Ionic and Covalent Compounds Solubility and Electrical Conductivity

Please complete the warm-up on a sheet of paper Element Sodium Chlorine Family and Group #   Cation or Anion Oxidation Number/Charge Lewis Dot Structure

Chemical Bonds Chemically combining of two or more atoms Ionic Bonds Metallic Bonds Covalent Bonds Metallic Bonding

TERMS 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

MORE TERMS CHEMICAL FORMULA: A representation of a substance using symbols for its constituent elements 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.

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

Conductors and Conductivity There are many materials that allow charges to move easily. They are called conductors. Conductors have the quality of conductivity. The conductor is the object that allows charge to flow. Conductivity is a quality related to the conductor. A material that is a good conductor gives very little resistance to the flow of charge. This flow of charge is called an electric current. A good conductor has high conductivity.

Water/Electrical Conductivity Water itself is not a conductor of electricity. In order for a substance to carry charge, two conditions must first be met: There must be charged particles within the substance (either ions or electrons) and These particles must be free to move It is true that in water (H2O) the discrete molecules are free to move, however, they carry no charge. The only reason water can sometimes conduct electricity is because of the minerals (metallic solids) already present in the water.

Different Types of Conductors Metals are traditional conducting materials. There are some conductors that are not metals. Carbon is the best example. Ionic conductors is a solution such as saltwater has a lot of free ions floating around. Those ions (charged atoms) can flow easily, and ionic solutions are very good conductors.

Electrical Path Providing a path for charges to move, and making that path out of materials that allow easy movement, results in a flow of charge (electrons) called a current. The electrons will flow from a location that is negative to one that is positive. In the case of a battery connected to a conducting loop (called a circuit. )

Compounds and Electrical Conductivity Ionic Compounds Covalent Compounds

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) Electrons are transferred to achieve noble gas configuration.

Properties of Ionic Compounds Electrons are transferred (Made of Ions) Metal and a Nonmetal 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

Notice 8 e- in each valence shell!!! 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

Very Strong Electrostatic attraction established… IONIC BONDS

Which of these are not ionic compounds? MgCl2 Al2O3 SCl2 K2S CO2

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.

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 How can you recognize a covalent compound when you see it? Hint: Look at these formulas again. MgCl2 Al2O3 SCl2 K2S CO2

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

In Class Assignment 1 paper/team Where would be the worst place to be during a lightning storm? Ocean water, lake water or a bathtub full of Jello? - Graded Include a hypothesis statement – in your statement – include why Detailed experiment design – what is your procedure – materials used in experiment Data collection – what is your data to prove your hypothesis Experiment needs to be based on conductivity of electricity 20 minutes to complete detailed assignment Will present in class