What’s on the MCAT® Periodic Table?
The Association of American Medical Colleges (AAMC®) provides a periodic table on the Medical College Admission Test (MCAT®). The on-screen resource can be accessed through an “exhibit” button in the testing interface that opens in a resizable pop-up window. You won’t have to need to memorize the entire periodic table, but you should be familiar enough with it to find the information you need quickly under timed conditions.
According to AAMC’s section overviews, the periodic table is available in the two sections that test chemistry:
- Chemical and Physical Foundations of Biological Systems (Chem/Phys)
- Biological and Biochemical Foundations of Living Systems (Bio/Biochem)
What Does the MCAT Periodic Table Include?
Every element box on the periodic table gives you three data points:
- Atomic symbol
- Atomic number
- Atomic mass
| On the MCAT Periodic Table | Not on the MCAT Periodic Table |
|---|---|
|
|
A couple of things to keep in mind:
- The table doesn’t show element names, only symbols.
- The table only shows the atomic mass, not the molar mass or mass number of a specific isotope referenced in a passage.
Beyond the symbol, number, and atomic mass, you’ll need to know the periodic trends, group and period patterns, and high-yield elements covered on this page.
MCAT Periodic Table Groups and Periods to Know
Every trend you’ll use on the MCAT comes down to one thing: where an element sits on the table. Elements are organized in two ways, and each tells you something different about how it behaves.
- Groups (columns): The elements share the same number of valence electrons, which is why elements in the same group react in similar ways.
- Periods (rows): The elements share the same number of electron shells, which is why properties shift predictably as you move left to right.
Group membership predicts reactivity directly, since elements in the same column have the same valence electron count. These five groups show up most often across Chem/Phys and Bio/Biochem passages.
| Group | Name | Key Properties for the MCAT | Notable Elements |
|---|---|---|---|
| Group 1 | Alkali Metals | One valence electron; highly reactive with water; form +1 ions | Li, Na, K (critical for membrane biology) |
| Group 2 | Alkaline Earth Metals | Two valence electrons; form +2 ions; less reactive than Group 1 | Mg, Ca (bone, muscle signaling, enzyme cofactors) |
| Group 3–12 | Transition Metals | Variable oxidation states; form colored compounds; catalytic roles | Fe, Cu, Zn (hemoglobin, enzymes, redox reactions) |
| Groups 13–16 (specifically the metals located beneath the metalloid staircase) | Post-transition metals | Softer metals with lower melting and boiling points than transition metals; possess typical metallic properties such as high thermal and electrical conductivity, malleability, and ductility; typically form cations | Al, Sn, Pb, Bi (often encountered in electrochemistry, galvanic cells, and radioactive decay passages) |
| Staircase (B, Si, Ge, As, Sb, Te) | Metalloids | Intermediate properties between metals and nonmetals; semimetallic conductivity | B, Si, As (semiconductors, trace elements) |
| Upper Right (Non-halogen) | Non-metals | High ionization energy and electronegativity; form covalent bonds; poor conductors | C, N, O, P, S (foundational to all biological macromolecules) |
| Group 17 | Halogens | Seven valence electrons; highly electronegative; form -1 ions | F, Cl, Br, I (thyroid hormones, disinfection) |
| Group 18 | Noble Gases | Full valence shells; chemically inert; no electronegativity | He, Ne, Ar (no biological role) |
| f-block (Period 6) | Lanthanides | Inner transition metals; +3 dominant oxidation state; rare in MCAT biology contexts | Ce, Nd, Eu (rarely tested, industrial/laser applications) |
| f-block (Period 7) | Actinides | Radioactive elements; filling 5f subshell; actinoid series | U, Th, Pu (nuclear/decay chemistry contexts) |
| Period | Name | Key Properties for the MCAT | Notable Elements |
|---|---|---|---|
| Period 1 | First Row Elements | Only period made up entirely of s-block elements, with just one electron shell each | H, He (foundational for acid-base and redox contexts) |
| Period 2 | Second Row Elements | Includes s- and p-block elements; forms the backbone of organic and biological molecules | C, N, O, F (essential in all biomolecules) |
| Period 3 | Third Row Elements | Adds a full electron shell over Period 2; larger atomic radii, lower electronegativity than Period 2 counterparts | Na, P, S, Cl (electrolytes, biochemistry passages) |
| Period 4 | Fourth Row Elements | First row to include d-block transition metals | Fe, Cu, Zn (biochemical cofactors) |
MCAT Periodic Table Trends You Must Know
Learn these periodic trends before test day so you can recognize patterns quickly and apply them to your general chemistry and organic chemistry questions.
