Question

Draw electron dot structures for the following elements: \(\mathrm{Na}, \mathrm{Al}, \mathrm{P}, \mathrm{Cl}\), and Ar. Which are most chemically reactive? Which are least chemically reactive?

Short answer

Most chemically reactive: Na and Al. Least chemically reactive: Ar.

Step-by-step solution

Writing the Electron Configurations

First, determine the number of valence electrons for each element based on their group number in the periodic table. Sodium (Na) is in group 1 and has 1 valence electron. Aluminum (Al) is in group 13 and has 3 valence electrons. Phosphorus (P) is in group 15 and has 5 valence electrons. Chlorine (Cl) is in group 17 and has 7 valence electrons. Argon (Ar) is in group 18 and has 8 valence electrons.

Drawing the Electron Dot Structures

Using the Lewis dot structure representation, arrange the valence electrons around each element's symbol. For Na, place one dot around the symbol. For Al, place three dots around the symbol, spaced to minimize repulsion. For P, place five dots around the symbol with at most two in any position. For Cl, place seven dots around the symbol, with at most two in any position except one. For Ar, place eight dots around the symbol, with two in each position.

Determine Chemical Reactivity

The chemical reactivity of elements is generally determined by the ease with which they can gain or lose electrons to achieve a stable octet. Elements with 1, 2, or 3 valence electrons tend to lose them and are more reactive (metals), while elements with 5, 6, or 7 valence electrons tend to gain electrons and are also more reactive (nonmetals). Noble gases, like Ar with a complete octet, are the least reactive.

Identifying Most and Least Chemically Reactive Elements

Na and Al are most chemically reactive due to their fewer number of valence electrons, which makes them likely to lose electrons and form cations. Conversely, Ar is the least chemically reactive because it already has a stable octet and generally does not form bonds.

Key concepts

Valence Electrons

Valence electrons play a pivotal role in understanding chemical behavior, as they are the outermost electrons of an atom and participate in chemical bonding. Think of them like the hands of an atom; they're what atoms use to 'hold onto' other atoms. In the periodic table, the group number can help us determine the number of valence electrons for the main-group elements. For instance, Sodium (Na), being in group 1, has 1 valence electron, whereas Aluminum (Al), in group 13, has 3 valence electrons.

These valence electrons are influential in dictating an element's reactivity because they are the ones lost, gained, or shared during chemical reactions. An element such as Phosphorus (P) has 5 valence electrons, and thereby seeks to gain or share three more to achieve a stable configuration of eight electrons, termed an octet. Therefore, when solving problems related to chemical reactivity, always start by examining the valence electrons; they’ll guide you to predict how an atom is likely to behave in a chemical reaction.

Chemical Reactivity

Chemical reactivity is an expression of how readily an element will undergo a chemical reaction. Imagine a dance floor where atoms are the dancers. Some are eager to pair up and dance (react), while others are content just to watch (unreactive). In the world of chemistry, elements like Sodium (Na) and Aluminum (Al) are the eager dancers. They want to lose their valence electrons to others, willing to form cations just to reach the stability of a full octet.

Periodic Trends and Reactivity

Across the periodic table, reactivity is not random; it follows trends. Metals located on the left side have 1 to 3 valence electrons and generally want to give them away, making them highly reactive. Nonmetals, on the other hand, usually want to gain electrons to fill their valence shell, especially those with 5 to 7 valence electrons, making them reactive as well. Elements with a full octet, like noble gases (e.g., Argon (Ar)), are quite content and hence least reactive. They’ve got a full dance card and are not looking for more partners.

Lewis Dot Structures

Lewis dot structures are like the atom’s ID photo; they show the most distinctive feature, the valence electrons. These simple diagrams are a handy tool for visualizing the valence electrons as dots around the symbol of an element. It's important to draw them correctly to understand how atoms bond in molecules. For example, Chlorine (Cl) has seven valence electrons, so we draw seven dots around its symbol, with a maximum pairing of two electrons per position.

Drawing Correctly Matters

When it comes to drawing Lewis dot structures, the goal is to represent the actual electron arrangement. Remember, having too many dots or placing them incorrectly could be like showing up with a fake ID to the atom’s party – it just doesn't work. Moreover, correctly drawn structures are crucial for predicting how atoms come together to form molecules. Whether it's a single dot for Sodium (Na) or a complete octet for Argon (Ar), every dot can influence the stability and reactivity of an atom.