What is the relative charge of a proton?
+1
What did scientists model atoms as until the early 1900s?
Solid spheres
Why do atoms have no overall electric charge?
Because the number of protons equals the number of electrons
Where are electrons found?
They orbit outside the nucleus
What is the relative charge of an electron?
–1
What is an analogy?
A comparison between two things to help explain an idea
What did scientists in the early 1900s want to find out?
What is inside an atom
Where are protons and neutrons found?
In the nucleus — the center of the atom
What is the analogy comparing the size of the nucleus to the atom?
If the atom were the size of a football stadium, the nucleus would be the size of a pea
By 1932, what did scientists discover about atoms?
They are made up of tiny sub-atomic particles
What does that analogy tell us about atoms?
Atoms are mostly empty space
If an atom has 5 protons (+5) and 5 electrons (–5), what is its overall charge?
0 — neutral
What analogy did the teacher use to describe atoms?
Atoms are like pool balls — solid spheres that hit each other but don’t change
What is the relative mass of an electron?
1/2000
What is a model used for in science?
To explain observations and make predictions
Why are analogies useful in science?
They help us imagine things that are very small or very big
Nearly all the mass of an atom is found where?
In its nucleus
What is the relative charge of a neutron?
0 — no charge
If an atom has 4 protons (+4) and 4 electrons (–4), what is its charge?
0 — neutral
What is the relative mass of a neutron?
1
What is found at the center of every atom?
The nucleus
What force holds the atom together?
The attraction between the positive nucleus and negative electrons
What is the relative mass of a proton?
1
What are the three types of sub-atomic particles?
Protons, neutrons, and electrons