1. Chemical Bonds Chapter 6

2. Review Atomic Structure – Protons (+) and Neutrons (N) make up the mass of and are contained in the nucleus or center of the atom – Electrons (-) orbit the nucleus in energy levels containing: Electron Nucleus 2 electrons in the first energy level 8 electrons in the second energy level 8 electrons in the third energy level Valence electrons are located in the outer energy level and determine the atoms ability to bond with other atoms to form compounds.

3. Stable Electron Configuration When the outer energy level is filled with electrons, the atom is stable and will not bond with other atoms. The chemical properties of an element depend on the number of valence electrons. Atoms will lose, gain, or share electrons to obtain a full outer energy level. Chemical bond is the force that holds atoms together to form compounds.

4. Electron Dot Diagrams Model of atoms in which each dot represents a valence electron.

5. Ionic Bonding Some elements obtain a full outer energy level by transferring electrons between atoms. Loosing one or more electrons forms a positive ion also called a cation. Gaining one or more electrons forms a negative ion also called anion Oppositely charged ions are attracted to one another and form an ionic bond/ionic compound.

6. The amount of energy required for an electron to escape the attraction of the positive protons in the nucleus is the ionization energy. Ionization energy increases from left to right in a period on the periodic table. Ionization energy decreases from top to bottom in a group on the periodic table. Metals (to the left side of the table) tend to lose electrons Nonmetals (to the right side of the table) tend to gain electrons

7. Ionic Compounds Two or more atoms held together by an ionic bond. Usually consist of a metal and a nonmetal Represented in a chemical formula – Shows the ratio of atoms of each element in the compound – MgCl 2

8. Section 1 Assessment Questions 1.When is an atom stable? a.when its electrons are evenly distributed through its energy levels b.when its lowest occupied energy level is filled with electrons c.when its highest unoccupied energy level is filled with electrons d.when its highest occupied energy level is filled with electrons

9. 1.When is an atom stable? a.when its electrons are evenly distributed through its energy levels b.when its lowest occupied energy level is filled with electrons c.when its highest unoccupied energy level is filled with electrons d.when its highest occupied energy level is filled with electrons

10. 2.Which description applies to an element that has two valence electrons? a.reactive metal b.nonreactive metal c.reactive nonmetal d.nonreactive nonmetal

11. 2.Which description applies to an element that has two valence electrons? a.reactive metal b.nonreactive metal c.reactive nonmetal d.nonreactive nonmetal

12. 3.How do sodium and chlorine both achieve stable electron configurations when they react? a.An electron is transferred from the sodium atom to the chlorine atom. b.An electron is transferred from the chlorine atom to the sodium atom. c.Both atoms gain one electron. d.Both atoms lose one electron.

13. 3.How do sodium and chlorine both achieve stable electron configurations when they react? a.An electron is transferred from the sodium atom to the chlorine atom. b.An electron is transferred from the chlorine atom to the sodium atom. c.Both atoms gain one electron. d.Both atoms lose one electron.

14. 4. The ratio of aluminum ions to chloride ions in aluminum chloride (AlCl 3 ) is 3:1. True False

15. 4.The ratio of aluminum ions to chloride ions in aluminum chloride (AlCl 3 ) is 3:1. True False Correct ratio is 1:3. There is 1 Aluminum atom to 3 Chlorine atoms.

16. Describing Ionic Compounds (part of 6.3) Binary Ionic Compounds are made from only two elements. Names of Ionic Compounds includes the cation (metal) followed by the anion (nonmetal) including the suffix -ide. – Example: Sodium Chloride The alkali metals, alkaline earth metals, and aluminum form ions with positive charges equal to the group number. – Examples: Potassium ion is K +, Calcium ion is Ca 2+, and Aluminum ion is Al 3+

18. Many transition metals form more than one type of ion. – Examples: Copper (I) ion looses 1 electron and forms 1+ charge Copper (II) ion looses 2 electrons and forms 2+ charge Ion name contains a Roman numeral to indicate the charge of the ion – Examples: Red copper (I) oxide’s formula is Cu 2 O Black copper (II) oxide’s formula is CuO

