Groups, Periods and Locating Elements
You'll be able to identify groups and periods.
In 1869, Mendeleev grouped 63 elements into 8 columns, and every element in each column shares the same number of outer electrons.
Printable Worksheets
Print or save as PDF, or build a custom worksheet from any module's questions.
Q1 · How do you think the rows and columns of the periodic table are different from each other?
Q2 · Why do you think it's useful to know where an element sits on the periodic table rather than just knowing its name?
● Know
- groups are vertical columns
- periods are horizontal rows
- elements can be located by name, symbol or atomic number
● Understand
- position helps comparison
- the table layout is organised, not random
- you need navigation skill before pattern skill
● Can do
- identify groups and periods
- find elements from given information
- describe an element’s location clearly
Drop sodium into water and it fizzes violently; drop potassium in and it bursts into flame, both sit in the same vertical column of the periodic table, and that column is called a group. The horizontal rows are called periods. Groups contain elements with the same number of outer-shell electrons, which gives them similar chemical properties. Periods contain elements with the same number of electron shells. This two-way organisation turns the table from a simple list into a powerful prediction tool.
At this level, you do not need to memorise the whole table. You need to understand that position carries meaning: group number connects to valence electrons, and period number connects to electron shells.
Text description
- Group 1 column, highlighted: Li, Na, K, with H above; same properties.
- Period 2 row, highlighted: Li, Be, B, C, N, O, F, Ne; same electron shells (2).
- Mg, Al and Si are shown greyed in period 3.
- Group = same number of outer electrons, so similar chemical behaviour. Period = same number of electron shells.
Sodium (Na) sits in Group 1, Period 3. Its group tells us it has one valence electron and will react similarly to lithium and potassium. Its period tells us it has three electron shells. Without the table, we would have to memorise every element individually. With the table, we can predict behaviour from position.
Australian geoscience: Geoscience Australia uses the periodic table to classify minerals found in Australian ore deposits. By knowing an element's position, geologists can predict which other elements will be found nearby and guide mining exploration across the continent.
'The periodic table is just an alphabetical list of elements.' It is not. The order is by atomic number, and the arrangement into groups and periods reveals hidden patterns in chemical behaviour. The shape of the table is deliberate and meaningful, not decorative.
Tap each card to flip. Mark Got it when you can recall the answer without flipping.
The card above said that elements in the same period have the same number of electron shells. You can see why by building the atoms one at a time. The atomic number is the number of protons in the nucleus, and a neutral atom has the same number of electrons. So each element in the table has exactly one more proton and one more electron than the element before it.
In the shell (Bohr) model you met in Lesson 6, electrons sit in shells around the nucleus, and the shells fill from the inside out. For the first 18 elements the rule is simple: the first shell holds up to 2 electrons, the second up to 8, and the third takes the next 8. Hydrogen has 1 electron, written 1; helium has 2, which fills the first shell. Lithium's third electron cannot fit, so it starts a second shell: 2,1. The second shell keeps filling across period 2 until neon, 2,8. Sodium's eleventh electron starts a third shell, 2,8,1, and the third shell fills across period 3 until argon, 2,8,8.
Modelling atoms this way shows that atomic structure changes in a regular way as atomic number increases, and it explains two patterns in the table. The period number equals the number of occupied shells: lithium to neon have two, sodium to argon have three. And elements in the same group have the same number of electrons in their outer shell: lithium (2,1) and sodium (2,8,1) both have one, which is why they react in similar ways. Group 18 is the one exception in the first 18 elements: helium has only 2 electrons and neon and argon have 8, but all three have a full outer shell, and that shared feature is what the group has in common.
Text description
- Lithium (atomic number 3): 3 protons; electrons 2,1.
- Neon (atomic number 10): 10 protons; electrons 2,8.
- Sodium (atomic number 11): 11 protons; electrons 2,8,1.
Match each element to its electron arrangement.
- