Question

For each of the following pairs of elements, identify which element would be expected to be more electronegative. It should not be necessary to look at a table of actual electronegativity values. a. Be or Ba b. \(\mathrm{N}\) or \(\mathrm{P}\) c. F or Cl

Short answer

For each pair of elements, the more electronegative element is: a. Be (beryllium) as electronegativity decreases from top to bottom within a group. b. N (nitrogen) for the same reason as above. c. F (fluorine), again due to the decrease in electronegativity from top to bottom within a group.

Step-by-step solution

Pair a: Be or Ba

Comparing beryllium (Be) and barium (Ba), we see that they both belong to Group 2 (alkaline earth metals) in the periodic table. Beryllium is in the second period while barium is in the sixth period. As electronegativity decreases from top to bottom within a group, Be is expected to be more electronegative than Ba.

Pair b: N or P

Comparing nitrogen (N) and phosphorus (P), both of these elements are in Group 15 (pnictogens) in the periodic table. Nitrogen is in the second period, while phosphorus is in the third period. Since electronegativity decreases from top to bottom within a group, nitrogen is expected to be more electronegative than phosphorus.

Pair c: F or Cl

Comparing fluorine (F) and chlorine (Cl), both of these elements are in Group 17 (halogens) in the periodic table. Fluorine is in the second period, while chlorine is in the third period. As electronegativity decreases from top to bottom within a group, fluorine is expected to be more electronegative than chlorine.

Key concepts

Periodic Table

The periodic table is a powerful tool in chemistry that organizes all known chemical elements in an informative grid. This arrangement is based on atomic number, electron configurations, and recurring chemical properties.
The rows of the periodic table are called periods, while the columns are known as groups or families. Each period consists of elements that have the same number of electron shells, but gradually increase in atomic number from left to right.
Meanwhile, elements in the same group share the same number of valence electrons, which gives them similar chemical properties. For example, Group 17 (halogens) includes elements such as fluorine and chlorine, known for their high reactivity.

• The periodic table helps predict the chemical behavior of elements.
• It’s a visual representation that reveals trends such as electronegativity and ionization energy.
• Understanding it is crucial for analyzing various chemical reactions and properties.

Chemical Elements

Chemical elements are pure substances consisting of only one type of atom, defined by their atomic number. This makes each element unique, reflecting properties specific to its atomic structure. Elements are the building blocks of all matter, arranged in the periodic table based on increasing atomic number.
Chemical elements can be metals, nonmetals, or metalloids, each with distinct sets of characteristics. For instance, metals like barium ( Ba ) are typically malleable and good conductors of heat and electricity, whereas nonmetals like nitrogen ( N ) usually lack theses properties.
On the periodic table, the placement of these elements provides insights into their chemical and physical behaviors, as well as their interactions with other elements.

• There are 118 recognized elements, each with unique properties.
• They're classified into categories like metals, nonmetals, and metalloids based on properties.
• The arrangement in the periodic table aids in predicting their interactions and behaviors.

Trends in Electronegativity

Electronegativity refers to the ability of an atom to attract and hold electrons. It is a crucial property in understanding how elements interact in chemical bonds.
Generally, electronegativity increases across a period (from left to right) and decreases down a group (from top to bottom) on the periodic table. This trend is because of the increasing positive charge in the nucleus across a period and the increasing distance of the valence electrons from the nucleus down a group.
For example, among the given pairs in the exercise, beryllium ( Be ) is more electronegative than barium ( Ba ) due to its higher position in Group 2. Similarly, nitrogen ( N ) and fluorine ( F ), being higher in periods compared to phosphorus ( P ) and chlorine ( Cl ) respectively, have higher electronegativities.

• Electronegativity helps predict molecule polarity and bond strength.
• Higher electronegativity means a stronger pull on shared electrons.
• This trend impacts the chemical reactivity and properties of elements.