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Sarah Bradstreet

GED Science: The Periodic Table

Chemistry is an important topic on the GED Science subject test. You’ll want to know the basics about atoms and elements and the place to go for that information is the periodic table. Read on to learn what the periodic table is and how to use one.

What is the Periodic Table?

The periodic table of the elements is a chart that lists all of the known elements and organizes them according to their characteristics.

GED Science The Periodic Table

Do I Have to Memorize the Periodic Table for the GED Science Test?

No! You do not need to have any information from the periodic table memorized for the GED Science test. What you should know is how to read one. If the test wants you to give information that’s on the table, they will show you one and ask you to pull information from it.

How Do I Read the Periodic Table?

The periodic table tells you a lot of information about each element. Some periodic tables are complex and give tons of information. If you see a periodic table on the GED Science test, it will be a simple one with a few basic pieces of information on it.

Let’s take a look at one element from the table up close.

GED Science: The Periodic Table

This is carbon. By looking at its box on the periodic table, we can learn some key information about it.

GED Science: The Periodic Table

Let’s start off with any easy one. The first thing you’ll find is the element’s name.

GED Science: The Periodic Table

You’ll also find its chemical symbol. A chemical symbol is one or two letters that are used to represent the element. When scientists write chemical equations, they use these symbols instead of the elements’ names. It makes it a lot faster and easier.

Plus, these symbols are used internationally, while the actual element names might change from language to language. For example, in German, carbon is known as kohlenstoff, but the chemical symbol is still C, so scientists from different countries can still understand each other. In English, most of the time, the chemical symbol matches the first one or two letters of the elements name. There are a few odd balls, though, that usually have to do with the Latin origins of the element names. Some examples are Pb for lead, Au for gold, and K for potassium.

The next bit of information you’ll find is the atomic number. Every element has a unique atomic number, and the elements are listed in order of atomic number on the periodic table. The atomic number is the number of protons contained in one atom of the element. Carbon, for instance, has an atomic number of 6, so we know that a carbon atom has 6 protons. The atomic number also tells you the number of electrons the atom has, since the number of protons and electrons are the same to create a balanced (neutral) overall atomic charge.

Finally, the periodic table tells you the atomic mass of each element. This is the mass of one atom of a given element. The unit used to measure atomic mass is known as atomic mass units (AMU). As you can see, the mass of carbon is 12.011 AMU.

With a little rounding, you can use the atomic mass to figure out the number of neutrons in an atom of the element. An element’s atomic mass is approximately equal to the sum of its protons and neutrons, since electrons are so tiny that their mass is almost negligible. So (# of protons) + (# of neutrons) = atomic mass. Let’s take a look at carbon again. The atomic mass is about 12, and we already know from the atomic number that there are 6 protons, so that means there are 6 neutrons in a carbon atom, since 6 + 6 = 12.

In carbon’s case, the number of protons and neutrons happen to be the same, but this isn’t always true. Look at beryllium (Be). Its atomic mass is about 9, and its atomic number (and number of protons) is 4. That means it has 5 neutrons, since 4 + 5 = 9.

Periodic Table Practice

Here are some questions to help you practice for the GED Science subject test. Use the periodic table to find the information (answers below). Here’s the periodic table again, but larger, so that you can read each cell clearly.

  1. What is the name of the element with an atomic number of 12?
  2. What is the chemical symbol for iron?
  3. What is the atomic mass of an atom of krypton?
  4. What is the atomic number of silver?
  5. How many protons are in an atom of helium?
  6. How many electrons are in an atom of sodium?
  7. How many neutrons are in an atom of neon?
  8. How many neutrons are in an atom of potassium?


Answer Key

  1. Magnesium
    Just look for the big, bold number 12 and read the full name of the element.
  2. Fe
    Fe is the symbol for iron, with an atomic number of 26.
  3. 83.80
    Read below the big K for krypton to find its atomic mass.
  4. 47
    Look for the big, bold number on the box for silver (Ag).
  5. 2
    Helium (He) has an atomic number of 2, which means there are 2 protons in its nucleus.
  6. 11
    Sodium (Na) has an atomic number of 11, which means there are 11 electrons in one atom of the element. Remember, the number of electrons and protons are the same.
  7. 10
    The mass of neon (Ne) is about 20. Subtract the number of protons (10) to find the number of neutrons (10).
  8. 20
    The mass of potassium (K) is about 39. Subtract the number of protons (19) to find the number of neutrons (20).
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About Sarah Bradstreet

Sarah is an educator and writer with a Master’s degree in education from Syracuse University who has helped students succeed on standardized tests since 2008. She loves reading, theater, and chasing around her two kids.

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