Do I Need to Memorize the MCAT^® Periodic Table?

The AAMC's Chem/Phys content outline says "a periodic table will be provided during the exam," and the Bio/Biochem outline says the same. Both outlines print the table itself, so you can see the version you'll use months before you sit for the test.

Each box gives you three pieces of data, according to UWorld's guide to the MCAT periodic table: the atomic symbol, the atomic number and the atomic mass. The layout tells you each element's row and column, too. Everything else is up to you.

The missing names catch people. If a passage mentions manganese or selenium, you need to know that they're Mn and Se before you can look anything up. UWorld also points out that the table lists atomic mass, an average across isotopes, and not the mass number of any one isotope. A question about carbon-14 expects you to know where the 14 comes from.

Content category 4E of the Chem/Phys outline lists the periodic table topics in two groups. The first is classifying elements into groups by electronic structure:

• Groups by name: alkali metals, alkaline earth metals, halogens, noble gases and transition metals.
• Broader categories: representative elements, metals and nonmetals, and the oxygen group.

The second is how chemical properties change with group and row:

• Valence electrons.
• First and second ionization energy: the definition, and predicting it from electronic structure for elements in different groups or rows.
• Electron affinity: the definition, and how it changes with group and row.
• Electronegativity: the definition, and "comparative values for some representative elements and important groups."
• Size: how electron shells set the sizes of atoms and of ions.

The wording on electronegativity tells you how deep to go. Expect to rank fluorine, oxygen and chlorine, or to say which bond in a molecule is more polar, without needing any value to two decimal places.

Blueprint's summary of periodic trends gives the directions like this:

You don't have to memorize four separate rules, because one idea drives all of them. Moving across a row, each element adds a proton to the nucleus while its new electron goes into the same shell. The effective nuclear charge goes up, so the nucleus pulls the outer electrons closer and holds them more tightly. The atom shrinks, and its electrons get harder to remove and easier to attract.

Moving down a group, each element adds a new shell. The outer electrons are farther from the nucleus, with more inner electrons shielding them, so the atom gets bigger and lets go of electrons more easily. Blueprint puts it in one line: "the greater the effective nuclear charge, the smaller the atomic radius."

Ions follow the same logic. A cation is always smaller than its parent atom, and an anion is larger. Blueprint also notes that the noble gases have no electronegativity values.

Ionization energy rises across a row, but not smoothly. Here's period 2, using values from the ionization energy table in Principles of General Chemistry.

Neon's first ionization energy is four times lithium's, 2,081 kJ/mol against 520. Two elements break the climb, and both are testable, because the outline asks you to predict ionization energy "from electronic structure."

• Boron, 801 against beryllium's 900: Premier's MCAT notes on the exceptions explain that boron's outermost electron "sits in the higher-energy 2p subshell, where it is easier to remove," while beryllium's full 2s subshell makes it slightly harder to ionize.
• Oxygen, 1,314 against nitrogen's 1,402: Oxygen "is the first period-2 element forced to put two electrons in one 2p orbital," and "the repulsion between them makes it easier to remove one." Nitrogen's half-filled 2p subshell has no paired electrons.

Second ionization energy has a pattern of its own. Successive ionization energies jump sharply once you start pulling electrons out of a noble-gas core. Wikipedia's ionization energy entry uses magnesium as the example: its first two ionization energies, which remove the two 3s electrons, are "much smaller than the third, which requires stripping off a 2p electron from the neon configuration of Mg2+." A passage that shows you a list of successive ionization energies for an unknown element is asking you to find that jump. The jump comes after the second electron, so the element is in group 2.

Symbols for the elements you'll meet in passages. UWorld's list of high-yield elements includes C, N, O, Na, Mg, P, Cl, K, Ca, Fe and I. Add H and S, and drill the four whose symbols don't match their English names: Na for sodium, K for potassium, Fe for iron and, if a passage strays into metals, Cu for copper.

The electronegativity order of the common nonmetals. The values come from Wikipedia's electronegativity data page, which uses the Pauling scale.

Memorize the ranking, F, O, Cl, N, C, H, and two facts it gives you. First, nitrogen is less electronegative than chlorine, which trips people who expect row 2 to beat row 3 every time. Second, carbon and hydrogen are only 0.35 apart, which is why C-H bonds count as nonpolar in organic chemistry. At the other end, sodium is 0.93 and potassium 0.82, so their bonds to chlorine are ionic.

How each group behaves. Alkali metals give up one electron to form +1 ions, and alkaline earth metals give up two to form +2 ions. Halogens pick up one electron to form -1 ions. Noble gases already have a full valence shell, so they barely react. Transition metals can take more than one oxidation state, and the table won't tell you which, so read the passage for the charge.

The reason behind the trends. If you can explain effective nuclear charge and shielding, you can rebuild every row of the trend table on the spot. Write the explanation on one flashcard and the four directions on four more, in the atomic flashcard style where each card tests one fact. Then let spaced repetition bring them back on schedule.

Use a periodic table with the same layout as the AAMC's while you do practice questions, so you're used to finding elements by symbol alone. The PurpleCAT interactive periodic table works for that drill, and it's handy for checking trends while you review.

Do molar mass problems by rounding the atomic masses you're given. Oxygen's 16.00 and carbon's 12.01 are close enough to 16 and 12 that you can do the arithmetic on the noteboard, which matters because there's no calculator on the MCAT.

The periodic table is one more place where the MCAT^® gives you the reference data and tests what you do with it. Formulas follow a similar rule, and the list of formulas to memorize sorts them the same way. To see how category 4E fits with the rest of the exam, read the breakdown of the four MCAT sections.

• Do you get a periodic table on the MCAT? Yes. The AAMC's Chem/Phys and Bio/Biochem outlines both say a periodic table is provided during the exam.
• Does it show element names? No. It shows each element's symbol, atomic number and atomic mass.
• Does it show electronegativity or ionization energy? No. You need to know those trends, and the electronegativity order of the common nonmetals, from memory.
• Do you need to memorize atomic masses? No. They're on the table. Round them for quick math.

Last verified October 30, 2026, against the AAMC's content outlines for Chem/Phys and Bio/Biochem.