Electron configuration is the arrangement of an atom’s electrons across shells and subshells, built by filling lower-energy orbitals before higher ones, according to the Aufbau principle.
- What it determines: Group position reflects an atom’s valence electron arrangement; period position reflects its number of occupied shells.
- MCAT application: The table gives you the atomic number, which tells you electron count, but not arrangement. You’re expected to derive configuration yourself.
Atomic radius is the size of an atom, typically measured as half the distance between two bonded nuclei of the same element.
- Across a period: Decreases left to right, as added protons pull the same valence shell inward while inner shielding stays constant.
- Down a group: Increases, as each new shell sits farther out, shielded by the shells beneath it.
- MCAT application: Determines bond length and how atoms pack into larger structures; smaller radius is also why ionization energy, electronegativity, and electron affinity all rise together.
- Exception: Cations are smaller than their neutral parent atom, and anions are larger, relevant in ion transport and membrane passages.
Ionization energy is the energy required to remove the outermost electron from a neutral, gaseous atom.
- Across a period: Increases left to right, as greater nuclear charge pulls outer electrons in tighter.
- Down a group: Decreases, as outer electrons sit farther out and are more heavily shielded.
- MCAT application: A sharp jump between successive ionization energies signals the next electron is being pulled from an inner shell, tested often in Chem/Phys passages.
- Exception: Noble gases have the highest IE in their period, since a full valence shell resists losing an electron.
Electronegativity is a measure of how strongly an atom attracts shared electrons in a covalent bond, with fluorine sitting highest on the table at 4.0 on the Pauling scale.
- Across a period: Increases left to right, as smaller radius and higher nuclear charge pull bonding electrons harder.
- Down a group: Decreases, as larger radius and greater shielding weaken that pull.
- MCAT application: Electronegativity differences between bonded atoms drive bond polarity, molecular polarity, solubility, and intermolecular forces, all high-frequency across Chem/Phys and Bio/Biochem.
- Exception: Noble gases have no assigned electronegativity value, since their full valence shells resist bonding entirely.
Electron affinity is the energy released when a neutral, gaseous atom gains an electron to form an anion.
- Across a period: Generally more exothermic left to right, as higher nuclear charge releases more energy on adding an electron.
- Down a group: Less exothermic, as larger atoms hold an added electron less tightly.
- MCAT application: Explains why halogens form -1 anions so readily, they have the highest electron affinity of any group.
- Exception: Group 2 and Group 18 have near-zero or slightly endothermic values, since their orbitals are already filled or stable.
Metallic character describes how readily an element loses electrons and displays metal-like properties such as conductivity and malleability, and it’s the one category the MCAT table gives zero labeling for: no color-coding, no classification, position alone tells you.
- Metals (left and middle of the table): lose electrons easily, low ionization energy, low electronegativity, strong conductors.
- Nonmetals (upper right): gain electrons readily, high ionization energy, high electronegativity, poor conductors.
- Metalloids (the staircase: boron, silicon, germanium, arsenic, antimony, tellurium): intermediate properties, behaving like a metal or nonmetal depending on what they react with.
- Across a period/down a group: Metallic character decreases left to right, increases down a group.
- MCAT application: Metalloid behavior shows up in semiconductor and trace-element passages; metallic character is often the fastest way to predict which species gets oxidized versus reduced in a reaction.
Oxidation state is the charge an atom would have if all its bonds were fully ionic, and it follows directly from how readily an element gains or loses electrons.
- Metals: Tend toward positive, often variable oxidation states. Transition metals like iron and copper commonly cycle between states, for example Fe²⁺ and Fe³⁺, which is exactly why they function as biochemical cofactors.
- Nonmetals: Tend toward negative oxidation states, gaining electrons to fill their valence shell, halogens at -1 being the clearest case.
- MCAT application: Oxidation state tracking is the core mechanic for identifying what’s oxidized and what’s reduced in a redox reaction, tested constantly in electron transport and metabolism passages.
Effective nuclear charge is the net positive charge a valence electron actually experiences, after accounting for shielding from inner-shell electrons, and it’s the single concept underneath every trend above.
- Across a period: Increases, as protons increase while inner shielding stays constant.
- Down a group: Stays roughly constant for valence electrons, since each new period adds both protons and a full shielding shell, even though those valence electrons sit farther out.
- MCAT application: Higher Zeff means smaller radius, higher ionization energy, and higher electronegativity.
