DIRECTIONS: Here the elements are in order of proton count. Read down a column, then across a row.
Elements in the same column behave alike: far right, gases that react with almost
nothing; far left, metals so reactive they are kept under oil.
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Question
Your answer
1.
name two elements that should behave like sodium (Na)
2.
name two that should behave like neon (Ne)
3.
which column would you expect to be the least reactive of all
The Gaps Are the Evidence
Grade 8 · Atoms · Page 2 of 3
DIRECTIONS: In 1869 Mendeleev's table only worked if he left holes. Read, then answer.
He said the gaps were undiscovered elements and predicted them from their
neighbors. For one: density about 5.5, low melting point. Six years later gallium was found: density 5.9, and it
melts in your hand.
Closing the gaps would have made a neater table. Say why leaving them was the better science.
A tidy arrangement of things already known is not strong evidence on its own. Say what the gallium prediction adds that tidiness cannot.
How could Mendeleev say anything at all about an element nobody had ever seen? Answer using the columns from page 1.
Using the Order
Grade 8 · Atoms · Page 3 of 3
DIRECTIONS: Use the table to answer questions about elements you have never met.
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The question
Your answer, and how the table gets you there
7.
rubidium (Rb) sits below potassium (K). Would you expect it to react with water gently or violently?
8.
argon (Ar) is used to fill light bulbs. Which column is it in, and why does that make it a good choice?
9.
a new element is made in a laboratory with 119 protons. Say roughly where it goes and why
Explain in a sentence why the table is called periodic — what is it that repeats?