IONIC AND COVALENT BONDS 4 TH BLOCK CHEMISTRY

WARM-UP 1.What is the trend of valence electrons on the periodic table? 2.What is the trend of the ion charges?

THINGS TO REMEMBER: 1.What is a cation? 2.Which type of elements form cations? 3.What is an anion? 4.Which type of elements form anions?

IONIC COMPOUNDS Composed of cations and anions Metal + Nonmetal Transfer of electrons (use arrows in Lewis dot structures) so that atoms can obtain the electron configurations of noble gases Ex: Sodium Chloride  Table Salt  Na + cations and Cl - anions

IONIC COMPOUNDS Even though IONic compounds are composed of IONS (which have charges), ionic compounds are electrically neutral because the total positive (+) charge of the cations = the total negative (-) charge of the anions Ex: Na + and Cl - : the +1 charge of the sodium cation cancels out the -1 charge of the Chloride anion +1 + (-1) = 0

CHEMICAL FORMULA Kinds and numbers of atoms in the smallest representative unit of a substance Does not represent a single distinct unit because ionic compounds exist as a collection of positively and negatively charged ions in repeating patterns. Refers to the formula unit. Ex: NaCl

IONIC COMPOUNDS EXIST IN REPEATING 3-D PATTERNS

FORMULA UNIT Lowest whole-number ratio of ions in an ionic compound Only for ionic bonds NOT covalent bonds Ex: Magnesium Chloride

PROPERTY OF IONIC COMPOUNDS: CRYSTALLINE SOLIDS AT ROOM TEMPERATURE

PROPERTIES OF IONIC COMPOUNDS Ionic compounds exist in Repeating 3-D Patterns- Crystalline Solids at room Temperature Generally have high melting points Can conduct electric current when melted or dissolved in water (often water soluble) Aragonite (CaCo 3 )

COVALENT BONDING Attractions between ions fail to explain bonding Do not give up or accept electrons

COVALENT BONDS Atoms held together by SHARING electrons Nonmetal+ nonmetal Atoms want to obtain the electron configurations of noble gases

MOLECULE Neutral group of atoms (2 or more atoms) joined together by COVALENT bonds

MOLECULAR COMPOUND A compound composed of molecules  only covalent bonds Ex: H 2 O

PROPERTIES OF MOLECULAR COMPOUNDS OR COVALENT COMPOUNDS Relatively lower melting and boiling points than ionic compounds Gases or liquids at room temperature Often not soluble in water- solutions don’t conduct electricity

MOLECULAR FORMULA Chemical formula of a molecular compound – shows the kinds and numbers of atoms present in a molecule of a compound

MOLECULAR FORMULA Reflects the actual number of atoms in each molecule The subscripts are not necessarily lowest whole- number ratios

SINGLE COVALENT BONDS 2 atoms held together by sharing a pair of electrons Ex: H 2 - molecular formula Structural formula: represented with dashes

UNSHARED OR LONE PAIRS OF ELECTRONS a pair of electrons that is not shared between atoms Find lone pairs in F 2

COMPOUND EXAMPLES A substance that contains 2 or more elements chemically combined in a fixed proportion Ex: H 2 O (water), NH 3 (Ammonia)

WARM-UP How many valence electrons does group 1 have? Group 2? Group 13? Group 14? 15? 16? 17? 18? What are the charges of the resulting ions in each of these groups?

DOUBLE AND TRIPLE COVALENT BONDS atoms form double or triple covalent bonds if they can obtain a noble gas structure by sharing 2 or 3 pairs of electrons

DOUBLE COVALENT BOND A bond that involves two shared pairs of electrons Ex: O 2, CO 2

TRIPLE COVALENT BOND A bond formed by sharing 3 pairs of electrons Ex: N 2

POLYATOMIC IONS Ions composed of more than one atom that are covalently bonded with a charge Ex: NH 4 + Important component of fertilizer for field crops, home gardens, and potted plants

YOU TRY: H 3 O + : hydronium ion Found in acidic mixtures like lemon juice

TYPES OF CHEMICAL BONDS WORKSHEET Try #s

SUMMARY Contrast Ionic and Covalent Bonds.

NAMING IONIC AND COVALENT BONDS

EXIT TICKET 1.In your own words define covalent bonding and ionic bonding. 2.Contrast the properties of covalent and ionic bonds. 3.What rules did you discover about naming binary ionic compounds composed of main group elements? (activity 1) 4.What rules did you discover about naming binary compounds containing variably charged cations? (activity 2) 5.What rules did you discover about naming ionic compounds containing polyatomic ions? (activity 3) 6.What rules did you discover about naming binary compounds of the nonmetals? (activity 4)