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Ch.22 - The Main Group Elements
McMurry - Chemistry 8th Edition
McMurry8th EditionChemistryISBN: 9781292336145Not the one you use?Change textbook
All textbooksMcMurry 8th EditionCh.22 - The Main Group ElementsProblem 22.22b
Chapter 22, Problem 22.22b

The following models represent the structures of binary hydrides of second-row elements:
b. Draw an electron-dot structure for each hydride. For which hydride is there a problem in drawing the structure? Explain.

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1
Identify the second-row elements in the periodic table, which are: Li, Be, B, C, N, O, F, and Ne.
Recognize that binary hydrides are compounds formed between hydrogen and these elements.
Draw the Lewis electron-dot structures for each hydride:
LiH: Li has 1 valence electron, H has 1 valence electron. The structure is Li-H.
BeH2: Be has 2 valence electrons, H has 1 valence electron. The structure is H-Be-H.
BH3: B has 3 valence electrons, H has 1 valence electron. The structure is H-B-H with an additional H bonded to B.
CH4: C has 4 valence electrons, H has 1 valence electron. The structure is H-C-H with two additional H atoms bonded to C.
NH3: N has 5 valence electrons, H has 1 valence electron. The structure is H-N-H with an additional H bonded to N and a lone pair on N.
H2O: O has 6 valence electrons, H has 1 valence electron. The structure is H-O-H with two lone pairs on O.
HF: F has 7 valence electrons, H has 1 valence electron. The structure is H-F with three lone pairs on F.
NeH: Ne has 8 valence electrons, H has 1 valence electron. Ne does not typically form stable hydrides due to its full valence shell.
Explain that the problem arises with NeH, as neon is a noble gas with a complete octet, making it unlikely to form a stable hydride.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Electron-Dot Structures

Electron-dot structures, also known as Lewis structures, represent the valence electrons of atoms within a molecule. In these diagrams, dots are used to indicate the presence of valence electrons, and lines represent bonds between atoms. Understanding how to draw these structures is essential for visualizing molecular geometry and predicting reactivity.
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Lewis Dot Structures: Ions

Binary Hydrides

Binary hydrides are compounds formed between hydrogen and another element, typically from groups 1, 2, or 13 of the periodic table. The properties and bonding characteristics of these hydrides can vary significantly based on the electronegativity and atomic size of the second-row element involved. Recognizing these differences is crucial for accurately drawing their electron-dot structures.
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Octet Rule and Exceptions

The octet rule states that atoms tend to form bonds in such a way that they each have eight electrons in their valence shell, achieving a stable electron configuration. However, some elements, particularly those in the second row like boron and hydrogen, can have fewer than eight electrons in their structures, leading to exceptions. Understanding these exceptions is vital for correctly identifying potential problems in drawing electron-dot structures for certain hydrides.
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Related Practice
Textbook Question

The following pictures represent structures of the hydrides of four second-row elements:

(1)

(2)

(3)

(4)

(b) Which compound has the lowest boiling point?

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Textbook Question

Look at the location of elements A, B, C, and D in the following periodic table:

Which hydride has the lowest boiling point?

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Textbook Question

Select the group 4A element that best fits each of the following descriptions.

b. Is the least dense semimetal

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Textbook Question

Which compound in each of the following pairs is more ionic?

(b) P4O6 or Ga2O3

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Textbook Question

In the following pictures of binary hydrides, ivory spheres

represent H atoms or ions, and burgundy spheres represent

atoms or ions of the other element.

(1)

(2)

(3)

(4)

(b) What is the oxidation state of hydrogen in compounds (1), (2), and (3)? What is the oxidation state of the other

element?

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Textbook Question

Look at the location of elements A, B, C, and D in the following periodic table:


(b) Classify each oxide as basic, acidic, or amphoteric.

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