, carbon, quickly with other elements, but not hydrogen, and nitrogen. Nonmetals as quickly as alkali metals. ▪ Nonmetals are elements that have no ▪ Pure alkaline earth metals do not metallic properties. occur naturally. Instead they combine ▪ The four elements that make up most with other elements to form of the human body, along with compounds. phosphorus and sulfur, are the six ❖ Metals: Group 3-12 - Transition Elements elements in proteins, fats, nucleic ▪ Groups 3-12 are called transition acids, and other large molecules in elements. your body and in all other living ▪ Transition elements are in a block at things. the center and two rows at the bottom Metals Nonmetals of the periodic table. solid at room many are gases at room ▪ Many colorful materials contain small temperature (except temperature amounts of transition elements. mercury) ▪ All transition elements are metals have luster those that are solid have with higher melting points, greater a dull surface, therefore strength, and higher densities than the no luster alkali metals and the alkaline earth good conductors of poor conductors of metals. electricity and thermal electricity and thermal ▪ Transition elements also react less energy energy, therefore good quickly with oxygen. insulators ductile, malleable ❖ Nonmetals: Properties ❖ Nonmetals: Hydrogen ▪ Phosphorus and carbon are dull, ▪ Hydrogen is most often classified as a brittle solids that do not conduct nonmetal because it has many thermal energy or electricity. properties like those of nonmetals. ▪ With the exception of hydrogen, ▪ However, hydrogen also has some nonmetals are located on the right properties similar to those of the side of the periodic table. group 1 alkali metals. ❖ Nonmetals: Group 14-16 ▪ Under conditions on Earth, hydrogen ▪ Groups 14-16 contain metals, usually behaves as a nonmetal. nonmetals, and metalloids. ❖ Metalloids: Properties ▪ The chemical properties of the ▪ Between the metals and the elements in each group are similar. nonmetals on the periodic table are ▪ The physical properties are quite the metalloids. different. ▪ A metalloid is an element that has ❖ Nonmetals: Group 17: The Halogens physical and chemical properties of ▪ The term halogen refers to an element both metals and nonmetals. that can react with a metal and form a ▪ Silicon is the most abundant salt. metalloid in the universe. ▪ For example chlorine gas reacts with ▪ Remember that metals are good solid sodium and forms sodium conductors of electricity and thermal chloride (NaCl). energy. Nonmetals are poor ▪ Halogens react so readily that they conductors. can only occur naturally in ▪ A property of metalloids is the ability compounds. They do not exist as free to act as a semiconductor. elements. ▪ A semiconductor conducts electricity ▪ They even form compounds with at high temperatures, but not at low other nonmetals, such as carbon. temperatures. ▪ Halogens are less reactive as you ▪ At high temperatures metalloids act move down the group. like metals and conduct electricity. ❖ Nonmetals: Group 18: The Noble Gases ▪ At lower temperatures metalloids act ▪ The elements in group 18 are known like nonmetals and stop electricity as the noble gases. from flowing. ▪ Unlike the halogens, the only way ▪ This property is useful in electronic elements in this group react with other devices such as computers, tv’s and elements is under special conditions solar cells. in a laboratory. ▪ An element’s position on the periodic ▪ Of all the elements, hydrogen has the table tells you a lot about the element. smallest atomic mass and is the most ▪ Understanding the properties of common element in the universe. elements can help you decide which ▪ These elements were not discovered element to use in a given situation. when Mendeleev constructed his periodic table because they do not form compounds naturally. ▪ Once they were discovered they fit into a group at the far right of the table. * Lewis Structure Polar Covalent Bond A Polar Covalent Bond is unequal AIM: How to write Lewis Dot Structures sharing of electrons between two (Electron Dot Structures) atoms (H-Cl) Valence Electrons In a polar covalent bond, one atom typically has a negative charge, and Are the electrons in the highest occupied the other atom has a positive charge energy level of an atom Nonpolar Covalent Bond You can tell the number of valence electrons A Nonpolar Covalent Bond is an equal from the group number sharing of electrons between two atoms Octet Rule (Cl-Cl, N-N, O-O) Says that atoms like to have full outer shells of only eight electrons. Atoms will lose or gain valence electrons to make their outer shells full with eight electrons, and they do this by bonding with other atoms. Lewis Dot Structure (Electron Dot Structure) is a quick and easy diagram that shows the valence electrons in an element. In a Lewis structure, the nucleus of the element is represented by its symbol. The valence electrons are represented by dots placed around the symbol in pairs Classification of Bonds Rule #1. No side can have more than You can determine the type of bond between two dots because orbital can only hold two atoms by calculating the difference in two electrons. electronegativity values between the elements. Rule #2. When filling the sides of the element symbol each side gets one dot The bigger the electronegativity difference before doubling up. Exceptions are the more polar the bond. hydrogen and helium. * Polarity Polarity - In chemistry, polarity is a separation of electric charge leading to a molecule or its chemical groups having an electric dipole Examples moment, with a negatively charged end and a positively charged end. Polar and Nonpolar Bonds There are two types of covalent bonds o Nonpolar Covalent Bonds (equal share of electrons) o Polar Covalent Bonds (unequal share of electrons) How to show a bond is polar Dipole Isn’t a whole charge just a partial charge When there is unequal sharing of + means a partially positive (less electrons a dipole exists electronegative) Dipole is a molecule that has two poles or − means a partially negative (more regions with opposite charges electronegative) The Cl pulls harder on the electrons A dipole is represented by a dipole arrow The electrons spend more time near the Cl pointing towards the more negative end Polar Molecules Molecules with a positive and a negative end Requires two things to be true The molecule must contain polar bonds The properties of a substance depend in part on This can be determined from it’s polarity differences in electronegativity. Polar Compounds Asymmetric molecule. If a molecule has polar bonds (and Stronger intramolecular forces. there is no symmetry to cancel out + and – charges), the molecule is polar. Form ions when dissolved in water. Higher melting and boiling points. Conduct electricity in water. Non-polar Compounds Weak intramolecular forces. Symmetrical Molecules Because of symmetry, molecules that Do not form ions. have polar bonds are overall a nonpolar molecules (+ and – charges Lower melting and boiling points. cancel out or balance out) Do not conduct electricity. In a polar bond, one atom is more electronegative than the other. In a nonpolar bond, both atoms have similar electronegativities. An asymmetric molecule with polar bonds is a polar molecule. An asymmetric molecule with nonpolar bonds is a nonpolar molecule. A symmetric molecule, regardless of the polarity of the bonds, is always a nonpolar molecule. * VSEPR theory (Valence Shell Electron Pair Repulsion) VSEPR theory was suggested by Sidwick and Powel (1940) It was developed by Gillespe and Nyholm in 1957. Based on that in a polyatomic molecule the direction bonds around the central atom depends on the total number of Bonding & Non-bonding electron pairs in its valance shell. VSEPR Theory The shape of the molecule is determined by repulsions between all of the electron present in the valance shell. Electron pairs in the valence shell of the central atom repel each other and align themselves to minimize this repulsion Lone pair electrons takes up more space around the central atom than a bond pair. Lone pair attracted to one nucleus, but bond pair is shared by two nuclei. The minimum repulsions to the state minimum energy and maximum stability of the molecule. Repulsion Strengths Lone pair – Lone pair > Lone pair – Bond pair > bond pair – Bond pair Triple bond > double bond > single bond Presence of lone pairs on the central atoms causes slight distortion of the bond angles from the ideal shape. The magnitude of repulsions between bonding pairs of electrons depends on the electronegativity difference between the central atom & the other atoms.