Warm-up Determine the number of valence electrons and the charge of an atom of these elements: Example: Chlorine: 7 valence electrons and -1 charge Beryllium Be: 2 valence and Be+2 Sulfur S: 6 valence and S-2 Fluorine F: 7 valence and F-1 Oxygen O: 6 valence and O-2

Unit Four, Day One Kimrey 26 September 2012 Chemistry Unit Four, Day One Kimrey 26 September 2012

Its what happens when elements fall in love! Chemical Bonding Its what happens when elements fall in love!

3 Types of Bonds Covalent bonding Ionic bonding Metallic Bonding

Covalent Bonding -The perfect relationship Bond is formed by the sharing of electrons between two nonmetals. Two types of covalent bond polar and nonpolar. Polar covalent bond- unequal sharing of electrons. Nonpolar covalent bond- equal sharing of electrons.

Ionic bonding -The stage five clinger One element steals all the electrons from another. -or more technically A transfer of valence electrons between a cation (+) and an anion (-). Typically between a metal and nonmetal or a metal and polyatomic ion. ex. NaCl, LiF, CaF2 Polyatomic ion- a group of bonded atoms that have a charge. ex. OH-, SO42-, etc.

Metallic Bonding -when two people merge into one. Between two metals and forms a sea of electrons. Attraction between the positive nucleus and surrounding electrons. Forms a sea of electrons. This is why metals are malleable and ductile. Electrons don’t belong to either element – instead just float around the nuclei

NEGATIVE POSITIVE ION CATION ANION Answer these questions: An atom that gains one or more electrons will have a ____________________ charge. An atom that loses one or more electrons will have a ____________________ charge. An atom that gains or loses one or more electrons is called an ____________. A positive ion is called a ______________ and a negative ion is called an _______________. NEGATIVE POSITIVE ION CATION ANION

ELECTRONS COMPLETE METAL NONMETAL What is an ionic bond? Atoms will transfer one or more ________________ to another to form the bond. Each atom is left with a ________________ outer shell. An ionic bond forms between a ___________ ion with a positive charge and a ________________ ion with a negative charge. Example B1: Sodium + Chlorine Example B2: Magnesium + Iodine ELECTRONS COMPLETE METAL NONMETAL

SHARE COMPLETE NONMETAL What is a covalent bond? Atoms ___________ one or more electrons with each other to form the bond. Each atom is left with a ________________ outer shell. A covalent bond forms between two _________________. Example C1: Hydrogen + Hydrogen Example C2: 2 Hydrogen + Oxygen SHARE COMPLETE NONMETAL

Electronegativity The ability of an atom in a compound to attract valence electrons to itself. Scale of 0-4 Differences in electronegativity is used to determine the type of bond. 0-0.4 = Nonpolar covalent 0.4-1.7 = Polar Covalent 1.7-4.0 = Ionic Example: Sodium bonded to bromine

Practice Identify the following bonds as polar or non-polar covalent: H bonded to O H bonded to C C bonded to F C bonded to N

Formulas for Ionic Compounds Ionic compounds will bond in a ratio that cancels their ion charge ALL compounds no matter what are neutral

Steps for Writing Formulas Find the charges of the elements. Find the simplest ratio needed to cancel out the charges. Write the ratio numbers as subscripts (ones do not get written!) Write the positive ion first followed by the negative ion. Make sure not to write the charges of the ions in the formula.

Examples Sodium and Chlorine NaCl Potassium and Iodine KI Calcium and Bromine CaBr2 Barium and Oxygen BaO

Those pesky polyatomics. Polyatomic is a group of bonded atoms that still has a charge. Same steps as binary compounds plus… 5. If a subscript is added to a polyatomic ion place the entire polyatomic in (). REMEMBER! Never ever change the subscripts in a poly-atomic ion.

Examples Sodium and Hydroxide (OH-1) NaOH Lithium and sulfate (SO4-2) Li2SO4 Calcium and phosphate (PO4-3) Ca3(PO4)2 Ammonium and fluorine (NH4+1) NH4F

What does all this mean? The chemical formula tells you the number of each element in that compound.

A positively charged ion 1. Complete the chart using your knowledge of atoms. Vocab Review 1 – What do we call the electrons in the outermost energy level? 2 – What term refers to an atom that has lost or gained electrons? 3 – What is a cation? 4 – What is an anion? Valence Electrons Ions A positively charged ion A negatively charged ion

2. Ionic Bonds - Draw the Lewis structures for each atom, draw arrows to show the transfer of electrons, write the charge for each ion, and then write the chemical formula. (A) Potassium + Iodine (B) Magnesium + Oxygen (C) Lithium + Nitrogen

3. Covalent Bonds – Draw the Lewis structures for each atom, draw circles to show the electrons that are shared, and then write the bond structure and chemical formula. (A) Fluorine + Fluorine (B) 3 Hydrogen + 1 Phosphorus (C) 2 Hydrogen + 1 Sulfur

Potassium + Iodine Sodium + Oxygen Calcium + Chlorine Aluminum + Chlorine

Chlorine + Chlorine Oxygen + Oxygen Carbon + 2 Oxygen Carbon + 4 Hydrogen

What about other metals? Other metals charges will always be given in roman numerals. e.g. I,II, IV These charges are always positive. What is the charge of Iron (II)? 2+