Chapter 7 and 8 notes
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Chapter 7 and 8 notes

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chemistry, ionic and covalent bonding, electron configurations, counting molecules and atoms.

chemistry, ionic and covalent bonding, electron configurations, counting molecules and atoms.

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Chapter 7 and 8 notes Chapter 7 and 8 notes Presentation Transcript

  • Chapter 7 and 8 Ionic and Covalent Bonding
  • 7.1 Ions • Valence Electrons are the electrons in the highest occupied energy level of an element’s atoms. • The number of valence electrons determines the chemical properties of an element. • To find the number of valence electrons in an atom of a representative element, look at the group number. (see table 7.1)
  • Valence Electrons • Valence electrons are usually the only electrons used in chemical bonds, so they are show in electron dot structures. • In forming compounds, atoms tend to achieve the electron configuration of a noble gas. • This is called the Octet Rule. • All atoms want to have 8 electrons in their outer or valence shell.
  • Formation of Cations • Atoms of the metallic elements tend to lose their valence shell electrons leaving 8 in the next level down. • An atom’s loss of valence of electrons produces a cation, or positively charged ion. • Remember, an ion is a charged atom that has lost or gained electrons during the chemical bonding process.
  • Neutral Sodium Atom + Na Whoa…I just got smaller…
  • Neutral Chlorine Atom Cl Now I’m bigger and stronger….
  • Transition Metals • For transition metals, the charges of cations may vary. • For example, elements such as iron, nickel and copper may lose 1 to three electrons depending on the chemical compound.
  • Formation of Anions • A anion is an atom or group of atoms with a negative charge. • The gain of a negatively charged electron by a neutral atom will create an anion. • Non-metals typically form anions. • The name of the anion is not the same as the name of the atom. • It usually ends in –ide. (See table 7.2)
  • Vocabulary Cards • Valence electron • Octet Rule • Transition Metal
  • SUM IT UP Name the following ions properly. FClCa+2 O-2
  • Electron Configurations • An electron configuration is a way to show the electrons in a particular atom in the proper order. • Since electrons are arranged in shells, each shell has a different name. • Use the periodic table to figure out the electron configuration for any atom.
  • LET’S PRACTICE! 1s 2s 2 1 1s 2s 2p 2 2 5 1s 2s 2p 3s 3p 2 10 3 4s 3d 4p 2 2 6 2 6
  • Vocabulary Cards • Electron configuration
  • POST IT UP What is the electron configuration for carbon? I S! TH OT IG IN EE DH EL P!
  • 7.2 Ionic Bonds and Ionic Compounds • Compounds composed of cations and anions are called ionic compounds. • Ionic compounds are usually composed of a a metal and other nonmetals. • Although they are composed of ions, they are electrically neutral…meaning no charges or their charges cancel out. • Bonds that hold ionic compounds together are called ionic bonds.
  • Formula Units • A chemical formula shows the kinds and numbers of atoms in the smallest representative unit of a substance. • A formula unit is the lowest wholenumber ratio of ions in an ionic compound. • The chemical formula is not always the lowest whole number ratio.
  • Let’s Practice • How many kinds of atoms are in each of these ionic compounds? • NaCl • MgCl2 • Ca(OH)2 • Ca3(PO4)2
  • Properties of Ionic Compounds • Most ionic compounds are crystalline solids at room temperature. • Ionic compounds generally have high melting points. • Ionic compounds can conduct an electric current when melted or dissolved in water.
  • Vocabulary Cards • Ionic Bond • Formula Unit
  • SUM IT UP How many kinds of each of these atoms are in this compound? Ca (C2H6O2)2
  • 8.1 Molecular Compounds. • Some compounds are not ionic. • Instead of giving or taking electrons, these compounds share electrons to complete their Octet. • This is called a covalent bond. • A molecule is a neutral groups of atoms joined by a covalent bond. • A diatomic molecule is a molecule consisting of only two atoms. • A compound composed of molecules is called a molecular compound.
  • Molecular Formulas • A molecular formula is the chemical formula of a molecular compound. • It shows how many of each element a molecule contains. • A molecular formula does not tell you about a molecule’s structure.
  • 8.2 The Nature of Covalent Bonding • In forming covalent bonds, electron sharing usually occurs so that atoms attain the electron configuration of a noble gas. • Combinations of nonmetallic elements in groups 4A, 5A, 6A and 7A are likely to form covalent bonds. • They share electrons to achieve an octet like a noble gas.
  • Diagrams • An electron dot diagram represents the shared pairs of electrons in a molecule. • Each bond is two electrons or two dots. • A structural formula represents the covalent bonds by dashes and shows the arrangement of the atoms. • Each dash will equal two electrons. • A pair of valence electrons not shared between atoms is called an unshared pair, lone pair or nonbonding pair.
  • Lone unshared pairs
  • Polyatomic ions • A polyatomic ion is a tightly bound group of atoms that has a positive or negative charge and behaves like a unit. • A group of atoms may be covalently bonded as a polyatomic ion but since the whole unit has a charge, it can bond with other charged ions.
  • Vocabulary Cards • Covalent bond • Molecule • Polyatomic ion • Unshared pair
  • SUM IT UP Draw the structural diagram for water.
  • 8.4 Polar Bonds and Molecules • Covalent bonds involve sharing between atoms. • However, some atoms are more electronegative than others meaning they tend to attract more electrons than other atoms. • When all the electrons are shared equally, it is a nonpolar covalent bond. • When one atom attracts electrons more strongely than the other atom, a polar covalent bond forms. • The atom that attracts more electrons become slightly negative while the other becomes slightly positive. • This is NOT the same as an ionic bond with normal charges!
  • Hydrogen Bonds • Hydrogen bonds occur when a hydrogen that is covalently bonded to another atom will be weakly attracted to another atom on another molecule. • The partial positive charge of the hydrogen in the polar molecule, gets attracted to the partially negative charge on another molecule. • Water usually forms hydrogen bonds. • As a result, life is possible.
  • Vocabulary Cards • Polar molecule • Hydrogen bond
  • POST IT UP Why is water polar? I S! TH OT IG IN EE DH EL P!
  • Science Swag Create an accurate model for a chemical compound. Label the atoms and the bonds. Bigger models with more atoms get more points.