SME
Grade 8 Science · Problem type
Reading an element’s group and period
Use this for “In which group and period is element 17?”
Diagram
Z = 8: Oxygen (O), group 16, period 2
This is an example. Type your own values to start a new problem.
Z
Atomic number
example
g
Group
worked out (not typed)
p
Period
worked out (not typed)
Formulas
g
=
the
group
of
element
Z
(group
=
the
group
of
element
atomic
number)
16 = the group of element 8
p
=
the
period
of
element
Z
(period
=
the
period
of
element
atomic
number)
2 = the period of element 8
Assumptions
•
The atomic number counts the protons in one atom and sets the element’s place.
•
Groups are numbered 1 to 18 across the top; periods 1 to 7 down the side.
•
The two rows under the table belong in periods 6 and 7 and have no group number here.
•
Tap an element to choose it.
Step-by-step
WE KNOW
Z = 8 (atomic number)
FIND
group (g), period (p)
Step 1 · Find group (g)
Use g = the group of element Z (group = the group of element atomic number)
Find the element on the table and read the number at the top of its column.
g
=
16
Step 2 · Find period (p)
Use p = the period of element Z (period = the period of element atomic number)
Find the element on the table and read the number at the start of its row.
p
=
2
Check
Put the numbers back in. Both sides should match.
16 = 16 ✓
2 = 2 ✓
Topic check
See what you know: 5 questions on this topic
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