9.1.1 Valence Electrons and Chemical Bonding

Question 1

Valence Electrons and Chemical Bonding

Answer 1

• Chemical bonding involves sharing, donating, or gaining valence electrons.
• Lewis dot structures are a shorthand method for writing valence electron configurations.
• Elements usually react in set ratios to form neutral compounds so that each atom has a full octet.

Question 2

note

Answer 2

• Chemical bonding involves sharing, donating, or gaining valence electrons.
• Valence electrons are electrons beyond the previous
  noble gas core electron configuration. For example, the
  electron configuration of iron is 1s 2 2s 2 2p 6 3s 2 3p 6 3d 6 4s 2 . The 3d 6 and 4s 2 electrons in iron are beyond the argon core electron configuration, so the 3d 6 and 4s 2 electrons are valence electrons in iron.
• Lewis dot structures are a shorthand method for writing
  valence electron configurations.
• The atomic symbol (for example, O for oxygen) is written with one dot for each valence electron. Since oxygen has six valence electrons, six dots are included in the Lewis dot structure. For most elements, eight electrons give an especially stable configuration. This valence electron configuration is called an octet.
• Elements usually react in set ratios to form neutral compounds so that each atom has a full octet.
• For example, sodium and chlorine form an ionic bond when one electron from sodium transfers completely to chlorine. The result is a chloride ion with eight valence electrons (an octet), and a sodium ion with zero valence electrons (in effect, the previous shell has become the valence shell of sodium—so sodium has a full octet). The two ions form an ionic bond, and react in a one-to-one ratio to form an ionic compound.
• A covalent bond is formed by the sharing of electrons
  between two atoms. For example, two atoms of iodine react to form a molecule of diiodine. Two of the electrons are shared, so each atom effectively has eight valence electrons (an octet).

Question 3

Which one of the following compounds would you expect to be covalent?

Answer 3

OF2

Question 4

Which of the following is a reasonable Lewis Dot symbol for a fluorine atom?

Answer 4

-

Question 5

The electron configuration of Li + ion is 1s 2. How many valence electrons are found in the Li + ion?

Answer 5

none

Question 6

How many valence electrons are found in an atom of nitrogen?

Answer 6

5

Question 7

How many valence electrons does Na have?

Answer 7

1

Question 8

How many valence electrons does Na+ have?

Answer 8

0

Question 9

The electron configuration of an oxygen atom is 1s 22s 22p 4. How many valence electrons does an oxygen atom have?

Answer 9

6

Question 10

Which of the following is the correct Lewis dot structure for carbon dioxide?

Answer 10

A carbon atom has 4 valence electrons and an oxygen atom has 6 valence electrons. Therefore, a compound composed of one carbon atom and two oxygen atoms should have a total of 16 valence electrons(4 from C and 2 × 6 = 12 from O). In a Lewis Dot structure, those atoms need to be placed in such a way that each atom of a covalent compound has 8 valence electrons surrounding it.

Question 11

The electron configuration for sulfur is 1s 22s 22p 63s 23p 4. How many valence electrons does a sulfur atom have?

Answer 11

6

Question 12

Which of the following best represents the Lewis Dot structure of nitrogen?

Answer 12

A nitrogen atom has 5 valence electrons. The best depiction of these 5 electrons shows that the two 2s electrons are paired and the three 2p electrons are unpaired.