Lewis diagrams | Atoms, isotopes, and ions | High school chemistry | Khan Academy

Summary

In this video, the instructor introduces Lewis diagrams as a simplified way to visualize valence electrons in atoms, using nitrogen as an example. The Bohr model is reviewed, highlighting that nitrogen has seven electrons, with five being valence electrons. The video explains how to represent these valence electrons in a Lewis diagram, including the concept of ions. The instructor outlines a general pattern for determining the number of valence electrons based on the periodic table, particularly noting that groups 13-18 can be calculated by subtracting 10 from the group number.

Takeaways

• 😀 The video introduces Lewis diagrams as a way to visualize valence electrons in atoms.
• 😀 The Bohr model is reviewed, explaining that nitrogen has 7 electrons and 7 protons.
• 😀 In the Bohr model for nitrogen, the first shell contains 2 electrons, and the second shell holds 5 unpaired electrons.
• 😀 Valence electrons are the outermost electrons involved in chemical reactions, and they are key to understanding chemical behavior.
• 😀 Lewis diagrams simplify the depiction of valence electrons by showing only the outermost electrons, like nitrogen's 5 valence electrons.
• 😀 The nitride ion example shows that when nitrogen gains 3 electrons, it has 8 valence electrons and carries a negative three charge.
• 😀 The periodic table can help determine the number of valence electrons based on the group number of the element.
• 😀 For elements in Groups 13 through 18, you subtract 10 from the group number to find the number of valence electrons.
• 😀 Group 13 elements have 3 valence electrons, Group 14 have 4, Group 15 have 5, Group 16 have 6, Group 17 have 7, and Group 18 have 8.
• 😀 This approach helps simplify the understanding of how elements in the same group tend to share similar chemical properties due to their valence electron configurations.

Q & A

What are Lewis diagrams?

Lewis diagrams are simplified visualizations that depict the valence electrons of an atom using its elemental symbol.

How many protons and electrons does a neutral nitrogen atom have?

A neutral nitrogen atom has seven protons and, consequently, seven electrons.

What does a Bohr model for nitrogen look like?

In a Bohr model for nitrogen, the first shell contains two electrons, and the second shell contains five electrons, arranged with four unpaired and one paired.

What are valence electrons and why are they important?

Valence electrons are the electrons in the outermost shell of an atom, and they are significant because they are involved in chemical reactions.

How many valence electrons does a nitride ion have?

A nitride ion has eight valence electrons because it has gained three additional electrons.

What charge does a nitride ion have, and how is it represented?

A nitride ion has a negative three charge, represented with brackets around the Lewis diagram and the notation '3-'.

How can you determine the number of valence electrons for elements in the periodic table?

You can generally determine the number of valence electrons by looking at the group number of the element. For groups 1 and 2, it corresponds directly to the group number, while for groups 13 to 18, you subtract 10 from the group number.

What is the pattern for valence electrons in groups 1 and 2?

Elements in Group 1 have one valence electron, and elements in Group 2 have two valence electrons.

What are the valence electrons for groups 13 to 18?

Group 13 has three valence electrons, Group 14 has four, Group 15 has five, Group 16 has six, Group 17 has seven, and Group 18 has eight valence electrons.

Why do electrons tend to spread apart in their outer shell?

Electrons tend to spread apart in their outer shell because they prefer to minimize repulsion between each other, allowing for more stable arrangements.