Question

Using the periodic table only, arrange the elements in each set in order of decreasing EN: (a) \(\mathrm{N}, \mathrm{P}, \mathrm{Si}\) (b) \(\mathrm{Ca}, \mathrm{Ga},\) As

Short answer

(a) N > P > Si (b) As > Ga > Ca

Step-by-step solution

Understand Electronegativity (EN)

Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons. On the periodic table, EN generally increases from left to right across a period and decreases from top to bottom within a group.

Locate the Elements on the Periodic Table (Set A)

Locate nitrogen (N), phosphorus (P), and silicon (Si) on the periodic table. Nitrogen (N) is in period 2, group 15. Phosphorus (P) is in period 3, group 15. Silicon (Si) is in period 3, group 14.

Compare Electronegativity Values (Set A)

According to their positions: - Nitrogen (N) has the highest EN because it is in the second period and group 15. - Phosphorus (P) follows as it is in the same group but a period lower.- Silicon (Si) has the lowest EN because it is in group 14.

Arrange Elements in Decreasing EN (Set A)

Order for set A: - \(\text{N} > \text{P} > \text{Si}\)

Locate the Elements on the Periodic Table (Set B)

Locate calcium (Ca), gallium (Ga), and arsenic (As) on the periodic table. Calcium (Ca) is in period 4, group 2. Gallium (Ga) is in period 4, group 13. Arsenic (As) is in period 4, group 15.

Compare Electronegativity Values (Set B)

According to their positions: - Arsenic (As) has the highest EN because it is in group 15. - Gallium (Ga) follows as it is in group 13.- Calcium (Ca) has the lowest EN because it is in group 2.

Arrange Elements in Decreasing EN (Set B)

Order for set B: - \(\text{As} > \text{Ga} > \text{Ca}\)

Key concepts

Periodic Table

The periodic table is a systematic arrangement of all known chemical elements, organized by increasing atomic number (number of protons). It helps chemists understand patterns and relationships among elements. Each row is called a period and each column is a group. Elements in the same group have similar chemical properties because they have the same number of valence electrons. For example, Group 1 contains highly reactive alkali metals, and Group 18 consists of noble gases, which are mostly inert. This arrangement allows us to make predictions about the properties of elements based on their position.

Electronegativity

Electronegativity (EN) is a measure of an atom's ability to attract and bond with electrons. It plays a crucial role in determining the behavior of atoms in chemical reactions. The periodic table shows a clear trend in electronegativity:

• EN increases as you move from left to right across a period. This is because atoms have more protons, creating a stronger positive charge that pulls electrons closer.
• EN decreases as you move down a group because additional electron shells reduce the pull on valence electrons by increasing the distance from the nucleus.

For instance, fluorine has the highest EN because it is at the top right, while francium has one of the lowest EN values because it is at the bottom left.

Element Arrangement

When asked to arrange elements in order of decreasing electronegativity, the periodic table helps identify each element's position and compare their values.
Consider Set A: Nitrogen (N), Phosphorus (P), and Silicon (Si). Nitrogen, being in Period 2 and Group 15, has the highest EN. Phosphorus, in a lower period but the same group, follows. Silicon, in a different group with overall lower EN, comes last. Hence, the order is: N > P > Si.
In Set B: Calcium (Ca), Gallium (Ga), and Arsenic (As), Arsenic is highest in EN because it is in Group 15. Gallium, in Group 13, has a moderate EN. Calcium, in Group 2, has the lowest EN. Thus, the order is: As > Ga > Ca.