Chemistry. Unit 5 Review Part 1

Transcription

1 Chemistry Unit 5 Review Part 1

2 Molecules & Compounds 1. What are elements made of? 2. What are compounds made of? 3. What is a pure substance? 4. Why does a pure substance obey the Law of Definite ProporHons? 5. Draw the Lewis dot structure for silicon. 6. Draw the Lewis dot structure for stronhum. 7. How do atoms become more stable? 8. Why are only valence electrons involved in determining an atom s stability? 9. Phosphorous gains electrons or loses electrons to have a full shell of valence electrons.

3 Molecules & Compounds 1. What are elements made of? An element is made up of atoms that have the same number of protons and electrons, but may have a different number of neutrons.

4 Molecules & Compounds 1. What are elements made of? An element is made up of atoms that have the same number of protons and electrons, but may have a different number of neutrons. 2. What are compounds made of? A compound is made up of one or more types of atoms bonded together. For a given compound, the elements are always present in the same mass raho.

5 Molecules & Compounds 1. What are elements made of? An element is made up of atoms that have the same number of protons and electrons, but may have a different number of neutrons. 2. What are compounds made of? A compound is made up of one or more types of atoms bonded together. For a given compound, the elements are always present in the same mass raho. 3. What is a pure substance? A pure substance is made of only one type of element or one type of compound.

6 Molecules & Compounds 4. Why does a pure substance obey the Law of Definite ProporHons? The Law of Definite ProporHons states that a compound will always contain the same elements in exactly the same proporhons by mass. Since a pure substance is made of one type of element or compound, it s elements will always be present in the proporhons by mass.

7 Molecules & Compounds 5. Draw the Lewis dot structure for silicon.

8 Molecules & Compounds 5. Draw the Lewis dot structure for silicon. 6. Draw the Lewis dot structure for stronhum.

9 Molecules & Compounds 7. How do atoms become more stable? Atoms become more stable by having a full shell of valance electrons.

10 Molecules & Compounds 7. How do atoms become more stable? Atoms become more stable by having a full shell of valance electrons. 8. Why are only valence electrons involved in determining an atom s stability? Valence electrons are the only electrons involved because they are the outermost electrons in the cloud and are the ones that can be shared with or transferred to other atoms.

11 Molecules & Compounds 7. How do atoms become more stable? Atoms become more stable by having a full shell of valance electrons. 8. Why are only valence electrons involved in determining an atom s stability? Valence electrons are the only electrons involved because they are the outermost electrons in the cloud and are the ones that can be shared with or transferred to other atoms. 9. Phosphorous gains 3 electrons or loses 5 electrons to have a full shell of valence electrons.

12 Chemical Bonds 10. Why do atoms combine to form chemical compounds? 11. What is a molecular compound? 12. What is an ionic compound? 13. Describe a non- polar covalent bond. 14. Describe a polar covalent bond. 15. Describe an ionic bond. 16. Describe a metallic bond. 17. Why does a molecular formula represent the actual structure of a covalent compound? 18. Why does an ionic formula not represent the actual structure of an ionic compound? 19. Why does CS 2 have less ionic character than H 2 O, NaCl or CH 4?

13 Chemical Compounds 10. Why do atoms combine to form chemical compounds? Atoms combine to form chemical compounds in order to have a full shell of valence electrons and become more stable.

14 Chemical Compounds 10. Why do atoms combine to form chemical compounds? Atoms combine to form chemical compounds in order to have a full shell of valence electrons and become more stable. 11. What is a molecular compound? A molecular compound consists of two or more atoms held together by covalent bonds.

15 Chemical Compounds 10. Why do atoms combine to form chemical compounds? Atoms combine to form chemical compounds in order to have a full shell of valence electrons and become more stable. 11. What is a molecular compound? A molecular compound consists of two or more atoms held together by covalent bonds. 12. What is an ionic compound? An ionic compound consists of two or more ions held together by ionic bonds.

16 Chemical Compounds 13. Describe a non- polar covalent bond. A non- polar covalent bond joins two atoms together through the equal sharing of electrons.

17 Chemical Compounds 13. Describe a non- polar covalent bond. A non- polar covalent bond joins two atoms together through the equal sharing of electrons. 14. Describe a polar covalent bond. A polar covalent bond joins two atoms together through the unequal sharing of electrons.

18 Chemical Compounds 13. Describe a non- polar covalent bond. A non- polar covalent bond joins two atoms together through the equal sharing of electrons. 14. Describe a polar covalent bond. A polar covalent bond joins two atoms together through the unequal sharing of electrons. 15. Describe an ionic bond. An ionic bond creates ions by transferring an electron(s) from one atom to another atom, which creates an electrostahc abrachon between the two ions.

19 Chemical Compounds 13. Describe a non- polar covalent bond. A non- polar covalent bond joins two atoms together through the equal sharing of electrons. 14. Describe a polar covalent bond. A polar covalent bond joins two atoms together through the unequal sharing of electrons. 15. Describe an ionic bond. An ionic bond creates ions by transferring an electron(s) from one atom to another atom, which creates an electrostahc abrachon between the two ions. 16. Describe a metallic bond. A metallic bond joins atoms of the same type of metal by sharing valence electrons among all the nuclei (cahons).

20 Chemical Compounds 17. Why does a molecular formula represent the actual structure of a covalent compound? Covalent compounds exist as individual molecules. Each molecule contains the exact type and number of atoms specified in the molecular formula.

21 Chemical Compounds 17. Why does a molecular formula represent the actual structure of a covalent compound? Covalent compounds exist as individual molecules. Each molecule contains the exact type and number of atoms specified in the molecular formula. 18. Why does an ionic formula not represent the actual structure of an ionic compound? Ionic compounds do not exist as individual molecules, instead they exist in an elaborate laece structure. While the ionic formula specifies the exact raho of ions in the laece structure it does not specify the exact number of each ion present in the laece structure.

22 Chemical Compounds 19. Why does CS 2 have less ionic character than H 2 O, NaCl or CH 4? Carbon disulfide, CS 2, has less ionic character because the electronegahvity of carbon and sulfur is the same, 2.1. All the other compounds have bonds between atoms with different electronegahvihes.

23 Visual Models & Molecular Shapes 20. Why do lone pairs and bonds around the central atom determine a molecules shape? 21. Draw the Lewis dot structure for SO 3, including resonance structures that may exist. For each compound or polyatomic ion: 1) draw the Lewis dot structure, 2) use the ball and s;ck model to draw the shape of the electron arrangement, 3) name the shape of the electron arrangement, 4) use the structural formula model to draw the shape of the molecule, and 5) name the shape of the molecule. 22. Carbon dichloride dibromide, CCl 2 Br Nitrogen trifluoride, NF 3.

24 Visual Models & Molecular Shapes 20. Why do lone pairs and bonds around the central atom determine a molecules shape? Both lone pairs and bonds are made of electrons. These negahvely charged electron groups around the central atom want to get as far away from each other as possible because like charges repel each other.

25 Visual Models & Molecular Shapes 20. Why do lone pairs and bonds around the central atom determine a molecules shape? Both lone pairs and bonds are made of electrons. These negahvely charged electron groups around the central atom want to get as far away from each other as possible because like charges repel each other. 21. Draw the Lewis dot structure for SO 3, including resonance structures that may exist.

26 Visual Models & Molecular Shapes 22. Carbon dichloride dibromide, CCl 2 Br 2.

27 Visual Models & Molecular Shapes 22. Carbon dichloride dibromide, CCl 2 Br Nitrogen trifluoride, NF 3.