The attraction of opposites IONIC BONDING The attraction of opposites

What Is an Ionic Bond? An ionic bond is the attraction of two oppositely charged ions. These ions combine and the opposite charges cancel each other out like the electrons and protons of an atom. Combining the ions of different elements creates new matter that is useful to the world today. For example, when a sodium atom bonds with a chlorine ion, they form sodium chloride which is table salt.

Electron Transfer When an atom has less than eight valence electrons it is not chemically stable and must get chemically stable, It will lose electrons or gain electrons to fill its last energy level and therefore become chemically stable.

Ionic Bonding Metals will always lose electrons to become chemically stable Metals will form positive ions Non metals will always gain electrons to become chemically stable Nonmetals will always form negative ions

Example Of An Ionic Bond When a sodium atom and a chlorine atom combine, sodium’s one valence electron gets transferred or moved to the chlorine atom. Both atoms are now ions; sodium is positive and chlorine is negative. The ions attract each other and bond. These two form Sodium Chloride, which is table salt.

Diagram: Na + Cl Sodium’s 1 valence electron is transferred to Chlorine.

Result: Na + Cl  NaCl Sodium is now stable too (8 valence electrons). Chlorine is stable (8 valence electrons).

Forming Ionic Bonds Things to remember! An ionic bond is the attraction between two oppositely charged ions. Oppositely charged ions attract each other. Ionic bonds are formed when electrons are taken and not shared.

Pictures of Forming Ionic Bonds The ions attract each other. Therefore, they bond.

Ionic bonding forms compounds Ionic bonding doesn’t form molecules The oppositely charged ions are attracted to each other – forming very strong bonds!!

Crystal Shape Every ion in an ionic bond is attracted to ions near it that have an opposite charge. Because of this, all the ions attract many ions. Therefore, they create a shape. This shape is 3-D and is called the crystal shape.

Characteristic of ionic bonds: Crystal Shape Ionic solids are generally high melting points Ionic solids are hard and brittle Ionic solids conduct electricity only when they are dissolved in water

Electrical Conductivity When ionic compounds are dissolved in water, they conduct electricity. When they are solid, they don’t conduct. The ions are tightly bound together and have no room to move or let the electricity flow through. When dissolved, the ions move more freely; therefore, electricity can flow through them.

High Melting Points Ionic Bonds are very strong. It takes a lot of heat (energy) to make the particles have enough energy to overcome the attractive forces. Ionic bonds are so strong that all ionic bonds are solids at room temperature.

Elements Which Form This Bond Metal + Nonmetal = Ionic Bond

Common Ions Which Form This Bond Lithium Sodium Potassium Calcium Magnesium Aluminum Oxide Fluoride Chloride Iodide Sulfide

Pictures Of Atomic Bonds Covalent Bond Ionic Bond

Polyatomic Ions A Polyatomic ion is an electrically charged collection of more than one atom. Polyatomic ions usually have a charge because the collection of atoms has either gained or lost an electron. Each polyatomic ion has an overall positive or negative charge. If a polyatomic ion combines with an ion of an opposite charge, an ionic compound forms.

Example of A Polyatomic Ion Carbonate ion (CO32-), made of 1 carbon atom & 3 oxygen atoms. Combines with Calcium ion (Ca2+). Makes Calcium Carbonate (CaCO3)

Did You Understand? What properties do ionic compounds have? Why are ions in ionic compounds attracted to each other? What are polyatomic ions? What is the process of Ionic Bonding? Summary: What is an Ionic Bond?

Covalent Bonding

Covalent Bonding Covalent Bond: a bond formed by the sharing of electrons between atoms. (does NOT form charges) Made up of nonmetals Molecule: a neutral group of atoms joined together by covalent bonds. (Compounds formed with ionic bonds do NOT have molecules) Molecular Formula: chemical formula for a molecular compound. It shows how many atoms of each element a molecule contains.

