Periodic Table: Phases (Simplified): Videos & Practice Problems

At standard room temperature (25°C) and pressure (1 atm), elements can exist as solids, liquids, or gases. Solids maintain a fixed shape and volume due to tightly packed molecules. Liquids conform to the shape of their container but not the volume, while gases assume both shape and volume due to widely spaced molecules. Most elements are solids, with only mercury and bromine as liquids, and a few gases like hydrogen and oxygen. Synthetic elements in the 7th row are unstable, making their states unpredictable under these conditions.

Periodic Table: Phases (Simplified) Concept 1

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 you have 10 mL of water in a 25 mL container, the water will fill the bottom of the container but will not occupy 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 crucial in understanding gas behavior in various applications.

When examining the periodic table, most elements are found in solid form, such as lithium, zinc, and sulfur. A few elements, like hydrogen, nitrogen, oxygen, and chlorine, exist as gases, with the noble gases in group 8A being notable examples. 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.

Understanding these states of matter and their properties is fundamental in chemistry, as it helps explain how different elements behave under various conditions.

Periodic Table: Phases (Simplified) Example 1

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, indicating it is a gas. Representative elements are those that are not transition metals, which helps narrow down our options. In the second period, the elements include beryllium, boron, carbon, nitrogen, oxygen, fluorine, neon, and sodium. Among these, beryllium, boron, carbon, and silicon are monoatomic, while neon and argon are noble gases.

The key detail here is that the element must be a gas, which means it must take both the shape and volume of its container. In the second period, the gases present are nitrogen, oxygen, fluorine, and neon. Out of these, only neon is a noble gas and fits the criteria of being a representative element. Therefore, the correct answer to the question is option d, neon.

This exercise emphasizes the importance of understanding the periodic table's structure, including the distinction between representative elements and transition metals, as well as recognizing the physical states of elements. By synthesizing these concepts, we can effectively solve similar questions in the future.

Which of the following elements is a nonmetal that is a 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 states of matter for elements at standard room temperature and pressure?

At standard room temperature (25°C) and pressure (1 atm), elements can exist in three states of matter: solids, liquids, and gases. Solids have tightly packed molecules, maintaining a fixed shape and volume. Liquids have molecules that are close but can move around, allowing them to conform to the shape of their container but not the volume. Gases have widely spaced molecules, enabling them to assume both the shape and volume of their container. Most elements are solids, a few like hydrogen and oxygen are gases, and only mercury and bromine are liquids under these conditions.

Which elements are liquids at room temperature?

At standard room temperature (25°C) and pressure (1 atm), only two elements exist in liquid form: mercury (Hg) and bromine (Br). These elements are unique because their molecular structures allow them to remain in a liquid state under these conditions, unlike most other elements which are either solids or gases.

Why do gases assume both the shape and volume of their container?

Gases assume both the shape and volume of their container because their molecules are widely spaced and move freely. This allows gas molecules to spread out and fill any available space, conforming to the shape and volume of the container. This behavior contrasts with solids, which have tightly packed molecules, and liquids, which have closely packed but more mobile molecules.

Why are synthetic elements in the 7th row of the periodic table unpredictable in their state of matter?

Synthetic elements in the 7th row of the periodic table, from Rutherfordium (Rf) to Oganesson (Og), are unpredictable in their state of matter because they are highly unstable and have very high atomic masses. These elements are created in laboratories and often have very short half-lives, making it difficult to determine their state at standard room temperature (25°C) and pressure (1 atm). Their instability and rapid decay contribute to the uncertainty in their physical states.

How do the molecular orientations of solids, liquids, and gases differ?

In solids, molecules are tightly packed and locked in place, giving solids a fixed shape and volume. In liquids, molecules are close together but can move around each other, allowing liquids to conform to the shape of their container but not the volume. In gases, molecules are widely spaced and move freely, enabling gases to assume both the shape and volume of their container. These differences in molecular orientation account for the distinct properties of each state of matter.