7th grade · Science · Unit 1 of 18
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.
Texas Essential Knowledge and Skills (TEKS) teks student expectation: 7.6(A); 7.6(B) · elements and compounds, chemical symbols and formulas, and the periodic table
How we explain it
Children can open this short lesson before they practice.
- An element has only one kind of atom. A compound has two or more elements joined chemically. A mixture is substances mixed but not joined.
- Rows of the periodic table are periods; columns are groups. Metals are on the left, non-metals on the right.
- In a formula, the small number after a symbol counts the atoms just before it.
Example: How many atoms are in one molecule of H₂O? H₂ means 2 hydrogen atoms. O with no number means 1 oxygen atom. 2 + 1 = 3. Answer: 3
Atoms & Elements in Texas
In the Texas Essential Knowledge and Skills (TEKS), this is unit 1 of 18 in 7th grade Science, before Physical or Chemical?.
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: Texas Education Agency (TEA)
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
Elements in the same column (group) of the periodic table…
- all have the same mass
- have similar chemical properties
- are all gases
- were all discovered in the same year
have similar chemical properties
Hint: Groups are like families: sodium and potassium, in the same group, both react strongly with water.
Question 2
What are the horizontal rows of the periodic table called?
- groups
- periods
- families
- symbols
periods
Hint: Rows run across and are called periods. Columns run up and down and are called groups (or families).
Question 3
Which element has the chemical symbol Mg?
Mgchemical symbol- sodium
- magnesium
- manganese
- mercury
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 4
Which property is typical of a solid non-metal, such as sulphur?
- dull and brittle
- shiny and bendable
- easy to hammer into thin sheets
- a good conductor of electricity
dull and brittle
Hint: Non-metals are usually poor conductors, and as solids they tend to be dull and break easily.
Question 5
Which particles are found in the nucleus (center) of an atom?
- only electrons
- electrons and protons
- protons and neutrons
- neutrons and electrons
protons and neutrons
Hint: Electrons move around the outside of the nucleus. Protons and neutrons are packed in the center.
Question 6
How many different elements are in H₂O₂ (hydrogen peroxide)?
H₂O₂hydrogen peroxideanswer box
2
Hint: Each capital letter starts a new element symbol. Count the different symbols, not the small numbers.