PS+4+-Chemical+Reactions+and+Compounds


 * ====Standard PS-4:==== || ====[|The student will demonstrate an understanding of chemical reactions and the classifications, structures, and properties of chemical compounds.]==== ||
 * Indicators:**
 * || PS-4.1 || [|Explain the role of bonding in achieving chemical stability.] ||
 * || PS-4.2 || [|Explain how the process of covalent bonding provides chemical stability through the sharing of electrons.] ||
 * || PS-4.3 || [|Illustrate the fact that ions attract ions of opposite charge from all directions and form crystal lattices.] ||
 * || PS-4.4 || [|Classify compounds as crystalline (containing ionic bonds) or molecular (containing covalent bonds) based on whether their outer electrons are transferred or shared.] ||
 * || PS-4.5 || [|Predict the ratio by which the representative elements combine to form binary ionic compounds, and represent that ratio in a chemical formula.] ||
 * || PS-4.6 || [|Distinguish between chemical changes (including the formation of gas or reactivity with acids) and physical changes (including changes in size, shape, color, and/or phase).] ||
 * || PS-4.7 || [|Summarize characteristics of balanced chemical equations (including conservation of mass and changes in energy in the form of heat-that is, exothermic or endothermic reactions).] ||
 * || PS-4.8 || [|Summarize evidence (including the evolution of gas; the formation of a precipitate; and/or changes in temperature, color, and/or odor) that a chemical reaction has occurred.] ||
 * || PS-4.9 || [|Apply a procedure to balance equations for a simple synthesis or decomposition reaction.] ||
 * || PS-4.10 || [|Recognize simple chemical equations (including single replacement and double replacement) as being balanced or not balanced.] ||
 * || PS-4.11 || [|Explain the effects of temperature, concentration, surface area, and the presence of a catalyst on reaction rates.] ||
 * || PS-4.11 || [|Explain the effects of temperature, concentration, surface area, and the presence of a catalyst on reaction rates.] ||

• Atoms bond chemically to become more stable •  To become more stable, atoms want to have either two or eight valence electrons. •  Group 1 and Group 2 metals tend to transfer electrons to Group 16 or Group 17 nonmetals to form ionic bonds. •  Metals tend to lose electrons to achieve a stable noble gas structure •  Nonmetals tend to gain electrons to achieve a stable noble gas structure •  When a metal loses an electron and a nonmetal gains that electron they bond and become stable through ionic bonding •  Nonmetals bond with each other by sharing electrons to become stable through covalent bonding

• In a covalent bond, electrons are shared like co-captains share the role of captain of the team • Nonmetals other than the noble gases have less than the number of electrons that they need in order to be stable. • Nonmetals tend to gain electrons to become more stable • Other than gain electrons, nonmetals can share electrons in order to become more stable • For example: group 17 atoms can bond with other group 17 atoms by sharing one electron from each atom. By sharing electrons, each atom becomes stable because it has a full valence shell • The atoms would form one covalent bond consisting of two shared electrons • The molecule formed is more stable than the individual atoms • An electron dot diagram is one way to represent an atom. • In an electron dot diagram, the symbol of the atom is surrounded its valence electrons • Paired electrons are groups of two electrons on the top, bottom, left or right of the symbol of the atom. • Unpaired electrons are single electrons on the top, bottom, left or right of the symbol of the atom

This diagram shows how you can use electron dot diagrams to show how atoms bond to form compounds

Ionic Bonds §  A **__chemical formula__** is composed of symbols and subscripts indicating the number of atoms of an element in a compound. §  An ionic compound is held together by the **__ionic bond__** – the force of attraction between opposite charges of the ions. Ionic bond – electron from Na is transferred to Cl, this causes a __charge imbalance__ in each atom. The Na becomes (__Na+__) and the Cl becomes (__Cl-__), charged particles or __ions__. Forms NaCl • A chemical formula is like a ‘word’ that stands for one type of chemical compound. • The ‘word’ is made up of atoms represented by symbols (the ‘letters’ that make up the word) • Examples: – The formula for water is H2O – The formula for table sugar is C12H22O11 – The formula for aspirin is C9H8O4 • The little numbers are called __subscripts__ and tell you how many atoms you have of each element. • To balance chemical formulas you need to know oxidation numbers. •  An __oxidation number__ is the charge that results when the atom __loses or gains__ electrons to become more stable. – //Don’t forget:// An atom is more stable when it has __8__ valence electrons (or if it has __2__ valence electrons if it has two total electrons) – More simply, an oxidation number is the __charge__ of the __ion__ that forms. • Oxidation Numbers/Charges of Atoms Form __1+__ ions Form __2+__ ions Form __2-__ ions Form __1-__ ions • __Ion__- atom with a net charge because it has a different number of protons and electrons (it has either gained or lost electrons) • __Cation__- positively charged ion • __Anion__- negatively charged ion
 * Group 1 **
 * Group 2 **
 * Group 16 **
 * Group 17 **