Question

Predict the reactivity of each atom based on its electron configuration a. potassium b. fluorine c. neon

Short answer

Potassium has 1 valence electron and can easily lose it to achieve a stable electron configuration, making it highly reactive. Fluorine has 7 valence electrons and needs to gain 1 electron to achieve a noble gas configuration, making it highly reactive as well. Neon already has 8 valence electrons and a stable noble gas electron configuration, making it non-reactive and chemically inert.

Step-by-step solution

Identify the electron configurations

For each of the given atoms, we will first determine the electron configuration. This can be found using the periodic table by grouping electrons into shells and subshells. a. Potassium (K) - Atomic number: 19 Electron Configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ b. Fluorine (F) - Atomic number: 9 Electron Configuration: 1s² 2s² 2p⁵ c. Neon (Ne) - Atomic number: 10 Electron Configuration: 1s² 2s² 2p⁶

Analyze the valence electrons

Now, let's analyze the electron configurations and identify the number of valence electrons for each element. Valence electrons are the electrons in the outermost shell. a. Potassium - 4s¹ (1 valence electron) b. Fluorine - 2s² 2p⁵ (7 valence electrons) c. Neon - 2s² 2p⁶ (8 valence electrons)

Predict the reactivity based on electron configurations

Atoms tend to become more stable by achieving a noble gas electron configuration. They will either lose, gain, or share electrons to reach this configuration. In general, atoms with fewer valence electrons will lose electrons, atoms with more valence electrons will gain electrons, and those with a full valence shell will not react. a. Potassium - It has only 1 valence electron and can easily lose it to attain a stable electron configuration similar to a noble gas (argon). This makes potassium highly reactive. b. Fluorine - It has 7 valence electrons and needs to gain just 1 electron to achieve a stable noble gas electron configuration like neon. This makes fluorine highly reactive as well. c. Neon - It already has a complete outer electron shell with 8 valence electrons, which corresponds to a noble gas electron configuration. Thus, Neon is not reactive and is chemically inert. So, based on their electron configurations, potassium and fluorine are highly reactive, while neon is not reactive.

Key concepts

Electron Configuration

Understanding electron configuration is crucial when predicting an atom's reactivity. Atoms are built with a nucleus surrounded by electrons that arrange themselves in specific energy levels, or shells. These shells contain subshells designated s, p, d, and f. The configuration of these electrons follows a set of rules defined by quantum mechanics, prominently the Pauli Exclusion Principle and Hund’s Rule.

For instance, Potassium (K) with an atomic number of 19 has an electron configuration of 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹. The 'squared' numbers indicate paired electrons, while the '1' in 4s¹ shows an unpaired electron in the outermost shell. This outermost electron plays a key role in determining reactivity because it can be easily lost or gained during chemical reactions.

Valence Electrons

The valence electrons are those present in the outermost shell of an atom. They are significant as they determine an atom’s chemical properties and its ability to bond with other atoms. For example, Potassium has one valence electron in the 4s orbital, whereas Fluorine has seven valence electrons in the 2s and 2p orbitals. Neon, with eight valence electrons, has a complete outer shell.

Valence electrons are the 'currency' of chemical reactions. Atoms 'trade' these electrons through sharing, losing, or gaining to achieve a full outer shell, leading to chemically stable configurations similar to noble gases. In our exercise, knowing the number of valence electrons for various elements guides us in predicting their chemical reactivity.

Periodic Table Trends

The periodic table is more than a list of elements; it's a roadmap of chemical properties, including atomic reactivity. Certain trends emerge when looking at the periodic table. Reactivity in metals, found on the left side of the table, increases as we move down a group, while nonmetal reactivity decreases down a group. Across a period, metal reactivity decreases from left to right, and nonmetal reactivity increases, peaking with the halogens right before the noble gases.

Metallic and Nonmetallic Reactivity

Metals like potassium tend to lose electrons and react strongly, especially as their atomic size increases down a group. Nonmetals like fluorine tend to gain electrons and are very reactive at the top of a group. Inert gases like neon have filled valence shells, making them least reactive.

Chemical Reactivity

Chemical reactivity is the tendency of an element to engage in chemical reactions. Elements like potassium, with one valence electron, are eager to lose that electron to reach the stable, noble gas electron configuration and are thus highly reactive. Conversely, elements like fluorine are eager to gain one electron for stability and are also highly reactive.

On the other end of the spectrum, neon's filled valence shell means it's already stable and has little incentive to engage in chemical reactions. This results in neon being chemically inert. Understanding these principles allows us to predict an atom’s reactivity based on its position in the periodic table, electron configuration, and valence electron count.