Atomic Structure
This is the smallest unit of an element that still keeps that element’s properties.
Atom
This is anything that has mass and takes up space.
Matter
A pure substance made of only one kind of atom.
Element
A change where new substances form.
Chemical change/reaction
A way to write a reaction using symbols, formulas, and an arrow.
Chemical equations
These are negatively charged particles found in the space around the nucleus.
Electrons
This is the amount of “stuff” in an object (not how big it is).
Mass
Two or more atoms bonded together.
Molecule
The starting substances in a reaction.
Reactants
In a chemical equation, what does the arrow (→) mean?
“Yields/produces” (reactants turn into products)
This positively charged particle is found in the nucleus.
Proton
This is how much space an object takes up.
Volume
The letters/numbers that show which elements are in a substance and how many.
Chemical formula
The substances made after a reaction.
Products
Identify the reactants and products in: 2H₂ + O₂ → 2H₂O
Reactants: 2H₂ and O₂
Product: 2H₂O
This particle has no charge and is found in the nucleus.
Neutron
Give two examples of physical properties (things you can observe without changing the substance).
Examples: color, texture, hardness, magnetism, melting point, boiling point
In H₂O, what does the small “2” mean, and what is it called?
It means 2 hydrogen atoms; it’s a subscript
A solid that forms when two liquids react.
Precipitate
In 2H₂O, how many total atoms are represented?
6 atoms (2 molecules × (2 H + 1 O) = 2 × 3)
Explain how atomic number and atomic mass are different.
Atomic number = # of protons
Atomic mass = protons + neutrons (mass number)
Name the three common states of matter and describe the shape/volume of each.
Solid (fixed shape, fixed volume)
Liquid (takes container’s shape, fixed volume)
Gas (takes container’s shape, fills container)
In 3CO₂, what does the “3” mean, and what is it called?
It means 3 molecules of CO₂; it’s a coefficient
This is the process where a metal (like iron) slowly reacts with oxygen/water and breaks down (like rusting).
Corrosion
Why do we use coefficients when writing equations instead of changing subscripts?
Coefficients change amount; changing subscripts changes the substance/formula (would make a different compound)