9th grade · Science · Unit 6 of 10
The Periodic Table
Groups, periods and patterns
What your child practices
Groups and periods, metals, non-metals and metalloids, alkali metals, halogens and noble gases, and how valence electrons and shells explain the patterns.
Arizona Academic Standards learning standard: HS.P1U1.1 · patterns in the periodic table
How we explain it
Children can open this short lesson before they practice.
- Rows are periods; the number of electron shells gives the period.
- Columns are groups. In groups 1 and 2, the group is the number of valence (outer) electrons; for groups 13 to 18, add 10.
- Group 1: alkali metals; group 17: halogens; group 18: noble gases, which rarely react.
Example: Oxygen’s electrons are 2, 6. Which period and group is it in? 2 shells: period 2. 6 valence electrons: 6 + 10 = group 16. Answer: period 2, group 16
The Periodic Table in Arizona
In the Arizona Academic Standards, this is unit 6 of 10 in 9th grade Science, after Photosynthesis & Respiration and before Chemical Change.
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
Chlorine has electrons arranged 2, 8, 7. Which period (row) is it in?
answer box
3
Hint: The number of occupied shells is the period number: 3.
Question 2
Which pair is likely to have the most similar chemical properties?
- carbon and neon
- oxygen and magnesium
- sodium and chlorine
- sodium and potassium
sodium and potassium
Hint: Both are in Group 1.
Question 3
Which element has 3 electron shells and 5 valence electrons?
- Phosphorus
- Lithium
- Beryllium
- Boron
Phosphorus
Hint: 3 shells puts it in period 3, and 5 valence electrons places it in group 15: that is phosphorus.
Question 4
Which pattern is shown by atomic number across the periodic table?
- It increases by one from each element to the next
- It is the same in a group
- It decreases across a period
- It goes up by two each time
It increases by one from each element to the next
Hint: Each element has one more proton than the one before.
Question 5
Lithium has electrons arranged 2, 1. Which group (column) number is it in?
answer box
1
Hint: The outer shell has 1 valence electrons. For this element that means Group 1 (groups 13 to 18 have 3 to 8 valence electrons).
Question 6
Where are the metals found on the periodic table?
- only in the top row
- metals are not on the table
- only on the far right
- on the left and in the middle
on the left and in the middle
Hint: Most elements are metals. Non-metals are mostly on the right.