Learning objective 2: I can understand the patterns found in the number of protons, neutrons, and electrons in an atom.

What is everything made out of? What can something be made of?

Each different type of atom is called an element, and they are organized into a table… The Periodic Table of the Elements contains every possible atom so far discovered.

Using the periodic table

The atomic number tells you how many protons are in that atom Protons are the identity of an atom, adding or subtracting protons gives you a different element

So, we know carbon has 6 protons. How many electrons does it have? It must have 6, because an atom is always neutral. So the atomic number is really the number of protons and also the number of electrons

Atomic mass is how much mass the atom has. How can we use this?

Subatomic Particle Charge Location Size/Weight Proton Positive (+) Nucleus or “Core” Large/1 au Neutron No Charge (0) Electron Negative (-) Electron Cloud Small/0 au

Protons and neutrons are the only parts that have any mass, so the atomic mass is the number of protons and neutrons added up.

Atomic weight (rounded) — number of protons = number of neutrons So, there are 6 protons, weighing 1 au each. How many neutrons must there be? Atomic weight (rounded) — number of protons = number of neutrons 12 total — 6 protons = 6 neutrons Note: the numbers of protons and neutrons won’t always be equal

Sometimes, the element’s box won’t look quite the same

It may look like this… Atomic number Symbol Atomic mass Name

Name Atomic number Symbol Atomic mass

Atomic number Symbol Name Atomic mass Don’t worry about this, you’ll learn it in high school Symbol Name Atomic mass

Time for some practice!