Results for "octet rule"

Ch 2 Chemical Compounds and Bondings Chemical bond: force of attraction between 2 atoms or 2 ions. There are 2 main types of chemical bonds: 1. Ionic bond: a bond between a metallic atom (metal) and a non-metallic atom (non-metal) in which there is a complete transfer of electrons from the metal to the non-metal. The compound which is formed is called an ionic compound. Ex.: NaCl , MgCl2, Al2O3 To write the formula of an ionic compound we use the criss-cross method (we down cross multiply the charges without the sign, only the numbers of the charges) Remark: if the charges are the same then they cancel each other in the formula so there will be one atom of the metal and one atom of the non-metal in the compound. Exercise: Write the formula of the compound which is formed between the following elements, and name each compound. a) Rb and S: b) Ca and Se: c) Al and Br: d) Na and N: - Draw a Bohr diagram to show the transfer of electrons (loss / gain) in an ionic compound. Example: Na2O (sodium oxide) Remark: The ionic bond is also described as an electrostatic force of attraction between a positive ion and a negative ion (eg: Na+ Cl- ). 2. Covalent bond: a bond between a non-metal and another non-metal in which there is a sharing of electrons between the non-metallic atoms. The compound that is formed is called a covalent or molecular compound. Molecule: 2 or more atoms (non-metallic) bonded together; the atoms can be of the same element such as O2 or of different elements such as HCl, CH4, H2O,….. We show the sharing of electrons between non-metallic atoms by using the Lewis diagram. In addition we can make intersecting circles for the atoms to show the sharing. Reminder: Lewis diagram of an atom shows only the valence electrons of that atom. Most of the atoms follow the octet rule (there are very few exceptions), that is each atom will have eight electrons in the valence shell (same as noble gases) except hydrogen will have 2 electrons after sharing (same as helium). Remark: 2 electrons that are not bonded to any other atom is called a lone pair (non-bonding pair) of electrons. Exercise: Draw lewis diagrams to show the sharing of electrons in each of the following compounds: 1. NF3 2. CH4 3. CO2 4. CCl4 5. CH2O Remark:In drawing Lewis structure, we show the bonds between the atoms and we also show all lone pairs (if present) on any atom. - Naming molecular compounds: 1: mono 2: di 3: tri 4: tetra 5: penta 6: hexa 7: hepta 8: octa 9: nona 10:deca Example: PCl5 : phosphorus pentachloride Remark: If the first element contains only one atom we don’t write mono before it; If the second element contains only one atom we have to write mono before it. Ex.: NO : nitrogen monoxide CO: carbon monoxide Exercise: Fill in the table below Name Chemical Formula diphosphorus pentoxide SO3 CO Aluminum sulfide Al2S3 SF6 Calcium oxide Lithium nitride Li3N Remark: If the compound contains a transition metal, then we have to mention the type of charge of the transition metal by inserting a roman numeral in brackets (I, II, III, IV ….) after the symbol of the transition metal. Example: Name the following compounds: - FeCl2 : Iron (II) chloride - Cu(NO3)2 : Copper (II) nitrate Remark: There are few transition metals that have only one type of charge such as zinc, nickel, and silver; in this case no roman numeral is required. Zinc : Zn+2 Silver: Ag+ Nickel: Ni+2 - ZnSO4 : zinc sulfate - AgNO3 : silver nitrate - CuSO4 : copper (II) sulfate - Co(NO3)3 : cobalt (III) nitrate Exercise: Write the formula of the following compounds. Calcium phosphate: Iron(III) hydroxide: Sodium hydroxide: Manganese(II) hydroxide: Barium sulfate: Zinc carbonate: Ammonium nitrate: Remark: We must enclose the polyatomic ion in brackets if the number after it is more than 1. Note: If the polyatomic ion that ends with the prefix –ate decreases by one oxygen atom then the prefix changes to -ite. If the prefix ending with – ite decreases by one oxygen atom then we precede the prefix by hypo, whereas if the prefix ending with – ate increases by one oxygen atom then we precede the prefix by per. Example: ClO3- is called chlorate; if we reduce one oxygen atom then the ion becomes ClO2- and is called chlorite, however if we increase by one oxygen atom then the ion becomes ClO4- and is called perchlorate; and if the chlorite is reduced by one oxygen atom then the ion becomes ClO- and is called hypochlorite. Exercise: Name the following compounds: K2SO3 : NaNO2 : Mg(ClO4)2 : LiBrO2 : - Comparison Table between ionic and covalent (molecular) compounds: property Ionic Compounds Covalent Compounds State (at room temperature) solids Solids, liquids or gases Melting point and boiling point Very high Usually low Involvement of electrons Loss and gain (transfer) of electrons Sharing of electrons Electric conductivity When dissolved in water (in solution) , electric conductivity is high

