HS-PS1-1: Reading the Periodic Table to Predict Properties
Also called NGSS HS-PS1-1 · Topic: Structure and Properties of Matter · Physical Science
The Official Wording
Use the periodic table as a model to predict the relative properties of elements based on the patterns of electrons in the outermost energy level of atoms.
Clarification statement: Examples of properties that could be predicted from patterns could include reactivity of metals, types of bonds formed, numbers of bonds formed, and reactions with oxygen.
Assessment boundary: Assessment is limited to main group elements. Assessment does not include quantitative understanding of ionization energy beyond relative trends.
NGSS Lead States, 2013 · Read it on nextgenscience.org · checked October 15, 2026
What HS-PS1-1 Means in Plain English
High school students use the periodic table as a map of electron arrangements. Knowing how many valence electrons an element has, and how far they sit from the nucleus, lets them predict how reactive a metal is, which bonds it forms and how many.
The work stays with the main group elements and with trends described as higher or lower, not ionization energies in kilojoules. It builds on middle school atom models (MS-PS1-1) and feeds straight into explaining reaction outcomes (HS-PS1-2).
HS-PS1-1 I Can Statements
- I can find an element's valence electrons from its group number.
- I can predict which of two metals reacts more strongly and say why.
- I can predict how many bonds a main group atom usually forms.
HS-PS1-1 Worked Example
A ranking lesson built around a short teacher demonstration video of three group 1 metals.
Can the periodic table predict which of lithium, sodium and potassium reacts most violently with water?
Set It Up: A periodic table, a demonstration video of each metal dropped into water with indicator, and a prediction sheet.
- Find all three metals in group 1 and note each has one valence electron.Li, Na, K: one valence electron each
- Count the energy levels for each atom going down the group.Li 2 levels, Na 3, K 4
- Rank them from least to most reactive before watching.Guess: Li < Na < K
- Watch the video and record fizzing, speed and any flame for each metal.Li fizzes, Na skates and melts, K ignites with a lilac glow
- Compare the order in the video with the guess.Order matches the guess
Reactivity rose going down the group, from lithium to sodium to potassium, just as the table pointed to.
Why it works: Further down the group, the lone valence electron sits farther from the nucleus and is shielded by more inner electrons, so removing it takes less energy.
Common Mistakes with HS-PS1-1
Thinking bigger atoms hold electrons tighter
“Potassium has more protons, so it should keep its electron better.”
Try this: More protons are offset by more inner electron shells. The outer electron is farther away and shielded, so the pull on it is weaker.
Applying metal trends to nonmetals
Predicting iodine is more reactive than fluorine because it is lower
Try this: Nonmetals react by gaining electrons, so the trend flips. Fluorine, small and near the top, attracts an extra electron most strongly.
Counting all electrons instead of valence ones
Saying sodium bonds like it has 11 electrons to share
Try this: Only the outermost electrons take part in bonding. For main group elements, the group number tells you how many there are.
Where HS-PS1-1 Fits
Practice HS-PS1-1
Quick Check
- How many valence electrons does magnesium have, and how do you know?
- Which is more reactive, calcium or barium?
- How many bonds does carbon usually form?