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What did scientists model atoms as until the early 1900s?
Solid spheres
What is a model used for in science?
To explain observations and make predictions
What is an analogy?
A comparison between two things to help explain an idea
What analogy did the teacher use to describe atoms?
Atoms are like pool balls — solid spheres that hit each other but don’t change
Why are analogies useful in science?
They help us imagine things that are very small or very big
What did scientists in the early 1900s want to find out?
What is inside an atom
By 1932, what did scientists discover about atoms?
They are made up of tiny sub-atomic particles
What are the three types of sub-atomic particles?
Protons, neutrons, and electrons
Where are protons and neutrons found?
In the nucleus — the center of the atom
Where are electrons found?
They orbit outside the nucleus
What is the relative mass of a proton?
1
What is the relative mass of a neutron?
1
What is the relative mass of an electron?
1/2000
What is the relative charge of a proton?
+1
What is the relative charge of a neutron?
0 — no charge
What is the relative charge of an electron?
–1
