Grade 8 · Atoms, Elements and the Periodic Table · Atomic Structure
Inside the Atom
Protons, neutrons, electrons and how we model the atom.
Learning objectives
- Identify the three subatomic particles and their charges.
- Explain why an atom is normally neutral.
- Use atomic number and mass number to describe an atom.
NGSS alignment
HS-PS1-1
Use the periodic table as a model to predict the relative properties of elements based on the patterns of electrons in the outermost energy level of atoms.
MS-PS1-1
Develop models to describe the atomic composition of simple molecules and extended structures.
HS-PS1-8
Develop models to illustrate the changes in the composition of the nucleus of the atom and the energy released during the processes of fission, fusion, and radioactive decay.
MYP criteria
- Criterion A — Knowing and Understanding
ENGAGE
What is inside an atom?
Think about it
Atoms are mostly empty space. So what actually gives an atom its mass and its identity?
EXPLAIN
Subatomic particles
| Particle | Location | Relative charge | Relative mass |
|---|---|---|---|
| Proton | Nucleus | 1+ | 1 |
| Neutron | Nucleus | 0 | 1 |
| Electron | Shells around nucleus | 1- | 1/1836 |
- Atomic number = number of protons = the element identity.
- Mass number = protons + neutrons.
- Neutral atom: protons = electrons.
Watch
Atomic Structure Explained
TED-Ed · 5:20
It builds the atom piece by piece so you can see where mass and charge come from.
Before you watch: Before watching: what do you think is inside an atom?
- What are the three main subatomic particles?
- Which particle determines the element?
- Why is an atom normally electrically neutral?
Interactive simulation · PhET
Isotopes and Atomic Mass
Build different isotopes of the same element and compare their masses.
While you explore
- What changes between isotopes of one element?
- Why is atomic mass not a whole number?
Key vocabulary
- Atomic number
- The number of protons in an atom - it tells you which element it is.
Practice questions
0/2 correct
Level 1
Which subatomic particle has a negative charge?
Level 2
An atom has 17 protons and 18 neutrons. What is its mass number?
Reflect & track
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