Presentation on theme: "Ionic Covalent Metallic"— Presentation transcript:
1Ionic Covalent Metallic Bonds and bondingIonicCovalentMetallic
2Ionic Bonds Electrons are transferred from one atom to another. Compounds are made.Involves a metal and a nonmetalMetal : donates electron(s) so it becomes a positive ion (cation)Nonmetal receives electron and becomes a negative ion (anion)So...must have a cation and anion
3Why do ions exist?Atoms want a full outer shell of valence electrons (8).Will gain or lose electrons to achieve this = Octet ruleThen, positive and negative ion attract (bond)
19What ions exist in our water supply? IronCauses rust spots, dingy clothesCopper from ground and pipesCauses green residueChlorine and fluorine added to city waterBad heavy metals: mercury, arsenic, lead
20Calcium—contributes to “hard water” Scaling in showers, on cookwareBathtub ringBinds to soap and renders in inactiveWon’t latherFlat hair
25Covalent Bonds Electrons are shared between atoms Involves 2 or more nonmetalsWant to fulfill the octet rule.Molecules are made.Properties are a result of bond type(Polar and nonpolar will be discussed later)
27When the repulsive forces are overcome, the atoms can bond.
28Energy is released when bonds are made, and when bonds are broken. This energy can be measured.How? Heat released, light, etc.The same amount of energy that is required to make a bond is needed to break the bond.Energy in = Energy out
29Covalent bonds:Can be measured: Bond length is the distance between 2 nuclei.
30Are flexible: vibrate like a slinky, so bond length is variable. The longer the bond length, the weaker the bond (lower energy).The shorter the bond, the stronger the bond (higher energy).
32Properties of covalent molecules. 1. Can be a solid, liquid, or gas.The intermolecular attraction between molecules is much weaker than ionic.Gases: very weak intermolecular forces, so molecules are spread apart
41Properties of Metallic bonds 1. Shiny solids 2. Malleable (flattens out) and ductile (can be stretched into wires)
42Pretty high melting points Insoluble in water.5. Highly conductive
43Polar covalent bonds:Have an uneven distribution of electrons/shared unevenly.Polar ends have a partial “charge”. More like a pull.Structure is bent.
44Nonpolar covalent bond: Even distribution of electrons between atoms.No partial charge.Structure is usually linear (straight).
45Using electronegativity values to predict bond type: Electronegativity: a measure of an atom’s tendency to attract electrons.Higher value = stronger pull.We use the difference between the electronegativity values of the atoms in a molecule.
47If the electronegativity difference is: less than 0.5, then the bond is nonpolar covalent.between 0.5 and 1.6, the bond is considered polar covalentgreater than 2.0, then the bond is ionic.between 1.6 and 2.0:if a metal is involved, then the bond is ionic.If only nonmetals are involved, the bond is polar covalent.
48But….structure is overriding factor Examples:Sodium chloride: NaClNa = Fluorine = 3.1= ionicNitrogen dioxide: NO2N = O = difference = nonpolar covalentCarbon dioxide: CO2C = O = difference = .9But….structure is overriding factor
49So….The type of elements involved is the key determiner between ionic and covalent, and…The structure of the molecule is the overriding factor in determining polarity.
50How do we know the shape? Lewis dot structures Dots represent valence electrons.Allow us to determine polarity.Satisfies octet rule.
53Lewis dots with double bonds: Any unshared electrons will form a double or triple bond.Example: carbon dioxidePractice: C2H4
54Naming Covalent Compounds: Must specify how many of each element there is (unlike ionic compounds)Ionic: MgCl2 is magnesium chlorideCovalent: CCl2 is carbon dichloride.Why?
55How do we know whether it is an ionic or covalent compound? Ionic is a metal and nonmetalCovalent is only nonmetals
56Naming covalent compounds: Say the first element, then the second, indicating how many of each elementSecond elements may have different wordingi.e. sulfur is sulfide, oxygen is oxideDo not say “mono” for first element.