Chemical Bonds J. E. Odom 2014

Compounds and Chemical Formulas Compound – Two or more elements chemically combined Chemical Formula – Chemical “short hand” – Shows what ELEMENTS a compound contains – Shows HOW MANY ATOMS of each element H2OH2O C 6 H 12 O 6 2 atoms of Hydrogen 1 atom of Oxygen 6 atoms of Carbon 12 atom of Hydrogen 6 atoms of Oxygen

Common Chemical Compounds Can you tell what elements are present and HOW MANY atoms of each element are present in each compound?

Why do elements form compounds? – All atoms want a full outer electron shell – FULL Outer Shell = stable atom (less reactive) EXAMPLES: H and He need 2 electrons to become Full/stable Groups 1 – 18 need at least 8 electrons to be full/stable

VALENCE ELECTRONS = Electrons in the outermost shell of an atom

Chemical Bonds ATOMS WILL FORM BONDS in order to fill the outer electron shell…to become more stable Chemical Bond = Attraction between atoms when electrons are gained, lost or shared 2 types of bonds Ionic Covalent

What happens when an atom Gains or Loses an electron just to be stable? The atoms become IONS (Charged particles)

ATOM Loses electron (-) BECOMES MORE POSITIVE ATOM Gains electron (-) BECOMES MORE NEGATIVE The + or – Charge of the ion is equal to the NUMBER of electrons lost or gained

PRACTICE For each of the following compounds, LIST the elements present AND the number of atoms of each element 1) 2) 3) 4) 5) 6) 7) 8) 9) 10) For each of the following elements, state the VALENCE electrons. 11)Nitrogen (N) 12)Hydrogen (H) 13)Potassium (K) 14)Calcium (Ca) 15)Carbon (C) 16)Argon (Ar) 17)Aluminum (Al) 18)Silicon (Si) 19)Lithium (Li) 20)Beryllium (Be) In your notebook, write the problem and the solution For each of the following atoms, write the NEW ION that is formed AND its charge 21)Calcium loses 2 e- 22)Sodium loses 1 e- 23)Chlorine gains 1 e- 24)Lithium loses 1 e- 25)Magnesium loses 2 e- 26)Bromine gains 1 e- 27)Aluminum loses 3 e- 28)Sulfur gains 2 e- 29)Iron loses 2 e- 30)Potassium gains 3 e-

Lewis Dot Structure Structure that shows the valence electrons for a given atom; helps predict how one atom might combine with another atom to form a compound.

PRACTICE ELEMENT Chemical Symbol Total number of Electrons Valence Electrons Dot Diagram PotassiumK NitrogenN CarbonC BerylliumBe NeonNe SulfurS NOW…Try to predict the chemical formulas Elements Dot Diagram for EACH Element Dot Diagram for Compound Chemical Formula Na and F Br and Br Mg and O Complete the following tables in your notebook

Day 2 Ionic & Covalent Bonds

IONIC BONDS – Force of attraction between opposite charged ions – Form between METALS & Non-metals

Ionic Compounds IONS ARE FORMED +Cation – Metals – Lose electrons – Carry a (+) oxidation number -Anion – Nonmetals – Gain electrons – Carry a (-) oxidation number

Oxidation Number Number of electrons gained, lost or shared to become stable (NEGATIVE means that electrons will be gained; POSITIVE means that electrons will be given away)

THIS IS NOT VALENCE RECOGNIZE THE DIFFERENCE??? Using RED pen/pencil Write the Oxidation Number for each group on the chart.

Covalent Bonds – Attraction between atoms when they share electrons – Sharing occurs between 2 or more NON-METALS – Can have equal or unequal sharing – Equal sharing = no charge or neutral compound also called Non-Polar – Unequal sharing = POLAR MOLECULE (EX: Water)

Covalent Bonds

PRACTICE Before moving forward students must understand… 1.What are Valence Electrons 2.How to complete an Electron dot diagram for an element 3.How to create an electron dot diagram for a compound 4.Difference between Ionic and Covalent bonds 5.How to find the oxidation number for a given element

STEPS TO Create compounds from combinations of elements: 1)Are the elements METALS or NON-METALS (This determines whether they will form ionic or covalent bonds) 2)What is the Valence 3)What will the Element need to fill its outermost shell? 4)Will you need additional atoms of the element to satisfy the outermost shell requirements; if so, how many? 5)Draw the Electron Dot Diagram showing either transferred electrons or shared electrons. 6)What is the chemical formula for the compound?

Writing & Naming Compounds

BINARY compound is a compound composed of two elements REMEMBER: Oxidation number tells us how many electrons an atom has Lost, Gained, or shared to become stable. Ionic Compounds: elements themselves become ions Ions have a charge, but the net charge of the compound is ZERO.

Binary Ionic Compounds Composed of only two elements IONIC: Metal + Non-metal

Shortcut to Writing Binary Ionic Compounds 1.Write oxidation numbers above symbols 2.Criss-cross oxidation numbers writing them as subscripts (small numbers at the bottom right of the element) 3.The metal is ALWAYS written first 4.Will always be between (+) and (-) ions

PRACTICE: MetalCation(+)NonMetalAnion (-) Compound Formula SodiumNa +1 OxygenO -2 Na 2 O AluminumSulfur Magnesium Phosphoru s PotassiumSelenium

Naming Binary Ionic Compounds 1.Write the name of the metal/cation first 2.Drop the end of the nonmetal 3.Add “ide” to the nonmetal

Practice NAMING Binary Ionic Compounds MetalCation(+)NonMetalAnion (-) Compound Formula Compound Name SodiumNa +1 OxygenO -2 Na 2 O Sodium oxide AluminumAl +3 SulfurS -2 Al 2 S 3 Aluminum sulfide MagnesiumMg +2 PhosphorusP -3 Mg 3 P 2 Magnesium phosphide PotassiumK +1 SeleniumSe -2 K 2 Se Potassium selenide

Writing Covalent Compounds – Add prefixes to show HOW MANY atoms of each element are in the compound – Compound Ends in -ide

PRACTICE

Polyatomic Ions

– Positively or negatively charged – Covalently bonded – Contains two or more atoms

Polyatomic Ions to Know.... Charge NameFormula 1 +AmmoniumNH₄ 1 - Acetate Chlorate Hydroxide Nitrate C₂H₃O₂ ClO₃ OH NO₃ 2 - Carbonate Sulfate CO₃ SO₄ 3 –PhosphatePO₄ POLYATOMIC IONS Positive or Negative Compounds COVALENT Bonds (sharing electrons) Contain 2 or MORE atoms

Writing Formulas Examples Calcium Nitride Carbon Trioxide Sodium Nitrate Potassium Hydroxide Magnesium Oxide Sulfur Diphosphide Aluminum Sulfate Ammonium Phosphate