Quick Reference: MCAT Periodic Trends Summary
Use this table for a quick review before test day. While these are basic chemistry rules, the MCAT won't just ask you to recite them. Passages will test whether you truly understand why these trends happen, not just which direction they go.
| Trend | Across a Period | Down a Group | Exception to Know |
|---|---|---|---|
| Atomic radius | Decreases | Increases | Cation < neutral atom < anion |
| Ionization energy | Increases | Decreases | Sharp jump signals removal from an inner shell |
| Electronegativity | Increases | Decreases | Noble gases = no assigned EN value; F is highest overall |
| Electron affinity | More exothermic | Less exothermic | Group 2 and Group 18 ≈ 0 or slightly endothermic |
| Metallic character | Decreases | Increases | Metalloids sit between metal and nonmetal behavior |
| Effective nuclear charge (Zeff) | Increases | Constant for valence electrons | Underlies every trend above |
| Trend | Across a Period | Down a Group | Exception to Know |
|---|---|---|---|
| Atomic radius | Decreases | Increases | Cation < neutral atom < anion |
| Ionization energy | Increases | Decreases | Sharp jump signals removal from an inner shell |
| Electronegativity | Increases | Decreases | Noble gases = no assigned EN value; F is highest overall |
| Electron affinity | More exothermic | Less exothermic | Group 2 and Group 18 ≈ 0 or slightly endothermic |
| Metallic character | Decreases | Increases | Metalloids sit between metal and nonmetal behavior |
| Effective nuclear charge (Zeff) | Increases | Constant for valence electrons | Underlies every trend above |
Electron configuration and oxidation states aren’t included above since neither reduces to a single directional trend the way the six above do. Electron configuration is the foundation those trends are built on, and oxidation states depend on whether an element tends to lose electrons (metals, positive states) or gain them (nonmetals, negative states), both covered in the section above.
High-Yield Elements to Know for the MCAT
While AAMC provides the periodic table during both the Chem/Phys and Bio/Biochem MCAT sections. There are few elements that appear consistently across both sections because of the biological role they play, involving ion channels and neurotransmission. Here’s an overview of these elements’ biological role and their core chemical property.
| Element | Symbol | Biological Role | Property to Know |
|---|---|---|---|
| Carbon | C (Z=6) | Backbone of all organic and biomolecules | Four valence electrons; tetravalent; forms double and triple bonds |
| Nitrogen | N (Z=7) | Amino groups, nucleic acid bases, neurotransmitters | Three bonds + lone pair; basic in amines; acidic in amides |
| Oxygen | O (Z=8) | Redox reactions, water, carbonyl groups, ATP | Highly electronegative; two lone pairs; forms hydrogen bonds |
| Sodium | Na (Z=11) | Action potentials, osmolarity, cell membrane function | Group 1; +1 ion; high reactivity with water |
| Magnesium | Mg (Z=12) | Enzyme cofactor, chlorophyll, DNA stabilization | Group 2; +2 ion; enzyme activator |
| Phosphorus | P (Z=15) | ATP, nucleic acids, phospholipids, bone | Forms PO₄³⁻; pentavalent in some contexts |
| Chlorine | Cl (Z=17) | Stomach acid (HCl), osmolarity, nerve signaling | Group 17 halogen; highly electronegative; -1 ion |
| Potassium | K (Z=19) | Resting membrane potential, heart rhythm, osmoregulation | Group 1; +1 ion; largest common biological cation |
| Calcium | Ca (Z=20) | Muscle contraction, second messenger, bone mineral | Group 2; +2 ion; triggers neurotransmitter release |
| Iron | Fe (Z=26) | Hemoglobin, myoglobin, electron transport chain | Transition metal; Fe²⁺/Fe³⁺ redox; catalytic in cytochromes |
| Iodine | I (Z=53) | Thyroid hormones (T3, T4) | Group 17 halogen; largest common biological anion |
| Element | Symbol | Biological Role | Property to Know |
|---|---|---|---|
| Carbon | C (Z=6) | Backbone of all organic and biomolecules | Four valence electrons; tetravalent; forms double and triple bonds |
| Nitrogen | N (Z=7) | Amino groups, nucleic acid bases, neurotransmitters | Three bonds + lone pair; basic in amines; acidic in amides |
| Oxygen | O (Z=8) | Redox reactions, water, carbonyl groups, ATP | Highly electronegative; two lone pairs; forms hydrogen bonds |
| Sodium | Na (Z=11) | Action potentials, osmolarity, cell membrane function | Group 1; +1 ion; high reactivity with water |
| Magnesium | Mg (Z=12) | Enzyme cofactor, chlorophyll, DNA stabilization | Group 2; +2 ion; enzyme activator |
| Phosphorus | P (Z=15) | ATP, nucleic acids, phospholipids, bone | Forms PO₄³⁻; pentavalent in some contexts |
| Chlorine | Cl (Z=17) | Stomach acid (HCl), osmolarity, nerve signaling | Group 17 halogen; highly electronegative; -1 ion |
| Potassium | K (Z=19) | Resting membrane potential, heart rhythm, osmoregulation | Group 1; +1 ion; largest common biological cation |
| Calcium | Ca (Z=20) | Muscle contraction, second messenger, bone mineral | Group 2; +2 ion; triggers neurotransmitter release |
| Iron | Fe (Z=26) | Hemoglobin, myoglobin, electron transport chain | Transition metal; Fe²⁺/Fe³⁺ redox; catalytic in cytochromes |
| Iodine | I (Z=53) | Thyroid hormones (T3, T4) | Group 17 halogen; largest common biological anion |
Common Mistakes Students Make With the MCAT Periodic Table
The periodic table gives you the atomic symbol, number, and mass. It doesn’t correct you when you misread one, confuse a value, or flip a direction under pressure. These are the three things students miss most.
