Question

Give the physical states (gas, liquid, or solid) of the main group elements in the fourth period \((\mathrm{K}, \mathrm{Ca}, \mathrm{Ga},\) Ge, As, Se, Br) at room temperature.

Short answer

At room temperature, K, Ca, Ga, Ge, As, and Se are solids, while Br is a liquid.

Step-by-step solution

Understand the Question

To determine the physical states of the main group elements in the fourth period at room temperature, we need to know their typical states: solid, liquid, or gas.

Identify Each Element

The main group elements in the fourth period are Potassium (K), Calcium (Ca), Gallium (Ga), Germanium (Ge), Arsenic (As), Selenium (Se), and Bromine (Br).

Determine the Physical State of Solids

Potassium (K), Calcium (Ca), Gallium (Ga), Germanium (Ge), and Arsenic (As) are all metals or metalloids and thus are solid at room temperature.

Identify the State of Non-Metallic Elements

Selenium (Se) is a non-metal and is solid at room temperature. Bromine (Br) is the only non-metal that is a liquid at room temperature; it is unique in this respect among non-metallic elements.

Key concepts

Main Group Elements

The main group elements are located on the far left and far right of the periodic table. They are vital because they include the most abundant elements in the Earth's crust and atmosphere. In the context of chemistry, these elements are associated with a range of chemical behaviors and bonding patterns.
For students, understanding the main group elements is crucial because they form predictable patterns based on their position in the periodic table. This predictability relates to their valence electrons.
The main group elements in the fourth period include potassium (K), calcium (Ca), gallium (Ga), germanium (Ge), arsenic (As), selenium (Se), and bromine (Br).

• Potassium and calcium are typical metals, known for their high electrical conductivity.
• Gallium, germanium, and arsenic bridge the characteristics between metals and non-metals, often classified as metalloids.
• Selenium and bromine, being non-metals, show distinct properties, with bromine being the rare example of a liquid non-metal at room temperature.

Understanding these characteristics is key to anticipating the behavior and interactions of these elements in various chemical processes.

Fourth Period

The fourth period of the periodic table contains a significant and diverse group of elements, spanning from potassium to krypton. This period is particularly interesting because it introduces the first row containing transition metals, although the main group elements exclude them.
Main group elements of the fourth period showcase a range of properties from metals to metalloids and non-metals. This diverse composition allows us to explore various physical and chemical properties:

• We start with metals like potassium (K) and calcium (Ca), which are essential for various biological and industrial processes.
• The period continues with metalloids like gallium (Ga) and germanium (Ge), which are important in electronics due to their semiconducting properties.
• It ends with non-metals like selenium (Se) and bromine (Br), where bromine is unique as a naturally occurring liquid non-metal.

The characteristics of these elements massively influence their use in different applications, giving students insight into how these properties are practically applied.

Room Temperature

Room temperature is commonly referred to as the background temperature of a living space, which is typically around 20 to 25°C. This temperature range is crucial in chemistry because it provides a standard reference point for observing and comparing the properties of elements.
Understanding the behavior of elements at room temperature helps in predicting their state (solid, liquid, or gas) under common environmental conditions. For the main group elements in the fourth period:

• Potassium (K), calcium (Ca), gallium (Ga), germanium (Ge), arsenic (As), and selenium (Se) are all solid at room temperature. This is due to their metallic or metalloid nature which typically has strong intermolecular forces.
• Bromine (Br), on the other hand, remains in a liquid state. As a non-metal with weaker intermolecular forces, it is one of only a few elements that is liquid at this temperature.

Knowing the states of these elements at room temperature helps students better understand their chemical reactivity and interaction with other substances.