Question

The element lawrencium is unstable and radioactive. Use the periodic table to predict the chemical formula for lawrencium chloride, given the formula of lutetium chloride, \(\mathrm{LuCl}_{3}\).

Short answer

The chemical formula for lawrencium chloride is \( \text{LrCl}_3 \).

Step-by-step solution

Identify Lutetium's Group

Lutetium (Lu) is a lanthanide in the periodic table, which means it belongs to Group 3 of the transition metals. Elements in this group typically form similar ions.

Examine Lawrencium's Position

Lawrencium (Lr) is found in the same group as lutetium but is slightly heavier, being the last element of the actinide series. Like lutetium, it is expected to form stable +3 ions due to its position in the periodic table.

Predict Lr Ion Charge

Since both lutetium and lawrencium are in Group 3, we predict that lawrencium, like lutetium, forms a stable ion with a +3 charge: \[ \text{Lr}^{3+} \].

Write the Chemical Formula

To achieve electrically neutral balance with the chloride ion \( \text{Cl}^- \), three chloride ions are needed to balance the +3 charge on the lawrencium ion. Thus, the chemical formula for lawrencium chloride is \( \text{LrCl}_3 \).

Key concepts

Radioactive Elements

Radioactive elements, like lawrencium, are known for their instability and ability to emit radiation as they decay into other elements. These elements are typically found beyond uranium on the periodic table and are characterized by having high atomic numbers.

Radioactivity occurs because their atomic nuclei are unstable. As a result, the nuclei release energy by emitting particles or electromagnetic waves. This process continues until they become more stable, often transmuting into different elements altogether. Most radioactive elements are man-made, synthesized in laboratories.

A key aspect of handling these elements is considering their half-life, which is the time it takes for half of the sample to decay. Half-life periods can range from fractions of a second to millions of years depending on the element.

• Understanding radioactivity is crucial for fields like nuclear medicine, energy, and forensic science.
• Proper safety measures are essential due to the hazardous nature of radiation.

Lanthanides and Actinides

The lanthanides and actinides are two series of elements in the periodic table. They are known as the f-block elements because they result from filling the 4f and 5f electron subshells, respectively.

**Lanthanides:** Lanthanides are sometimes referred to as rare earth elements, and they exhibit unique magnetic and luminescent properties. These elements are typically found in the upper row of the f-block. Lutetium, the last element in the lanthanide series, typically forms a +3 ion due to its electron configuration.

• Commonly used in manufacturing electronics, lasers, and strong permanent magnets.
• Their chemistry is dominated by their oxidation states, typically +3.

**Actinides:** This series includes heavier elements like lawrencium and are characterized by their radioactive nature, with some of them being only synthetically produced. Actinides are known for their ability to form multiple oxidation states and complex behavior due to the additional f-electrons.

• They are critical in nuclear energy and weapons due to their radioactive characteristics.
• Actinides tend to have shorter half-lives, making them less common in nature.

Ionic Compounds

Ionic compounds are formed when positively charged ions, known as cations, bond with negatively charged ions, known as anions. This bond results from the electrostatic forces of attraction between ions of opposite charges.

A perfect example of an ionic compound is lawrencium chloride \( \text{LrCl}_3\). In this compound, the lawrencium ion \( \text{Lr}^{3+} \) pairs with three chloride ions \( \text{Cl}^- \) to create a neutral compound.

• Ionic compounds typically form crystal lattice structures, which contribute to their high melting and boiling points.
• They often dissolve in water, conducting electricity in solution, as the ions become free to move.

Many everyday substances, such as common table salt (sodium chloride), are classic examples of ionic compounds. Their properties stem from the strong ionic bonds holding the ions together, making them stable under normal conditions.