- Not recognizing element symbols: The table shows symbols, not full names. Hesitating over whether K is potassium or Kr is krypton wastes time, especially in a passage that moves between several elements quickly.
- Confusing atomic mass with mass number: The table shows standard atomic mass, a weighted average across isotopes, not the mass number of a specific isotope a passage might reference. Using the wrong one leads directly to calculation errors in stoichiometry and nuclear chemistry questions.
- Getting oxidation state direction backward under pressure: Metals trend positive, and nonmetals trend negative. It appears straightforward on paper but can easily be flipped mid-passage, especially with transition metals that carry multiple stable states.
These mistakes happen when you expect the table to do the thinking for you. Memorize key element symbols, distinguish atomic mass from mass number, and practice oxidation rules in advance so you stay fast and accurate on test day.
UWorld's practice exams are the fastest way to confirm you’re ready for test day and know how to incorporate the periodic table before it costs you points on test day.
How to Use the MCAT Periodic Table Efficiently on the Test Day
The MCAT is timed, so every second spent consulting the periodic table should be carefully managed so you score higher. Here’s how to use the table without losing time.
- Practice opening and closing the exhibit before test day: Know exactly where the button sits and how the pop-up window behaves for a smooth exam-day experience.
- Scan a question first to check if it actually needs the table: If the answer depends on trend reasoning, electron configuration, or something you should already know cold, opening the table won’t help, and it costs you time you didn’t need to spend.
- Anchor to known extremes instead of re-deriving every trend from scratch. Fluorine and francium sit at opposite ends of electronegativity and reactivity. Using them as reference points is faster than mentally rebuilding all four trend directions independently.
For exam calculations keep UWorld’s MCAT formula sheet on hand. It covers the equations you’ll need to know on test day.
| When to consult the table | When not to consult the table |
|---|---|
| To confirm an element’s exact atomic mass for stoichiometry calculations | To look up ionization energy or electronegativity values; neither is on the table |
| To verify atomic number when calculating neutrons (neutrons = mass number − atomic number) | To determine electron configuration, this must be derived, not looked up |
| To quickly locate an unfamiliar element's position and infer its group and period | To find a metal, nonmetal, or metalloid classification, the table has no labels or color-coding for this |
| To double-check a trend direction by comparing two elements’ positions, as a backup. |
Knowing what the periodic table won't tell you is just as important as knowing what it will. Bridging that gap between the table's raw data and the application you need for the exam is exactly what UWorld’s MCAT Prep Course is built for.
UWorld’s practice exams mirror the actual AAMC testing interface, including the exhibit button and periodic table pop-up so you can practice those crucial test-day mechanics. Beyond that, the QBank reinforces trend reasoning through exam-level passages with detailed visual explanations, while the books, video lessons and flashcards help lock in high-yield elements so your review sticks.
Frequently Asked Questions (FAQs)
Do you get a periodic table on the MCAT?
What does the MCAT periodic table include?
Is the periodic table available in every section of the MCAT?
Do you need to memorize element names for the MCAT?
Do you need to memorize periodic trends for the MCAT?
What’s the difference between atomic mass and mass number on the MCAT periodic table?
Can you bring your own periodic table to the MCAT?
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