C2.1 ions & Molecules An Ion is a charged particle that results when an atom gains or loses one or more electrons Read Section 5.5 A molecule is a particle in which atoms are joined by covalent bonds (a bond that results from the sharing of outer electrons between non-metal atoms) Read section 5.10

Ionic and molecular compounds Ionic Compound (a metal & a non-metal) They transfer electrons and become charged and the charges become attracted to one another They are not physically bound together Can commonly be broken up with a solution like water because water will go between them In all ionic compounds, the positive and negative charges must be in balance Molecular Compound (2 non-metals) Their outer valence shells will overlap and they will share the electron More difficult to break up because they are sharing electrons

Kinds of Ions There are three main kinds of ions Basic ions have one charge (Li, H, Na) (Review Section 5.5) Transitional metals have two charges, and will take on a different charge depending on what it is with (Fe, W) Polyatomic ions are a group of elements acting as one and will take on one charge acting as one ion (Read Section 5.9) Example: Nitrate Ion, NO3-, Ionic Charge of -1 Example Ammonium, NH4+, +1

Naming ionic compounds Many ionic compounds are made up of two elements: a metal and a non-metal Therefore, the names of ionic compounds have two parts 1. The first part refers to the metal ion in the compound 2. The second part refers to the non-metal ion in the compound The name of the metal ion remains the same as the name of the neutral metal atom The name of the non-metal changes to “ide” Example: Metal Metal Ion Non-Metal Non-metal ion Compound magnesium Magnesium ion chlorine Chloride ion Magnesium chloride aluminum Aluminum ion oxygen Oxide ion Aluminum oxide For more information: https://www.youtube.com/watch?v=vfYnhnfdsD0

Writing chemical formulas: ionic compounds with one charge The Crisscross method Write the symbols of the elements and their ionic charges Mg2+Cl- Crisscross the numbers of the ionic charges so that they now become subscripts MgCl2 3 . The chemical formula of magnesium chloride is MgCl2

Writing chemical formulas: ionic compounds with multiple charges The same method applies, but you must pay attention to the name of the chemicals Sometimes it will be given (i.e. iron(II) bromide) Other times you will have to work from the chemical formula Example on p. 199 (considering multiple ionic charges)

Practicing writing chemical formulas In class assignment Please submit at the end of class.

Molecular compounds Read Section 5.10 Between 2 non-metals Molecular compounds both occur naturally and are produced synthetically. Some are beneficial; others are not Molecular compounds are made up of molecules. A molecule is a group of two or more atoms joined by covalent bonds A covalent bond forms when two non-metallic atoms share electrons Molecules that consist of only two atoms joined with a covalent bond are called diatomic molecules.

Elements that exist as diatomic molecules Name of element Chemical symbol Formula of molecule State at room temperature Hydrogen H H2 gas oxygen O O2 flourine F F2 bromine Br Br2 liquid iodine I I2 solid nitrogen N N2 chlorine Cl Cl2

C3.1 Naming molecular compounds (some common names) Chemical Formula Use/Occurrence Water H2O The most commonly available molecular compound on earth Ammonia NH3 Used in window cleaners and in the production of fertilizers Nitric Oxide NO An air pollutant produced in the automobile engine when gasoline in burned Hydrogen sulfide H2S An invisible gas with a distinctive “rotten egg” odor.

C3.1 Prefixes used for molecular compounds # of Atoms Sample molecular compound Mon(o)- 1 Carbon monoxide, CO Di- 2 Carbon dioxide, CO2 Tri- 3 Sulfur trioxide, SO3 Tetra- 4 Carbon tetrachloride, CCl4 Penta- 5 Phosphorus pentafluoride, PF5 The name of a molecular compounds includes prefixes to indicate how many atoms of each element are present (for example, dinitrogen pentoxide). If there is only one atom of the first element, the prefix “mono” is omitted The name of the last element ends in “ide”

C3.1 Sample problem: naming molecular compounds Name the molecular compound with chemical formula PCI3 Step 1: Write the names of both elements in the same order as in the formula. Replace the ending of the second element with “ide” Phosphorus chlorine ide Step 2: Add prefixes. Remember that the prefix “mono” is never used for the first element phosphorus tri chloride The compound with chemical formula PCI3 is called phosphorus trichloride

Writing chemical formulas of molecular compounds Given its name, writing the formua of a molecular compound is relatively simple. The prefixes in the name become the subscripts in the formula. For example, the molecular compound called sulfur dioxide has the chemical formula SO2