Problem 43 - Chemistry: Principles and Reactions

Question

Give the symbols of (a) all the elements in period 2 whose atoms have empty \(2 \mathrm{p}\) orbitals. (b) all the metals in period 3 that have at least one unpaired electron. (c) all the alkaline earth metals that have filled \(3 \mathrm{~d}\) sublevels. (d) all the halogens that have unpaired \(4 p\) electrons.

Step-by-Step Solution

Answer

Question: Identify the following elements based on their electron configurations or positions in the Periodic Table: (a) Elements in Period 2 with empty 2p orbitals. (b) Metals in Period 3 with unpaired electrons. (c) Alkaline Earth Metals with filled 3d sublevels. (d) Halogens with unpaired 4p electrons. Answer: (a) Lithium (Li) and Beryllium (Be) (b) Sodium (Na) and Aluminum (Al) (c) None (d) Bromine (Br)

Step 1: (a) Elements in Period 2 with empty 2p orbitals.

To solve this part, we should focus on the elements that are in period 2 of the Periodic Table. In period 2, there are 8 elements: Lithium (Li), Beryllium (Be), Boron (B), Carbon (C), Nitrogen (N), Oxygen (O), Fluorine (F), and Neon (Ne). We know that 2p orbitals start filling after the 2s orbital is full. So, we need to find the elements whose 2s orbitals are full but 2p orbitals are empty. According to the electron configurations, both Lithium (Li) and Beryllium (Be) meet this criterion. Answer: Lithium (Li) and Beryllium (Be)

Step 2: (b) Metals in Period 3 with unpaired electrons.

To solve this part, let's look at the elements in period 3, which has 8 elements: Sodium (Na), Magnesium (Mg), Aluminum (Al), Silicon (Si), Phosphorus (P), Sulfur (S), Chlorine (Cl), and Argon (Ar). Out of these, Sodium (Na), Magnesium (Mg), and Aluminum (Al) are metals. We need to find out which of these have at least one unpaired electron. The electron configurations of these metals are as follows: Na (2,8,1), Mg (2,8,2), and Al (2,8,3). We can see that Sodium (Na) and Aluminum (Al) have unpaired electrons in their 3s and 3p orbitals, respectively. Answer: Sodium (Na) and Aluminum (Al)

Step 3: (c) Alkaline Earth Metals with filled 3d sublevels.

The alkaline earth metals are the elements in group 2 of the Periodic Table, which include Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba), and Radium (Ra). We need to determine which of these have filled 3d sublevels. The 3d sublevel can accommodate a maximum of 10 electrons, so we are looking for an element with a 3d10 configuration. None of the alkaline earth metals have a filled 3d sublevel because they have a maximum of 2 electrons in their outermost shell (their valence shell) and do not have any electrons in the d orbitals. Answer: None

Step 4: (d) Halogens with unpaired 4p electrons.

Halogens are elements in group 17 of the Periodic Table, which include Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I), and Astatine (At). We need to find the halogens that have unpaired 4p electrons. Let's analyze their electron configurations. Fluorine (F) has a 2p configuration, Chlorine (Cl) has 3p, Bromine (Br) has 4p, Iodine (I) has 5p, and Astatine (At) has a 6p configuration. Out of these, only Bromine (Br) has 4p electrons, and there is one unpaired electron in the 4p sublevel of Bromine's electron configuration (4s2, 3d10, 4p5). Answer: Bromine (Br)

Key Concepts

Electron Configuration

Electron configuration describes how electrons are distributed in an atom's orbitals. Understanding this concept is essential for predicting an element's chemical properties and reactivity. Each electron in an atom occupies the lowest energy level available, progressing from lower to higher energy sublevels as more electrons are added.

• The orbitals are arranged as s, p, d, and f, with s being the smallest and f the largest.
• For example, the electron configuration of Helium (He) is 1s², denoting two electrons in the first s orbital.
• When writing electron configurations, we fill the 1s orbital first, then the 2s, followed by 2p, and so on.

This systematic approach helps identify the location of unpaired electrons, an essential aspect when determining reactivity and bonding.

Unpaired Electrons

Unpaired electrons are electrons that do not have a pair in an atom's orbital. These electrons play a crucial role in chemical reactivity and magnetic properties of elements.

• Elements with unpaired electrons are often more reactive, as these electrons can easily engage in chemical bonds.
• Unpaired electrons can influence magnetic properties; for instance, they can contribute to paramagnetism, where materials are attracted by external magnetic fields.
• In the periodic table, identifying unpaired electrons helps predict which metals will readily participate in chemical reactions, like Sodium (Na) and Aluminum (Al) from Period 3, which both have unpaired electrons.

By examining the electron configuration, it can be seen whether an atom has unpaired electrons, indicating potential for reactivity and bonding.

Alkaline Earth Metals

Alkaline earth metals are located in Group 2 of the periodic table and include Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba), and Radium (Ra). These metals share common properties that are related to their electron configuration.

• They typically have two electrons in their outermost s orbital, making their general electron configuration expression ([noble gas]ns²).
• Their chemistry is dominated by the loss of these two valence electrons, leading to a +2 oxidation state in compounds.
• While they participate in the formation of compounds, none of these elements have filled 3d sublevels, as shown by their electron configurations.

This absence of filled 3d sublevels sets them apart from other metals and impacts their reactivity and bonding potential.

Halogens

Halogens are part of Group 17 in the periodic table, consisting of Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I), and Astatine (At). These elements are highly reactive non-metals with distinct electron configurations.

• Halogens typically possess seven electrons in their outer p orbitals, making them one electron short of a full octet. This results in a high tendency to gain electrons in reactions.
• The uneven electron configuration often includes unpaired p electrons, as seen with Bromine (Br), which has 4p electrons with one unpaired electron.
• The presence of unpaired electrons contributes to their high reactivity and ability to form negative ions.

The unique electron arrangements of halogens influence their ability to form compounds, particularly their affinity for forming salts with metals.