Ionic, Metallic and Covalent Compounds Everything together
Today’s Goal • How the objective will be completed? • Identify an elements’ oxidation number. Describe/explain how the oxidation number (charge) of an element is determined. • Given a specific number of protons, electrons, and neutrons, determine if it is a cation, anion, or neutral atom. Why would it be classified this way? • Which of the following compounds has the highest melting point or conductivity? How can you tell by looking at the periodic table? • Know what type of bonding elements like Copper exhibit. • If there is an element from Group 1 that bonds with an element from Group 17, what would the formula be? What other Group pairings will create the same type of formula? • First day Objective • By the end of the class period, you will: • Differentiate between ionic, covalent, and metallic bonds as well as know their properties. • Know the differences in the physical and chemical properties associated with ionic, covalent, and metallic bonding (conductivity, malleability, melting point, etc). • Distinguish between ionic, metallic, and covalent bonding using Lewis dot Diagrams and chemical formulas.
Chemical Bonds • Chemically combining of two or more atoms • Ionic Bonds • Metallic Bonds • Covalent Bonds Metallic Bonding
TERMS In your journal, copy all terms as written or rephrase in your own words. (total slides with vocabulary = 3) • ION: An atom or group of atoms that lost or gained electrons and has a charge • ANION: A negatively charged atom or group of atoms. Has gained one or more electrons • CATION: A positively charged atom or group of atoms. Has lost one or more electrons • OCTET RULE: All atoms need 8 valence electrons, Except H, He, Li, Be – 2 only • CHEMICAL FORMULA: A representation of a substance using symbols for its constituent elements
MORE TERMS • FORMULA UNIT: The smallest repeating unit of a substance. The molecule for nonionic substances. Also called the Empirical formula • IONIC BOND: A chemical link between two atoms caused by the electrostatic force between oppositely-charged ions in an ionic compound. • COVALENT BOND: a chemical link between two atoms in which electrons are shared between them. • POLYATOMIC ION: Two or more nonmetals combined together with a charge (YOU MUST KNOW THE LIST)
AGAIN EVEN MORE • VALENCE ELECTRONS: an electron that is the most likely to be involved in a chemical reaction. They are typically the highest energy s and p electrons. • COMPOUNDS: 2 or more DIFFERENT atoms combined • MOLECULE: 2 or more atoms COVALENTLY Bonded • MONATOMIC ION: An ion made up of only one type of element.
Ionic Bonding • Anions and cations are held together by opposite charges (+ and -) • Ionic compounds are called salts. • Simplest ratio of elements in an ionic compound is called the formula unit. • The bond is formed through the transfer of electrons (lose and gain) • Normally has a metal and a nonmetal or one or more Polyatomic Ions. • Electrons are transferred to achieve noble gas configuration.
Properties of Ionic Compounds • Electrons are transferred (Made of Ions) • Metal and a Nonmetal present (except NH4+ may be present) • High Melting Points • High Boiling Points • Normally Solids at Room Temperature • Conduct electricity, allowing ions to move, when liquid or dissolved (next slide) • In a solid, the ions are locked in place so they are insulators. • Normally dissolve in Water • Made of positive and negative ions • Electrons are localized on ions
+ - - - - - - - - - - - - - - - - - - - - - - - - - - - - An electron is transferred from the sodium atom to the chlorine atom + Na Cl
+ - - - - - - - - - - - - - - - - - + - - - - - - - - - - - Both atoms are happy, they both achieve the electron arrangement of a noble gas. Notice 8 e- in each valence shell!!! -1 +1 Na Cl
Ionic Bonding Lets do an example by combining calcium and phosphorus: You try! • All the electrons must be accounted for, and each atom will have a noble gas configuration (which is stable). Ca P
Ionic Bonding = Ca3P2 Formula Unit This is a chemical formula, which shows the kinds and numbers of atoms in the smallest representative particle of the substance. For an ionic compound, the smallest representative particle is called a: Formula Unit
Metallic Bonds are… • How metal atoms are held together in the solid. • Metals hold on to their valence electrons very weakly. • Think of them as positive ions (cations) floating in a sea of electrons.
Properties of Metallic Compounds • WILL NOT dissolve in water • Will conduct electricity when solid • Malleable (hammered into shapes) and Ductile (drawn into thin wires) • Both malleability and ductility explained in terms of the mobility of the valence electrons • Most Solids at well above room temperature • High Melting and Boiling Points • Made of Positive Ions and delocalized electrons • Lustrous
Metals Form Alloys Metals do not combine with metals. They form alloys which is a solution of a metal in a metal. Examples are steel, brass, bronze and pewter.
SCl2 can’t be an ionic compound because sulfur and chlorine are both non-metals: they both need to gain extra electrons to become stable.Remember, for an ionic bond to form, you need an electron giver and an electron taker.
Draw dot diagrams to show how one S atom and 2 Cl atoms can share electrons so they each get that octet that all atoms want. Cl S Cl In a covalent compound, the shared electrons are counted by both atoms as part of their octets.
That’s what a covalent bond is:the bond that results when atoms share electrons. Sharing = Cooperating: When you see the “co” in covalent, think of cooperating and sharing.
How can you recognize a covalent compound when you see it?Hint: Look at these formulas again.MgCl2Al2O3SCl2K2SCO2
Covalent Bonds • A covalent bond is typically formed by two non-metals. • Non-metals have similar electronegativities. • Consequently, neither atom is "strong" enough to steal electrons from the other. • Therefore, the atoms must share the electrons. • Stable non-ionizing particles, they are not conductors at any state Except Polyatomic Ions themselves are covalent
Properties of Covalent Compounds • Electrons are shared (no ions) • Only Nonmetals present (NH4+ will be ionic) • Low Melting Points • Low Boiling Points • Normally Gases and Liquids or solids at Room Temp • Don’t conduct electricity • Normally DON’T dissolve in water • The larger the molecule the greater the chance it will be a solid at Room Temp • Made of Neutral Nonmetals and localized shared electrons
O O O N N O Covalent Bonds There can be as many as 6 e-s being shared between 2 atoms + N N + The more e-s shared the stronger the covalent bond.
Logical question at this point… How do you know which atoms are attached to which? Hints: a. Hydrogen can form only one bond, so it’s always on an end, never in the middle. b. Formulas are often written to show the order the atoms go in, so HCN is attached this way: H – C – N c. When a central atom has group of other atoms bonded to it, the central atom is usually written first, so CO3 would be: O – C – O O
Draw a dot diagram showing how ammonia, NH3, is a covalent compound. H N H H
More practice! 1. PCl3 2. H2 3. HCN 4. phosphate ion 5. SF2 6. CO 7. chlorite ion
Copy this in your journal and memorize! • There are general characteristics of each type of bonding: • Ionic: High melting points, most dissolve in water, conduct electricity when dissolved in water, brittle • Covalent: Low melting points, most do not dissolve in water, do not conduct electricity when dissolved in water • Polar covalent: Medium melting points, some dissolve in water, do not conduct electricity when dissolved in water • Metallic: Soft, conduct heat and electricity, do not dissolve in water