Periodic Table: Phases - Online Tutor, Practice Problems & Exam Prep

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.

Periodic Table: Phases

Hey everyone. So as we explore the periodic table and its elements, realize that at standard room temperature, which is approximately 25°C, and standard pressure, which is 1 atm, the elements can exist under three states of matter. So we have our solids, our liquids, and our gases. Now if we take a look at these three states of matter a little bit more closely, we could talk about how their molecules orient themselves.

For solids, they're kind of locked or frozen in place and they're in direct contact with one another. Because of that, they don't really conform to their container. As a result of this, we say that solids maintain a fixed shape and volume. OK, so they're kind of frozen in place the way they are. Next, we have liquids. For liquids, the molecules are in close proximity to each other, but they're able to move around more freely. So they're moving around one another. And because of this orientation, we can say that liquid, they can conform to the shape of the container, but not necessarily the volume of the container.

So think about it like this. Let's say we have a container that is 25 mL large, but we only have 10 mL of liquid. The liquid itself can conform to the shape of the container, but try as it might, because there's not enough liquid, it can't fill up the entire volume of the container. So this is what happens with liquids. Gas is on the other hand, because their molecules are so far apart from each other, this opens up new properties or expanded properties when compared to solids and liquids. We won't talk about them here, but just realize because the molecules are further apart within gaseous states of matter, we can say that because of this they assume both the shape and volume of the container.

Now if we take a look at the periodic table, we can see that a vast majority of the elements themselves are in solid form like lithium or zinc or sulfur. Some of them, very few of them are in the form of gases. So we can see that with hydrogen, nitrogen, oxygen, chlorine, and the last batch is easy to remember because they're part of group 8A which are our noble gases. So it's in the name, they're gases. And then finally we can see that the rarest form is our liquids. Under standard room temperature and pressure, there's only two elements that exist in liquid form and that would be mercury and bromine.

Now you might also see that some elements are not color-coded as solid, liquid, or gas. We find those in the 7th row from RF to OG. These elements are synthetically made within laboratories, and because they have such high masses, they're very unstable. So even at standard temperature and pressure, it's hard for us to determine what state they exist in, so they're very unpredictable. So for that reason we don't give them any state of matter at 25°C or one atmosphere. So just remember that based on these different types of temperatures and pressure, a certain state of matter is preferred by different elements.

Periodic Table: Phases Example 1

So In this example question, it says identify the element that is a representative element that is not diatomic in the second period. That assumes the shape and volume of the container that it is in. So there's a lot of information being thrown at us right now. First, we're going to say it is a representative element. Remember, representative elements is just one of the large categories for the elements of the periodic table.

If your representative element, that means you cannot be a transition metal. Unfortunately, all of these choices are representative elements. None of them are transition metals, so that part is not going to help us. Well, next, it is not diatomic. Well, here beryllium is monoatomic, silicon is monoatomic, boron is monoatomic. Neon and argon. So that also is not going to help us too much.

Now they're getting to some important stuff. They're saying second period. So second period means that in the 2nd row of the periodic table, and they say that it assumes the shape and volume of the container that it is in. So if it assumes both shape and volume, that means that it is a gas. So basically this question is asking us to find an element that's in the 2nd row of the periodic table and is also a gas.

So come up here, We're going to say 2nd row is here and the only ones that are gases are Nitrogen, oxygen, fluorine and neon. But out of those four, neon is the only one that's given to us as a choice. So that would mean that option D would be our correct answer.

So everything we've been learning about the periodic table, it adds on top of one another. You've got to remember representative elements versus transition metals. You have to remember phases. You have to remember elemental forms. This is the key to getting the type of question like this correct. So again, the only thing that fits all of these descriptions perfectly would be option D NEON.

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

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

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

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

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).