6th grade · Science · Unit 2 of 9
Atoms & Elements
Elements, compounds and chemical symbols
What your child practices
Elements versus compounds and mixtures, chemical symbols (H, O, Na, Cl, Fe, Au…), counting atoms in formulas like H₂O and C₆H₁₂O₆, metals and non-metals, and the basics of the periodic table.
Arizona Academic Standards learning standard: 6.P1U1.3 · matter made of atoms
How we explain it
Children can open this short lesson before they practice.
- An element is a pure substance made of only one type of atom, like gold (Au).
- A compound is two or more elements chemically joined, like table salt (NaCl).
- A mixture is substances mixed but not joined, like air or soil.
- To count atoms in a formula, add the small numbers. No number means 1.
Example: How many atoms are in one H₂SO₄? H₂: 2 atoms. S: 1 atom. O₄: 4 atoms. 2 + 1 + 4 = 7. Answer: 7
Atoms & Elements in Arizona
In the Arizona Academic Standards, this is unit 2 of 9 in 6th grade Science, after Particles and Heat and before Fields & Forces at a Distance.
Gradelings describes a child's practice on this unit as Beginning, Approaching, Meeting or Exceeding (Four practice steps). That reflects practice, not a report-card mark: the teacher decides the mark.
Source: Arizona Department of Education
Sample questions
A taste of this unit. In the app, questions change every time and get easier or harder to match your child.
Question 1
Which statement about compounds is true?
- Every compound contains a metal
- A compound always has the same elements in the same proportions
- A compound can have a different recipe each time it forms
- A compound has only one kind of atom
A compound always has the same elements in the same proportions
Hint: Water is always 2 hydrogen atoms to 1 oxygen atom, whether it's in a lake or a glass.
Question 2
Which element has the chemical symbol Mg?
Mgchemical symbol- mercury
- magnesium
- manganese
- sodium
magnesium
Hint: Most symbols are the first one or two letters of the name (O for oxygen, Ca for calcium). Some come from Latin names: Na (natrium) for sodium, Fe (ferrum) for iron, Au (aurum) for gold, Ag (argentum) for silver, K (kalium) for potassium, Pb (plumbum) for lead, Hg (hydrargyrum) for mercury, Sn (stannum) for tin.
Question 3
Element, compound or mixture? Sort each substance.
Sort into: ⚛️ element · 🧪 compound · 🥣 mixture
- 🧂table salt (NaCl)
- 🪴garden soil
- 💎diamond (pure carbon, C)
- 🥜trail mix
- 🍬table sugar (C₁₂H₂₂O₁₁)
- 🎈helium (He)
⚛️ element: diamond (pure carbon, C), helium (He) · 🧪 compound: table salt (NaCl), table sugar (C₁₂H₂₂O₁₁) · 🥣 mixture: garden soil, trail mix
Hint: An element has only one kind of atom. A compound has different elements chemically joined in a fixed ratio. A mixture is substances mixed together but not chemically joined.
Question 4
What is the chemical symbol for sulphur?
⚛️sulphur- S
- Su
- Sf
- Sl
S
Hint: Most symbols are the first one or two letters of the name (O for oxygen, Ca for calcium). Some come from Latin names: Na (natrium) for sodium, Fe (ferrum) for iron, Au (aurum) for gold, Ag (argentum) for silver, K (kalium) for potassium, Pb (plumbum) for lead, Hg (hydrargyrum) for mercury, Sn (stannum) for tin.
Question 5
How many atoms in total does the formula C₃H₈ (propane) show?
C₃H₈propaneanswer box
11
Hint: A small number after a symbol tells how many of that atom there are. A symbol with no small number means 1. Add them all up.
Question 6
Which element is a noble gas that almost never reacts with other elements?
- neon (Ne)
- iron (Fe)
- chlorine (Cl)
- sodium (Na)
neon (Ne)
Hint: Noble gases sit in the far right column of the periodic table. They glow in signs but rarely form compounds.