Periodic Table: Phases: Videos & Practice Problems

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 different phases of elements in the periodic table at room temperature?

At standard room temperature (approximately 25°C) and pressure (1 atmosphere), elements in the periodic table exist in three primary phases: solids, liquids, and gases. Most elements are solids, where their molecules are tightly packed and fixed in place, giving them a definite shape and volume. A few elements, such as mercury (Hg) and bromine (Br), exist as liquids; their molecules are close but can move around, allowing them to conform to the shape of their container but not its volume. Gaseous elements, like hydrogen (H₂), nitrogen (N₂), oxygen (O₂), chlorine (Cl₂), and noble gases (group 8A), have molecules far apart, so they take both the shape and volume of their container. Some synthetic elements with high atomic numbers have unpredictable phases due to instability.

Why do solids maintain a fixed shape and volume compared to liquids and gases?

Solids maintain a fixed shape and volume because their molecules are closely packed and locked in place. This molecular arrangement restricts movement, so solids do not conform to the shape of their container. In contrast, liquids have molecules that are close but can move around each other, allowing them to take the shape of their container while maintaining a fixed volume. Gases have molecules that are widely spaced and move freely, enabling them to expand and fill both the shape and volume of their container. The rigidity of solids arises from strong intermolecular forces that hold molecules in fixed positions.

Which elements exist as liquids at room temperature and why are they rare?

At room temperature and standard pressure, only two elements exist as liquids: mercury (Hg) and bromine (Br). These elements are rare in the liquid phase because most elements have melting points either well above or below room temperature. Mercury is a metal with a relatively low melting point, allowing it to remain liquid at 25°C. Bromine is a halogen with a melting point just below room temperature, so it also exists as a liquid under these conditions. The rarity of liquid elements is due to the specific balance of intermolecular forces and atomic structure that allow these two elements to be liquid at standard conditions.

Why are the phases of synthetic elements in the 7th period difficult to determine?

Synthetic elements in the 7th period, such as those from Rutherfordium (Rf) to Oganesson (Og), are difficult to classify in terms of phase at room temperature because they are highly unstable and have very short half-lives. Their high atomic masses and rapid radioactive decay make it challenging to observe their physical properties directly. As a result, their states of matter under standard conditions are unpredictable and often not assigned. These elements are typically produced in laboratories in very small quantities, further complicating phase determination.

How do gases differ from solids and liquids in terms of molecular arrangement and container conformity?

Gases differ significantly from solids and liquids in molecular arrangement and behavior. Gas molecules are spaced far apart and move freely, which allows gases to expand and fill both the shape and volume of their container. In contrast, solids have molecules tightly packed and fixed, maintaining a definite shape and volume, while liquids have molecules close together but able to move around, conforming to the container's shape but not its volume. This molecular freedom in gases results in properties like compressibility and expansion, which are not observed in solids or liquids under standard conditions.