DIRECTIONS: There are about ninety kinds of atom. What makes one kind different from another? Read, then answer.
An atom has a tiny, heavy center of protons and neutrons,
with electrons around it. The number of protons decides the kind: 1 is hydrogen, 6 carbon, 79 gold.
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If the center holds…
Which kind is it?
How do you know?
1.
1 proton
2.
6 protons
3.
6 protons and 8 neutrons instead of 6
4.
8 protons
Row 3 is the interesting one. Say what changed and what did not, and why the kind stayed the same.
How Anybody Knows
Grade 8 · Atoms · Page 2 of 3
DIRECTIONS: Nobody has seen inside an atom. Read the 1909 experiment, then answer.
Fast, heavy particles were fired at thin gold foil. Nearly all went
straight through. About one in eight thousand came back.
What does "nearly all of them went straight through" tell you about an atom?
What does the tiny number that bounced straight back tell you? Say why "small" and "heavy" both follow.
science-11-grade6 sheet 30 works out the inside of a planet from earthquake waves that never arrive. Say what the two investigations have in common.
Mostly Nothing
Grade 8 · Atoms · Page 3 of 3
DIRECTIONS: If an atom's center were a marble in the middle of a football field, the atom would reach the stands.
So a table is almost entirely empty space. Your hand stops because the
electrons of one atom push hard on the electrons of the next.
A friend says solids feel solid because their atoms are packed with no gaps. Using this page, say what is wrong and what actually holds your hand up.
Almost all of an atom's mass is in that tiny center. Explain how something so small can be nearly all of the weight.
Say what you would have concluded in 1909 if every single particle had gone straight through with none coming back.