Presentation on theme: "Chapter 6: Chemical Bonds"— Presentation transcript:
1Chapter 6: Chemical Bonds 6.1 Ionic BondingChapter 6: Chemical Bonds
2Stable Electron Configurations If highest energy level of an atom is filled with e-, the atom is stable and not likely to reactChemical properties of an element depend on the number of valence electronsElectron (Lewis) dot diagram = model in which each dot represents a valence electron
3Stable Electron Configurations Highest energy level of a noble gas atom is completely filledNoble gases have stable electron configurations with 8 valence electrons (two electrons in helium).Elements tend to react to get electron configurations similar to noble gases
5Chemical bondingElements can get a stable electron configuration by transferring of electronsEx: A chlorine atom has one electron fewer than an argon atom, adding one electron would give chlorine a stable configurationEx: A sodium atom has one more electron than a neon atom, removing one electron would give sodium a stable configuration.
6Chemical bondingWhen sodium reacts with chlorine, an electron is transferred from sodium atom to chlorine atomEach atom ends up with a more stable electron arrangement than it had before transfer
8Formation of Ions Ionic Bonds = transfer of electrons When an atom gains or loses an electron, the number of protons does not equal number of electronsCharge on the atom is not balanced, and atom is not neutralIon = Atom that with positive or negative chargeCharge on an ion is represented by a plus or a minus signNegative charge = anionPositive charge = cation
9Ionic BondsEx: Ion that forms when a chlorine atom gains an electron has 17 protons and 18 electronsThis ion has a charge of 1–.The symbol for the ion is written Cl1–, or Cl– for short.Anions like the Cl– ion are named by using part of the element name plus the suffix –ide. Thus, Cl– is called a chloride ion.
10Ionic Bonds Sodium ion has 11 protons and 10 electrons. The sodium ion has a charge of 1+.The symbol for the ion is written Na1+, or Na+ for short.An ion with a positive charge is a cation.A cation uses the element name, as in the sodium ion.
11Formation of Ionic Bonds A particle with a negative charge will attract a particle with a positive chargeChemical bond = force that holds atoms or ions together as a unitIonic bond =force that holds cations and anions together, forms when electrons are transferred from one atom to another (metal and non-metal)
12Ionization EnergyCations (+) form when electrons gain enough energy to escape from atomsEnergy allows electrons to overcome the attraction of the protons in the nucleusIonization energy = of energy used to remove an electronsThe lower the ionization energy, the easier it is to remove an electron from an atom
14Ionic CompoundsCompounds that contain ionic bonds are ionic compounds, can be represented by chemical formulasChemical formula = shows what elements are in a compound, and how many of eachEx: Chemical formula for sodium chloride, NaCl, indicates one sodium ion for each chloride ion in sodium chloride
15Binary ionic compounds Compound made from only two elements is a binary compoundThe names have a predictable pattern:The name of the cation followed by the name of the anion.Examples: sodium chloride
16Describing ionic compounds Formula of an ionic compound describes the ratio of the ions in the compound2 different compounds of copper and oxygen are belowHas to be at least two names to distinguish red copper oxide from black copper oxide.
17Polyatomic ionsPolyatomic ion = covalently bonded group of atoms that has a positive or negative chargeMost simple polyatomic ions are anions
18Ionic CompoundsWhat is the chemical formula for magnesium chloride?
19Ionic CompoundsWhat is the chemical formula for magnesium chloride?MgCl2
20Naming ionic compounds Write the name of the metal first and then the nonmetal.Add an -ide ending to the non-metalUse Roman Numerals to indicate charge on a transition metalIonic compounds involving polyatomic ions follow the same basic rule:Write the name of the metal first,Then the name of the polyatomic anions
25Sharing electronsWhen two atoms share one pair of electrons, the bond is called a single bondHydrogen atom has one electron, if had two electrons, it would have the same electron configuration as a helium atomTwo hydrogen atoms can achieve a stable electron configuration by sharing their electrons and forming a covalent bond
26Molecules of elementsMolecule = neutral group of atoms that are joined together by one or more covalent bondsMany nonmetal elements exist as diatomic moleculesDiatomic means “two atoms”
27Br-I-N-Cl-H-O-F Brinclhof Memory Trick:Br-I-N-Cl-H-O-FBrinclhofSounds like a German name.There’s also:I Brought Clothes For Our New Hamster… either way…
29Multiple covalent bonds 2 pairs of electrons shared = double bond3 pairs of electrons shared = triple bondNitrogen has five valence electrons.When the atoms in a nitrogen molecule (N2) share three pairs of electrons, each atom has eight valence electronsEach pair of shared electrons is represented by a long dash in the structural formula NN
30Unequal sharing of electrons Polar covalent bond = atom with the greater attraction for electrons has a partial negative chargeOther atom has a partial positive chargeHappens because the e- are closer to one atom than the other (one atom attracts e- more)Type of atoms in a molecule and its shape are factors that determine whether a molecule is polar or nonpolar
31Unequal sharing of electrons Except for noble gases, elements on the right of the periodic table tend to have a greater attraction for electrons than elements on the leftElements at the top of a group tend to have a greater attraction for electrons than elements at the bottom of a group have.
32Polar covalent bondCovalent bonds= atoms attract electrons equally and are shared equally
33Attraction between molecules Attractions between polar molecules are stronger than attractions between nonpolar moleculesBonds between polar molecule are stronger than non polar
34Naming covalent bonds Prefixes tell you how many of each atom you have Prefix goes in front of the element nameMono- 1Di -2Tri – 3Tetra -4Penta – 5Hexa – 6Hepta – 7