1. The Atom
Chapter 11 Section 2

2. Atoms An atom is so small…
atoms – the smallest particles into which an element can be divided and will remain the same substance
make up elements
often called the building blocks of matter
An atom is so small…
A penny contains
2 x 1022 atoms Or
20,000,000,000,000,000,000,000 atoms!
It would take a stack of 50,000 aluminum atoms to equal the thickness of a sheet of aluminum foil!

3. Parts of an Atom
BrainPOP
Atom
Even though an atom is tiny, it consists of even smaller parts/particles:
Nucleus
Electron Cloud
nucleus – small, dense, positively charged center of the atom
contains most of the atom’s mass
Particles inside the Nucleus:
Proton
Neutron
electron cloud – region around the nucleus of an atom where electrons are found
contains most of the atom’s mass
Particles outside the Nucleus:
Electron

4. Inside the Nucleus: Protons
protons - positively charged particles of the nucleus
All are identical
Each proton has an amu (atomic mass unit) of 1
Write/Say as: 1 amu

5. Inside the Nucleus: Neutrons
neutrons - particles of the nucleus that have no charge
All neutrons are identical
While neutrons are a bit larger than protons, they are not enough bigger to have a larger amu.
Neutron = 1amu

6. Outside the Nucleus: Electrons
electrons - negatively charged particles in atoms
around the nucleus within electron clouds
1st Level: 2 Electrons
2nd Level: 8 Electrons
3rd Level: 18 Electrons
charges of protons and electrons are opposite but equal in size
mass 1 proton ≈ 1800 electrons!
Electrons are so small the mass is usually considered to be zero! 2 8 18

7. Building Atoms Let’s build the simplest atom…the hydrogen (H) atom
Proton
Electron

8. Can we build bigger atoms?
Sure! Try this on your own paper…
A carbon atom has 6 protons, 6 neutrons, and 6 electrons or
An oxygen atom that has 8 protons, 9 neutrons, and 8 electrons

9. IN Activity: Summarize 3 – 2 – 1 Review!
On your output page:
3 Particles in an Atom
2 Main Parts of an Atom
1 The Building Blocks of Matter