Question

Choose the element that fits each description: (a) the higher electronegativity \(\mathrm{Cl}\) or \(\mathrm{Br}\) (b) the higher first ionization energy \(O\) or \(S\) (c) the lower electronegativity Ca or \(C\)

Short answer

The element with the (a) higher electronegativity is \text{Cl}, (b) higher first ionization energy is \text{O}, and (c) lower electronegativity is \text{Ca}.

Step-by-step solution

Comparing Electronegativity of Halogens

Electronegativity is the ability of an atom to attract shared electrons in a covalent bond. To compare electronegativity between chlorine (Cl) and bromine (Br), remember that electronegativity decreases down a group on the periodic table. Since chlorine is above bromine in the halogen group, chlorine will have a higher electronegativity.

Comparing First Ionization Energy of Oxygen and Sulfur

First ionization energy is the energy required to remove the outermost electron. It generally increases across a period and decreases down a group. Since oxygen (O) is above sulfur (S) in the same group and is to the right in the period, oxygen will have a higher first ionization energy.

Comparing Electronegativity of Ca and C

To compare the electronegativity of calcium (Ca) with carbon (C), note that electronegativity increase across a period from left to right and decreases down a group. Carbon is to the right of calcium on the same period and thus, will have a higher electronegativity. Consequently, calcium will have the lower electronegativity.

Key concepts

Electronegativity

Understanding electronegativity is crucial when delving into chemical bonds and reactions. It represents how strongly an atom can attract and hold onto electrons when it is part of a compound.

Electronegativity increases from left to right across a period due to the increasing positive charge in the nucleus, which can more effectively pull electrons closer. In contrast, it decreases down a group because additional electron shells are added making the outer electrons more distant from the nucleus and less tightly held.

To grasp this concept with real elements, consider our comparison of chlorine (Cl) and bromine (Br), both members of the halogen family. Chlorine is higher up in the group, so it has a stronger pull on electrons, translating to higher electronegativity.

First Ionization Energy

The first ionization energy of an element is defined as the amount of energy required to remove the most loosely bound electron from an isolated gaseous atom to form a cation.

Just like electronegativity, the first ionization energy generally increases across a period as atoms hold electrons more tightly due to the increasing nuclear charge. Conversely, it decreases down a group since the outermost electrons are farther from the nucleus and feel a reduced positive charge.

Considering our exercise, oxygen (O) sits higher up and to the right compared to sulfur (S) in the same group, thus it has a higher first ionization energy.

Comparing Elements

When comparing elements, we use properties such as electronegativity and ionization energy to predict their behavior in chemical reactions. These properties are influenced by the structure of the periodic table. The position of an element can tell us about its reactivity, the types of bonds it will form, and its role in chemical reactions.

Through comparison, we can deduce that elements with higher electronegativity, like carbon (C) over calcium (Ca), are more likely to attract electrons to form negative ions or participate in more polar covalent bonds.

Halogens

The halogens form a fascinating group in the periodic table. Found in Group 17, they are one electron short of a full octet, which results in high reactivity, especially for those higher up in the group, such as fluorine and chlorine.

Halogens are known for their strong disinfectant properties and the ability to form salts when coupled with metals. Understanding their position in the periodic table can help predict properties like boiling point, electronegativity, and reactivity trends. For instance, as you go down the group from fluorine to iodine, these elements become less electronegative and more metallic in character.

Periodic Group

A periodic group is a vertical column in the periodic table and is also known as a family of elements. Each element in a group has the same number of valence electrons, which dictates similar chemical behavior amongst group members.

For example, all halogens have seven valence electrons, leading them to often participate in reactions that achieve a complete octet. Understanding the concept of periodic groups allows us to predict the properties of elements based on their known relatives in the same group.