1. 5-1 Notes - Compounds
Chapter 5, Lesson 1

2. Compounds
A compound is a pure substance that contains two or more different elements.
CO2
H2O
HCl O2

3. Compounds
A chemical formula is an ingredient list for a compound that uses symbols and subscripts.

4. Compounds formula – shows the ratio of elements in a molecule
formulas of familiar compounds:
Compound
Formula
Water
H2O
Carbon Dioxide
CO2
Carbon Monoxide CO
Methane
CH4
Ammonia
NH3
Table Sugar
C12H22O11
formula – shows the ratio of elements in a molecule
subscript – shows the number of atoms of an element in a molecule

5. Compounds
sucrose (sugar)
C12H22O11

6. Compounds and Elements
A compound has different properties than the elements that make it up.
The element Sodium (Na) is a soft metal and is DANGEROUS by itself.
The element Chlorine (Cl) is a greenish-yellow gas and is DEADLY by itself.
The compound Sodium chloride (NaCl) is table salt and you eat it all the time!

7. Lewis Dot Diagrams
The force that holds atoms together in a compound is called a chemical bond.
caffeine

8. Lewis Dot Diagrams
The electrons in an atom’s outside energy level are called valence electrons.

9. Lewis Dot Diagrams
Valence electrons are the only ones involved in forming bonds.
GROUP NUMBER
VALENCE NUMBER

10. Lewis Dot Diagrams
Lewis dot diagrams use symbols and dots to represent the valence electrons.
1A A A A A A A A

11. Lewis Dot Diagrams

12. Ionic Compounds
An ionic compound is when two or more elements or compounds gain or lose electrons and form ionic bonds.

13. Ionic Compounds
An ionic bond is an electrical attraction between positively and negatively charged ions.
Cl-
Na+

14. Another casualty in the War of the Atoms

15. Ionic Compounds
An atom can become charged by giving one or more electrons to another atom.
Both atoms become ions.

16. Ionic Compounds The positive ion is usually a metal (Lithium)
The negative ion is usually a non-metal (Fluorine)
positive ions
negative ions

17. Ionic Compounds
Lithium loses its 1 valence electron and becomes a positively charged ion (1+).
Fluorine gains the 1 valence electron and becomes a negatively charged ion (1-).

18. Ionic Compounds
The lithium ion (1+) and fluorine ion (1-) now have equal and opposite charges.
They are attracted to each other and form a compound: Lithium fluoride (LiF).

19. Ionic Compounds
Lithium fluoride is made only of 2 elements and known as a binary compound.

21. Ionic Compounds 1 1A 17 7A
Elements in the same column on the periodic table form a group.

22. Ionic Compounds 1 1A 17 7A
Atoms in Group 1 (1A) give up 1 electron to become 1+ ions. 1+

23. Ionic Compounds 1 1A 17 7A
Atoms in Group 17 (7A) need 1 electron and form 1- ions. 1-

24. Ionic Compounds 1 1A 17 7A
When a positive ion from Group 1 and a negative ion from Group 17 combine, a salt such as sodium chloride (NaCl) forms.

25. Ionic Compounds 2 2A 16 6A
Group 2 (2A) elements give up 2 electrons to form ions with a 2+ charge.
Group 16 (6A) elements need 2 electrons and form ions with a 2- charge.

26. Ionic Compound Properties
Usually solids at room temperature
Brittle and break apart easily
Have high melting and boiling points
Many dissolve in water and become good conductors of electricity (saltwater)

27. Noble Gases Elements in Group 18 are the noble gases.
Noble gases are stable because their outer energy levels are filled.
Stable elements rarely react to form compounds.

28. Gain Electrons to be Noble Gas
Chlorine can achieve noble gas structure by filling its outer energy levels.
Chlorine can become more stable by gaining one electron and forming the Chloride ion Cl–.

29. Gain Electrons to be Noble Gas
Chlorine WANTS
to be just like Argon, the Noble Gas
in its row.

30. Lose Electrons to be Noble Gas
Magnesium can achieve the electron structure of Neon, the nearest noble gas on the periodic table.
Magnesium can lose two electrons to form the stable ion Mg2+.

31. Lose Electrons to be Noble Gas
Magnesium WANTS to be just like Neon, the Noble Gas in its row.

32. Covalent Compounds
If an element needs to gain or lose too many electrons, it shares instead.
A covalent bond is a chemical bond formed when atoms share electrons.

33. Covalent Compounds Carbon has 4 valence electrons.
Too much energy is needed for carbon to easily gain or lose 4 electrons, so it shares.

34. Covalent Compounds
Elements that are close together on the periodic table are more likely to share electrons in a covalent bond than to transfer electrons (or atoms bonding with themselves).

35. Covalent Compounds
All organic compounds are covalent compounds based on carbon atoms.

36. Covalent Compounds

37. Ionic Compounds

38. Covalent Compound Properties
Can be solids, liquids, or gases at room temperature
Usually have lower melting and boiling points than ionic compounds
Do not usually separate in water
Most do not conduct electricity (sugar water)
Is called a molecule - a neutral particle that forms as a result of electron sharing

39. Covalent Compound Properties
The number of bonds an atom can form = the number of valence electrons needed to make a total of 8.

40. Covalent Compound Properties
H needs 1 valence electron, so it can make 1 bond.
C needs 4 valence electrons, so it can make 4 bonds.
N needs 3 valence electrons, so it can make 3 bonds.

41. Multiple Bonds Covalent bonds can consist of:
Single bonds (one pair of electrons shared)
Double bonds (two pairs of electrons shared - stronger than single bonds)
Triple bonds (three pairs of electrons shared - stronger than double bonds).

42. Multiple Bonds
The shared pair of electrons is a single covalent bond, which holds the hydrogen molecule H2 together.

43. Fail.

44. 5.1 How Atoms Form Compounds
Bromine is in Group 17. How many electrons does bromine need to gain or lose to obtain a noble gas structure?
A gain one electron
B gain two electrons
C lose one electron
D lose two electrons

45. Which element can form a negative ion? A carbon B magnesium C chlorine
5.1 How Atoms Form Compounds
Which element can form a negative ion?
A carbon
B magnesium
C chlorine
D lithium

46. What holds two elements together in an ionic bond?
5.1 How Atoms Form Compounds
What holds two elements together in an ionic bond?
A covalent bonds from shared electrons
B electron clouds combining
C unpaired electrons attracting each other
D opposite charges on negative and positive ions

47. How many dots are in a Lewis dot diagram for the Group 1 element lithium?
B 2
C 3
D 4

48. Why are noble gases unlikely to form compounds with other elements?
A They form ionic bonds.
B They have 8 valence electrons.
C They form covalent bonds.
D Their outer energy levels are not filled with electrons.

49. Compounds sharing electrons are held together by ____.
A ionic bonds
B covalent bonds
C metallic bonds
D polymer chains

50. Which elements are least likely to react with other elements? A metals
SCI 3.b
Which elements are least likely to react with other elements?
A metals
B Group 17 elements
C Group 16 elements
D Noble gases

51. SCI 3.b
In the ionic compound magnesium oxide (MgO), how many electrons did oxygen give magnesium?
A 1
B 2
C 3
D none of the above

52. Noble gases are in which group on the periodic table? A 1 B 2 C 17
SCI 3.f
Noble gases are in which group on the periodic table?
A 1
B 2
C 17
D 18

53. Investigating the Periodic Table 3:51

54. Formation of Chemical Bonds 2:42

55. How Can Police Use Chemistry to Help Solve Crimes? 1:32

56. 1944: Mysterious Balloon Launching 3:50