Atoms & Molecules
What is the smallest constituent unit of matter?
atom
What is the table that organizes all elements called?
Periodic Table
Which group conducts electricity well: metals or nonmetals?
Metals
What do we call a pure substance made of 2+ elements chemically combined?
A compound
A combination of substances not chemically bonded.
Mixture
What forms when atoms join together?
molecules
What is the chemical symbol for Oxygen?
O
What kind of color do nonmetals usually have?
Dull
Which subatomic particle has a positive charge?
proton
Is salt water a compound or a mixture?
Mixture
How much of an atom is empty space?
99.9%
What do elements contain only one type of?
Atom
Give one physical property of metals.
Shiny / ductile / malleable / conductor / solid
Which subatomic particle has almost no mass compared to others?
Electron
CO₂ is a compound. Name the two elements in it.
Carbon and Oxygen
Who first proposed the idea of “atomos”?
Democritus
Name any two noble gases.
He, Ne, Ar, Kr, Xe, or Rn
What is the most abundant element in Earth’s crust?
Oxygen
Molecules like O₂ and N₂ are what kind of pure substance?
Simple substances
Which can be separated by physical methods: mixtures or compounds?
Mixtures
What substance is formed by two hydrogen atoms and one oxygen atom?
Water (H₂O)
How many chemical elements are currently known?
118
Is gold a metal or nonmetal? And what is its symbol?
Metal - Au
What do we call atoms of the same element with different neutrons?
Isotopes
Identify: H₂ + O₂ → H₂O. What type of change is this?
Chemical change