Covalent Bonding Examples: ascorbic acid (vitamin C): C6H8O6 trinitrotoluene (TNT): C7H5N3O6 C_____, H_____, N_____, O_____, 6 8 6 7 5 3 6

Molecular Nomenclature Prefix System (binary compounds) Less electronegative atom comes first. 2. Add prefixes to indicate # of atoms. Omit mono- prefix on first element. 3. Change the ending of the second element to -ide. most

Molecular Nomenclature PREFIX mono- di- tri- tetra- penta- hexa- hepta- octa- nona- deca- NUMBER 1 2 3 4 5 6 7 8 9 10

Naming Covalent Binary Compounds diphosphorus pentoxide P2O5 = CO2 = carbon dioxide CO = carbon monoxide N2O = dinitrogen monoxide phosphorous pentachloride = PCl5 dinitrogen tetrahydride = N2H4 dichlorine heptaoxide = Cl2O7 iodine dioxide = IO2

X O Lewis Structures Electron Dot Diagrams show valence e- as dots distribute dots like arrows in an orbital diagram EX: oxygen X O

Ne Lewis Structures Octet Rule Most atoms form bonds in order to obtain 8 valence e- Full energy level stability ~ Noble Gases Ne

Diatomic Molecules Diatomic Molecule: a molecule consisting of two atoms. Diatomic molecules in nature: H2, N2, O2, F2, Cl2, Br2, I2

Cl Cl O O N N #s of Covalent Bonds Single Bond: 2 e- shared Double Bond: 4 e- shared Triple Bond: 6 e- shared

Polyatomic Ions and covalent bonding “CHLORATE” -1 Chlorine has 7 valence e- O Cl O Each oxygen has 6 valence e- When ClO3 comes together they form 3 single covalent bonds One additional electron completes chlorine with a full valence shell, making this a covalently bonded group with an ionic charge of -1

Polarity

Bond Polarity Most bonds are a blend of ionic and covalent characteristics. Difference in electronegativity determines bond type. E difference: >1.7 E difference: 0.4-1.7 E difference: 0.0-0.4

Bond Polarity Electronegativity Attraction an atom has for a shared pair of electrons. higher e-neg atom  - lower e-neg atom +

Bond Polarity Electronegativity Trend Increases up and to the right.

Table of Electronegativity

Bond Polarity Nonpolar Covalent Bond e- are shared equally symmetrical e- density usually identical atoms

+ - Bond Polarity Polar Covalent Bond e- are shared unequally asymmetrical e- density results in partial charges (dipole) + -

Bond Polarity Nonpolar Polar Ionic e- shared equally e- shared unequally Ionic e- transferred E difference: 0.0-0.4 E difference: 0.4-1.7 E difference: >1.7

Bond Polarity - + Nonpolar Covalent – equally shared e- Polar Covalent - partial charges, e- shared unequally + -

Polar Molecule One end of the molecule is slightly negative and the other end is slightly positive Caused by the presence of a polar bond in the molecule. (structure is not symmetrical) A molecule that has two poles is called a dipolar molecule, or dipole.

Self Test . . O C : Is CO2 a covalent or ionic compound? What is CO2 ’s name? What is the electronegativity difference between C and O? Does CO2 have polar bonds? Is CO2 a polar molecule overall? . . O C :

Bonding Summary Ionic Covalent Transfer of electrons Octet achieved by: Transfer of electrons (forming + & - ions) Sharing electrons Made of: Metal cation (+) & Nonmetal anion (-) Nonmetals (above metalloid line) (no charges) Characteristics: Brittle Soft and Squishy Structure: Arranged in alternating + & - ions (crystal lattice) Individual molecules Representative Particle: Formula Unit: (lowest whole number ratio of atoms) Molecule: (group of joined atoms)

Yes, when dissolved in water or melted Bonding Summary Ionic Covalent Physical State: Solid Solid, Liquid, Gas Melting Point: High Low Electrical Conductivity: Yes, when dissolved in water or melted No

Quiz - answer the following on a sheet of paper The following ball-and-stick molecular model is a representation of thalidomide, a drug that causes birth defects when taken by expectant mothers but is valuable for its use against leprosy. The lines indicate only the connections between atoms, not whether the bonds are single, double, or triple (red = O, gray = C, blue = N, ivory = H): (a) What is the molecular formula of thalidomide?

2. Above is a ball-and-stick molecular model representation of acetaminophen, the active ingredient in such over-the-counter headache remedies as Tylenol (red = O, gray = C, blue = N, ivory = H): (a) What is the molecular formula of acetaminophen?