Question

Of the metals Be, \(\mathrm{Mg}, \mathrm{Ca}\) and Sr of group 2 in the periodic table, the least ionic chloride will be formed \(\begin{aligned}&\text { by } \\\&\text { by } \mathrm{Ca} \text { (c) } \mathrm{Mg} & \text { (d) } \mathrm{Sr}\end{aligned}\) (a) Be (b) \(\mathrm{Ca}\)

Short answer

The least ionic chloride will be formed by Be (a), as it has the highest electronegativity in Group 2.

Step-by-step solution

Understanding Ionic Character

The ionic character of a compound depends on the difference in electronegativity between the two atoms forming the bond. The greater the difference, the more ionic the bond is.

Considering Electronegativity Trends

In a group of the periodic table, electronegativity decreases as we move down the group. Therefore, as we go from Be to Sr in Group 2, the electronegativity of the metal decreases.

Determining the Least Ionic Chloride

Because Be is at the top of Group 2, it will have the highest electronegativity compared to Mg, Ca, and Sr. This means that Be will form the least ionic chloride, as the electronegativity difference between Be and Cl will be the smallest.

Key concepts

Electronegativity

Electronegativity is a measure of an atom's ability to attract and hold onto electrons when it forms a chemical bond. The concept was introduced by Linus Pauling, and it plays a crucial role in determining the type and strength of bonding between atoms in compounds. In the context of ionic compounds, a high difference in electronegativity between two atoms will typically lead to the formation of an ionic bond because one atom will attract electrons much more strongly than the other, effectively 'taking' the electrons to become negatively charged, while the other atom becomes positively charged.

Understanding electronegativity is essential when predicting the formation and properties of chemical compounds. For example, in the exercise concerning the formation of chlorides with metals from Group 2 (Be, Mg, Ca, and Sr), the differing electronegativities of the metals help us predict which metal chloride will have the least ionic character. The metal with the higher electronegativity, in this case beryllium (Be), will have a smaller difference in electronegativity with chlorine (Cl), resulting in a bond with a lesser ionic character compared to the chlorides of the other metals mentioned.

Periodic Table Trends

The periodic table is not just a tool for classifying elements; it also shows trends in the properties of elements, including their size, ionization energy, and as highlighted in the exercise, electronegativity.

Understanding Group Trends

When examining elements within a group (a vertical column on the periodic table), certain properties change in a predictable way. For Group 2 elements, such as Be, Mg, Ca, and Sr, electronegativity decreases as we move down the group. The reason behind this trend lies in the increasing atomic radius and the additional electron shells that reduce the pull on valence electrons.

These trends help us solve problems like the one provided. Since the Group 2 metals’ electronegativity decreases down the group, the difference in electronegativity between each successive metal and chlorine increases, theoretically increasing the ionic character of the chlorides they form. This understanding is crucial for correctly identifying that beryllium chloride (BeCl\(_2\)) would be the least ionic chloride among the options given, because beryllium sits highest in the group.

Chemical Bonding

Chemical bonding is the force that holds atoms together in compounds. There are three primary types of chemical bonds: ionic, covalent, and metallic. Ionic bonds form between metals and non-metals when there is a large difference in electronegativity, resulting in the transfer of electrons from the metal to the non-metal, creating ions. Covalent bonds occur when two non-metals share electrons more or less equally, due to similar electronegativities.

The exercise deals with the formation of ionic compounds, specifically chlorides of Group 2 metals. These metals lose two electrons to form cations, and the non-metal chlorine gains one electron to form an anion. The electronegativity difference between the metal cations and chlorine anions dictates the degree of ionic character of the resulting compound. Applying this knowledge to the exercise, we understand why BeCl\(_2\) has the least ionic character because the electronegativity difference between beryllium and chlorine is the smallest among the given metals, hinting at a shift towards more covalent character in its bonding.