resonance and exceptions to the octet rule

HOMEOSTASIS Maintaining a stable internal environment respond to stimuli Reacting to changes in the environment reproduce and develop Creating new organisms and growing adapt and evolve Changing over time to better suit the environment INDUCTIVE REASONING Making generalizations based on specific observations DEDUCTIVE REASONING Making specific predictions based on general principles Matter Anything that has mass and takes up space elements Substances that cannot be broken down into simpler substances protons Positively charged particles in the nucleus neutrons Neutral particles in the nucleus electrons Negatively charged particles orbiting the nucleus Atomic Number Number of protons in an atom Isotopes Atoms of the same element with different numbers of neutrons Octet Rule Atoms tend to gain, lose, or share electrons to achieve a full outer shell of 8 electrons molecule Two or more atoms held together by chemical bonds compound A substance consisting of two or more different elements IONIC BONDS Bonds formed by the transfer of electrons COVALENT BONDS Bonds formed by the sharing of electrons reactants Starting materials in a chemical reaction products Ending materials in a chemical reaction WATER solvent Dissolves many substances WATER cohesion & adhesion Water molecules stick to each other and other surfaces WATER high surface tension Water's surface resists being broken WATER high heat capacity Water can absorb a lot of heat without changing temperature WATER heat of vaporization Water requires a lot of energy to evaporate WATER varying density Ice is less dense than liquid water acidic solutions Solutions with a pH below 7 basic solutions Solutions with a pH above 7 pH scale Measures the acidity or basicity of a solution buffers Substances that resist changes in pH Organic Molecules Molecules containing carbon carbon The backbone of organic molecules functional groups Chemical groups attached to carbon that give molecules specific properties Macromolecules Large molecules made up of smaller subunits monomers The individual subunits of a polymer polymers Long chains of monomers Dehydration Synthesis Reaction Joins monomers by removing water Hydrolysis Reaction Breaks polymers by adding water Role of Enzymes Speed up chemical reactions Carbohydrates monosaccharides glucose Simple sugars Carbohydrates disaccharides glycosidic bonds Two monosaccharides joined together Carbohydrates polysaccharides starch glycogen cellulose Many monosaccharides joined together LIPIDS Glycerol & Fatty Acids saturated Fatty acids with no double bonds LIPIDS Glycerol & Fatty Acids unsaturated Fatty acids with double bonds PROTEINS Enzymes Proteins that catalyze chemical reactions PROTEINS amino acids peptide bonds The monomers of proteins, joined together PROTEINS protein structure primary The sequence of amino acids PROTEINS protein structure secondary Local folding patterns (e.g., alpha-helices and beta-sheets) PROTEINS protein structure tertiary The overall 3D shape of a single polypeptide PROTEINS protein structure quaternary The arrangement of multiple polypeptides in a protein conformation The 3D shape of a protein denaturation The unfolding of a protein DNA Deoxyribonucleic acid, the genetic material RNA Ribonucleic acid, involved in protein synthesis ATP Adenosine triphosphate, the energy currency of the cell

CHEM 1211 Section 4.8 (Exceptions to the Octet Rule)

bonding: lewis structures, the octet rule, and exceptions

1.3 Ions and the Octet Rule

Atomic Bonding and Octet Rule

Octet Rule Exceptions

chem - unit 2 octet rule exceptions

Physical Science - Chemical Bonding: The Octet Rule, Ionic Bonds, Covalent Bonds

Chapter 9: Molecular Geometry and Bonding Theories

chemistry- octet rule exceptions

Chapter 8: Basic Concepts of Chemical Bonding

Pauli Principle, Hund's Rule, Octet Rule & Aufbau Principle

FLC CHEM 305: Electronegativity, Diatomics, Ions, the Octet Rule, Avogadro's Number, and Moles

Octet Rule

Lecture 12: Exceptions to Octet Rule, Formal Charge, Resonance

Ionic, Molecular, Acids, Element, and Octet Rule

Understanding the Octet Rule and Ionic Bonds

ionic vs covalent bonds