An atom is the smallest particle of an element that is still that element.
Atom The smallest particle of an element.
Step 1: Something to Notice
Watch first. The explanation comes later.
Sodium reacts violently with water. Chlorine was used as a chemical weapon. Combine them and you get something you sprinkle on chips.
How can two dangerous elements make something harmless?
Step 2: Find Out
Watch what happens to particles when substances mix or change.
Step 1 — Predict
A compound of two dangerous elements — what properties will it have?
Choose what you think will happen. You cannot see the experiment until you do — guessing first is what makes it worth watching.
Step 3: So Here Is Why
Now the explanation, after you have seen it happen.
An element has only one kind of atom
There are about ninety naturally occurring kinds. Gold, oxygen, carbon, iron.
Element A substance made of only one kind of atom.
A compound is atoms bonded together
Two or more elements chemically joined, with properties of its own.
Compound Two or more elements chemically bonded, with new properties.
A mixture is not bonded
The parts keep their own properties and can be separated physically.
About a hundred kinds, and everything else is combinations
Every substance in the universe is built from around ninety naturally occurring elements. The enormous variety of materials comes from combinations, not from an enormous variety of ingredients.
Atoms and molecules
An atom is a single particle of an element; a molecule is two or more joined together. Oxygen gas is molecules of two oxygen atoms, which is why the distinction is not merely pedantic.
Step 4: A Common Mistake
Lots of people think
“A compound is a mixture of its elements, so it should behave a bit like both.”
Step 5: How Few Kinds There Are
The same idea somewhere new.
Everything you have ever touched is built from about ninety naturally occurring kinds of atom, and living things use barely a dozen of those in any quantity. The enormous variety of substances comes from combinations and arrangements, not from a large number of ingredients.
Step 6: Think It Through
Practice makes it stick.
Salt
Problem 1 of 2
Sodium is explosive and chlorine is poisonous. What is sodium chloride like?
Separating
Problem 2 of 2
Which can be separated by physical means alone?
Atoms, Elements, Compounds
1 of 4
What is an element?
2 of 4
Roughly how many naturally occurring elements are there?
elements
3 of 4
Does a compound have the properties of its elements?
4 of 4
What is the difference between a mixture and a compound?
Step 7: Quick Check
Show what you know.
Question 1 of 1
How can two dangerous elements make a harmless compound?
Step 8: Explain It in Writing
Claim, evidence, then reasoning.
The question
Explain how sodium and chlorine make something safe to eat, and what that shows about compounds.
Words to usebondednew propertiesmixtureseparatecombinedunrelatedsalt
Fill in all three boxes. The reasoning box is the one that matters most.
What You Found Out
- An atom is the smallest particle of an element.
- An element contains only one kind of atom; there are about ninety natural ones.
- A compound is elements chemically bonded, with properties of its own.
- A mixture is not bonded and keeps the properties of its parts.