Question

Using the periodic table, arrange the atoms in each set in order of increasing electronegativity. a. \(\mathrm{Li}, \mathrm{Na}, \mathrm{K}\) b. \(\mathrm{Na}, \mathrm{Cl}, \mathrm{P}\) c. Se, \(\mathrm{Ca}, \mathrm{O}\)

Short answer

a. \[K < Na < Li \] b. \[Na < P < Cl \] c. \[Ca < Se < O \]

Step-by-step solution

Understand Electronegativity

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

Arrange \(\text{Li, Na, K}\)

For the elements in group 1 (alkali metals): Lithium (Li), Sodium (Na), and Potassium (K), electronegativity increases as we move up the group. Therefore, the order of increasing electronegativity is \[K < Na < Li \].

Arrange \(\text{Na, Cl, P}\)

For the elements in period 3: Sodium (Na), Phosphorus (P), and Chlorine (Cl), electronegativity increases as we move from left to right across the period. Therefore, the order of increasing electronegativity is \[Na < P < Cl \].

Arrange \(\text{Se, Ca, O}\)

For Selenium (Se), Calcium (Ca), and Oxygen (O): Oxygen is in group 16 (high electronegativity), Selenium is also in group 16 but below Oxygen (lower electronegativity than Oxygen), and Calcium is in group 2 (low electronegativity). The order of increasing electronegativity is \[Ca < Se < O \].

Key concepts

Periodic Table

The periodic table is a tabular arrangement of chemical elements, organized by increasing atomic number. Each element's position reveals a lot about its properties. Elements are arranged in rows called periods and columns called groups. Elements in the same group often have similar chemical properties.

Periodic Trends

Periodic trends refer to the patterns observed in the periodic table that highlight changes in elemental properties. These include:
- Electronegativity
- Atomic radius
- Ionization energy
Understanding these trends is key to predicting elemental behavior. For example, electronegativity generally increases across a period (left to right) and decreases down a group (top to bottom).

Alkali Metals

Alkali metals make up Group 1 on the periodic table. They include Lithium (Li), Sodium (Na), Potassium (K), and others. Key features:
- Highly reactive, especially with water
- Soft and can be cut with a knife
- Have low electronegativity
Their reactivity increases down the group, while their electronegativity decreases.

Electronegativity Trends

Electronegativity is a measure of an atom's ability to attract electrons in a chemical bond. Important points to remember:
- Increases across a period (left to right).
- Decreases down a group (top to bottom).
For example, in Period 3, the order from lowest to highest electronegativity is Sodium (Na) < Phosphorus (P) < Chlorine (Cl). In Group 1, the order from lowest to highest is Potassium (K) < Sodium (Na) < Lithium (Li).

Group 1 Elements

Group 1 elements, also known as Alkali Metals, are known for their high reactivity. They react vigorously with water to form hydroxides and hydrogen gas. As you go down the group, the reactivity increases and electronegativity decreases. The elements in this group include:
- Lithium (Li)
- Sodium (Na)
- Potassium (K)
The order of increasing electronegativity is: Potassium (K) < Sodium (Na) < Lithium (Li).

Period 3 Elements

Period 3 elements include Sodium (Na), Magnesium (Mg), Aluminium (Al), Silicon (Si), Phosphorus (P), Sulfur (S), Chlorine (Cl), and Argon (Ar). Key points include:
- Electronegativity increases across the period from left to right.
- Sodium has the lowest electronegativity in this period, while Chlorine has the highest.
Thus, for electronegativity, the order in this set would be Sodium (Na) < Phosphorus (P) < Chlorine (Cl).