Next Generation Science Standards

Performance Expectation

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.

Want to hear a joke about potassium?

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Don't worry, we only make bad science puns periodically. Once your students are done with this performance expectation, they'll be making periodic table puns left and right. They'll also understand how to use the periodic table to predict the properties of elements based on their valence electrons. Who said all the good chemistry jokes argon?

Here are some elementary activity ideas to tackle this performance expectation:

• Divide up the periodic table so each student gets a main group element. Then have them create a trading card. You know, like a baseball card, or a Pokémon card, or whatever it is kids are trading these days. The card should have information about their element, including atomic number, atomic mass, symbol, number of valence electrons, and any important properties. Then have students mingle around with one another and compare notes. What elements might their element have a fiery romance (i.e. reaction) with? What elements are super similar to theirs, and why?
• Introduce students to the wonder of Bohr diagrams and Lewis dot structures using something fun and edible, like M&M's to represent the electrons. If you don't feel like dealing with a bunch of hyperactive teenagers, choose your favorite circular, whole-grain cereal. Have students randomly select ten or so elements from the periodic table (if you want to turn it into a darts situation, that's up to you) and draw the Bohr diagram and Lewis dot structure for each using their edible electrons. Then you feast!
• Play Guess Who, periodic table-style. Partner the students up and provide them with a deck of element cards (they can just cut the main group elements out of a periodic table if you're not in the mood for making a laminated craft project out of this). Each partner will select one element that the other will try to guess. They will take turns asking yes or no questions to gather clues and eliminate elements that don't match the description until they've narrowed it down to guess the correct element.

Disciplinary Core Ideas

PS1.A – Structure and Properties of Matter: Each atom has a charged substructure consisting of a nucleus, which is made of protons and neutrons, surrounded by electrons.

Before students can cannonball into mastering the periodic table's predictive abilities, they need to know a little atom anatomy (say that five times fast). This disciplinary core idea is pretty straightforward for this one: students just need to know that an atom has a positively charged nucleus, which contains the protons and neutrons, and negatively charged electrons around the nucleus.

To tap into the predictive abilities of the periodic table, a little extra understanding of how valence shells keep those electrons organized will go a long way. Students should know that the innermost shell holds up to two electrons, while each subsequent shell can carry up to eight electrons.

Your students have heard about atoms and their parts before, so they'll probably just need a little refresher on where the protons, neutrons, and electrons are located and what their charges are. After that, a little independent practice should help them get the hang of identifying each of those subatomic particles.

PS1.A – Structure and Properties of Matter: The periodic table orders elements horizontally by the number of protons in the atom's nucleus and places those with similar chemical properties in columns. The repeating patterns of this table reflect patterns of outer electron states.

Think about how you organize the clothes in your closet. Do you arrange everything by color? By season? By fanciness? By least-to-most stains/holes? Just like there are many ways to keep your wardrobe in order, there are many ways to organize the elements in the periodic table.

After a lot of explaining, arguing, and perhaps some fisticuffs, scientists settled on putting atoms in order from least to greatest number of protons. This is the first thing students need to know about the periodic table: the number of protons is indicated by the atomic number on the periodic table.

Students should also know that each column on the table has elements with the same number of valence electrons. Since the number of valence electrons says a lot about the properties of that element, we observe similar properties for elements in the same column, such as reactivity or types of bonds formed. This is why we sometimes call the columns "groups" or "families."

For example, noble gases have a complete set of eight electrons in their outer shell, which makes them very Zen and unlikely to react with other elements. All of the elements in this column are relatively non-reactive.

If we skip over to the opposite side of the periodic table and take a look at the alkali metals, we've got a whole different group. These atoms are a sassy bunch that like to react with anything and everything, even water.

Students may struggle to get the hang of the patterns of the periodic table, but once it becomes second nature, they'll totally appreciate how well organized it is. Also, they really only need to be familiar with the main group elements (sorry Ytterbium), which should make recognizing patterns much easier.

Learning the properties of all the columns on the periodic table can be a lot to tackle solo, so consider assigning different columns to different students (or teams of students), having them research the properties of that "family," and then sharing with the rest of the class.

PS2.B – Types of Interactions: Attraction and repulsion between electric charges at the atomic scale explain the structure, properties, and transformations of matter, as well as the contact forces between material objects. (Secondary to HS-PS1-1)

Atoms are made up of subatomic particles that have multiple personalities. Students should know that the electrons carry a negative charge, protons a positive charge, and neutrons carry no charge. The number of each of these particles determines whether that atom is a social butterfly that is likely to react with anything, or on the shy, nonreactive side.

Students should also know that atoms aren't always the best at keeping track of their electrons. When they lose an electron, the atom becomes a negatively charged anion. When they gain one, the atom becomes a positively charged cation. These overall changes in electric charge affect how that atom will bond with other atoms, as well as the properties of the molecules and structures it will eventually create.

Students really only need to focus on the general relationship between the differently charged particles within an atom and between multiple atoms. Don't try and make them calculate ionization energies unless you want them to plot a coup against you in-between periods.

As long as students have a basic grasp of atomic structure and patterns in valence electrons in the periodic table, they shouldn't be too flummoxed by this idea. It may be difficult for them to visualize the relationship between electric charges at the atomic scale and the resulting material object, but simulations and small group discussions are great ways to counteract confusion.

Science and Engineering Practices

Developing and Using Models: Use a model to predict the relationships between systems or between components of a system.

The periodic table is an amazing model, but you'll never see it strutting its stuff down the catwalk, so most students don't even realize it's a model. Students will use the patterns they've observed in the periodic table, along with what they know about atoms and valence electrons, to predict which elements share similar properties, like reactivity with oxygen or the types and numbers of bonds they're able to form. Surprise, this is using the modeling capabilities of the periodic table.

Crosscutting Concepts

Patterns: Different patterns may be observed at each of the scales at which a system is studied and can provide evidence for causality in explanations of phenomena.

The periodic table would look like a Magna Doodle in the microwave if it weren't for patterns. Students should understand that every time they organize something, whether it's the clothes in their closet or their notes for history class, they are looking for patterns and using those patterns to make sense of a big mess.

Students should understand that scientists looked for patterns in valence electrons and how elements behave to help them organize the periodic table. What they came up with may look a little funny, but is actually a really great way to understand the relationships between the different elements.