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.

Verified step by step guidance

1. Identify the second-row elements in the periodic table, which are: Li, Be, B, C, N, O, F, and Ne.
2. Recognize that binary hydrides are compounds formed between hydrogen and these elements.
3. Draw the Lewis electron-dot structures for each hydride:
4. LiH: Li has 1 valence electron, H has 1 valence electron. The structure is Li-H.
5. BeH2: Be has 2 valence electrons, H has 1 valence electron. The structure is H-Be-H.
6. BH3: B has 3 valence electrons, H has 1 valence electron. The structure is H-B-H with an additional H bonded to B.
7. 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.
8. 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.
9. H2O: O has 6 valence electrons, H has 1 valence electron. The structure is H-O-H with two lone pairs on O.
10. HF: F has 7 valence electrons, H has 1 valence electron. The structure is H-F with three lone pairs on F.
11. NeH: Ne has 8 valence electrons, H has 1 valence electron. Ne does not typically form stable hydrides due to its full valence shell.
12. 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.

Key Concepts

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.

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.

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.