19. Writing Formulas for Ionic Compounds Symbol for cation is first, followed by anion Use subscripts to show the ration of ions in the compound. Charges of anion and cation must add up to zero because all compounds are neutral. Example: – Sodium Sulfide There must be two Na + for each S 2- Na 2 S

20. Covalent Bonding Chemical bond in which two atoms share a pair of valence electrons. Represented 4 ways:

21. Two or more atoms joined together by a covalent bond form a molecule. The molecule is held together as the shared electrons orbit both nuclei. Usually consist of two nonmetal elements Diatomic molecules are made up to 2 atoms.

22. Polar Covalent Bonds In some molecules, electrons may not be shared equally. As a result, one part of the molecule has more electrons and a negative charge. The other end of the molecule has a positive charge.

23. Nonpolar Molecule In a carbon dioxide (CO 2 ) molecule, the valence electrons are shared equally between the carbon atom and the oxygen atoms. The molecule has no charge because it is linear. Polar Molecule In a water (H 2 O) molecule, the molecule is bent. The electrons are not shared equally between the oxygen atom and the hydrogen atoms so the Oxygen end of the molecule is negative while the Hydrogen end of the molecule is positive.

24. Attraction between Polar Molecules The positive end of one water molecule is attracted to the negative end of another water molecule. In addition, ions (such as sodium chloride NaCl) can be attracted to these positive and negative charges of a water molecule.

25. Review 1.What attractions hold two atoms in a molecule together? a.attraction between ions with opposite charges b.attraction between the nuclei of the atoms and shared electrons c.attraction between each nucleus and the electrons of the other atom d.attraction between the molecule and other molecules

26. 1.What attractions hold two atoms in a molecule together? a.attraction between ions with opposite charges b.attraction between the nuclei of the atoms and shared electrons c.attraction between each nucleus and the electrons of the other atom d.attraction between the molecule and other molecules

27. 2.What determines whether a molecule is polar? a.type of atoms and shape of molecule b.mass of atoms and number of valence electrons c.type and mass of atoms d.ionization energy and number of covalent bonds

28. 2.What determines whether a molecule is polar? a.type of atoms and shape of molecule b.mass of atoms and number of valence electrons c.type and mass of atoms d.ionization energy and number of covalent bonds

29. Describing Molecular Compounds (part of 6.3) The name and formula of a molecular compound describe the type and number of atoms in the compound. Most metallic elements appear first in the name and formula. These elements are further to the left on the periodic table. If both elements are in the same group, the more metallic element is closer to the bottom of the group. The name ends with the suffix –ide. Example: Carbon Dioxide

30. When a molecule contains two of the same elements, Greek prefixes are used to describe the number of atoms of each element. Example: CO 2 is Carbon dioxide. N 2 O 4 is Dinitrogen tetraoxide.

31. Polyatomic Ions Some molecules, (a group of atoms that are covalently bonded) have positive or negative charge. The ammonium ion, includes one nitrogen atom and four hydrogen atoms, loses a valence electron as the molecule forms. This loss leaves only 10 electrons to balance the charge on 11 protons, so the ion has a positive charge. Some formulas include polyatomic ions Example: Iron (III) Hydroxide formula is Fe(OH) 3.

33. Review 1. Which of these formulas describes a binary ionic compound? a.O 2 b.MgCl 2 c.NO 2 d.Fe(OH) 3

34. 1. Which of these formulas describes a binary ionic compound? a.O 2 b.MgCl 2 c.NO 2 d.Fe(OH) 3

35. 2.What is the correct name for CCl 4 ? a.carbon(IV) chloride b.carbon tetrachlorine c.carbon tetrachloride d.monocarbon tetrachloride

36. 2.What is the correct name for CCl 4 ? a.carbon(IV) chloride b.carbon tetrachlorine c.carbon tetrachloride d.monocarbon tetrachloride