Periodic Table: Phases: Videos & Practice Problems

Understanding the states of matter—solids, liquids, and gases—is essential when exploring the periodic table's elements. At standard room temperature (25 degrees Celsius) and pressure (1 atmosphere), elements exhibit distinct physical properties based on their molecular arrangements. Solids maintain a fixed shape and volume due to closely packed, immobile molecules. Liquids, with molecules that move more freely, conform to the shape but not the volume of their containers. Gases, with widely spaced molecules, assume both the shape and volume of their containers. Most elements are solid under these conditions, with exceptions like hydrogen and oxygen, which are gases, and mercury and bromine, which are liquids. Elements synthesized in laboratories, such as those with high atomic numbers, often have unpredictable states due to their instability, making their classification at standard conditions challenging.

Element States of Matter

As we delve into the periodic table, it's essential to understand how elements exist in different states of matter at standard room temperature (approximately 25 degrees Celsius) and standard pressure (1 atmosphere). The three primary states are solids, liquids, and gases, each characterized by the arrangement and movement of their molecules.

In solids, molecules are tightly packed and locked in place, resulting in a fixed shape and volume. This rigidity means that solids do not conform to the shape of their container. For example, a block of ice retains its shape regardless of the container it is placed in.

Liquids, on the other hand, have molecules that are close together but can move around more freely. This allows liquids to take the shape of their container while maintaining a constant volume. For instance, if a liquid occupies only 10 mL in a 25 mL container, it will fill the shape of the container but will not fill the entire volume.

Gases exhibit a different behavior; their molecules are spaced far apart, which allows them to expand and fill both the shape and volume of their container. This property is a significant distinction from solids and liquids.

When examining the periodic table, most elements are found in solid form, such as lithium, zinc, and sulfur. A few elements exist as gases, including hydrogen, nitrogen, oxygen, and chlorine, along with the noble gases in group 8A. The rarest state is liquid, with only two elements—mercury and bromine—existing as liquids under standard conditions.

Additionally, some elements, particularly those in the seventh row (from francium to oganesson), are synthetically produced in laboratories. Due to their high atomic masses and instability, their state of matter at standard temperature and pressure is unpredictable, which is why they are not assigned a specific state.

In summary, the state of matter for different elements is influenced by temperature and pressure, with solids, liquids, and gases exhibiting distinct molecular arrangements and behaviors.

Second Period State of Matter Example

In this scenario, we are tasked with identifying a representative element from the second period of the periodic table that is not diatomic and assumes the shape and volume of its container. Understanding the classification of elements is crucial; representative elements are those that are not transition metals, which helps narrow down our options. In the second period, we find elements such as beryllium, boron, carbon, nitrogen, oxygen, fluorine, neon, and argon. Among these, beryllium, boron, carbon, and silicon are monoatomic, while nitrogen, oxygen, fluorine, and neon are gases.

The key phrase in the question is that the element "assumes the shape and volume of the container," indicating that it must be a gas. In the second period, the gaseous elements are nitrogen (N), oxygen (O), fluorine (F), and neon (Ne). However, since we are looking for a representative element that is not diatomic, we can eliminate nitrogen (N) and oxygen (O) as they exist as diatomic molecules (N₂ and O₂ respectively). This leaves us with fluorine (F) and neon (Ne).

Fluorine is also diatomic (F₂), which means the only option that fits all criteria is neon (Ne). Neon is a noble gas, known for being monoatomic and existing in a gaseous state at room temperature. Therefore, the correct answer to the question is neon (option d), as it perfectly meets all the specified conditions.

Which of the following elements is a nonmetal that is a homonuclear polyatomic solid?

• A. Carbon
• B. Oxygen
• C. Sulfur
• D. Radon
• E. Cesium

Answer: (C)

Which of the following exists as a diatomic solid at room temperature?

• A. Bromine
• B. Tellurium
• C. Sulfur
• D. Chlorine
• E. Iodine

Answer: (E)

Here’s what students ask on this topic:

What are the three states of matter and how do their molecular arrangements differ?

The three states of matter are solids, liquids, and gases. In solids, molecules are closely packed and immobile, maintaining a fixed shape and volume. In liquids, molecules are in close proximity but can move around more freely, allowing the liquid to conform to the shape but not the volume of its container. In gases, molecules are widely spaced and move independently, enabling the gas to assume both the shape and volume of its container.

Which elements are liquids at standard room temperature and pressure?

At standard room temperature (25 degrees Celsius) and pressure (1 atmosphere), the elements that exist in liquid form are mercury (Hg) and bromine (Br). These are the only two elements that are liquids under these conditions.

Why are some elements on the periodic table not classified as solids, liquids, or gases?

Some elements, particularly those in the 7th row from Rutherfordium (Rf) to Oganesson (Og), are synthetically made in laboratories and have very high atomic masses. These elements are highly unstable, making it difficult to determine their state of matter at standard room temperature and pressure. Due to their instability and unpredictability, they are not classified as solids, liquids, or gases under these conditions.

How do gases differ from solids and liquids in terms of their properties?

Gases differ from solids and liquids in that their molecules are widely spaced and move independently. This allows gases to assume both the shape and volume of their containers. In contrast, solids have closely packed, immobile molecules that maintain a fixed shape and volume, while liquids have molecules that move more freely, conforming to the shape but not the volume of their containers.

Which elements are gases at standard room temperature and pressure?

At standard room temperature (25 degrees Celsius) and pressure (1 atmosphere), the elements that exist in gaseous form include hydrogen (H), nitrogen (N), oxygen (O), fluorine (F), chlorine (Cl), and the noble gases in group 8A: helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn).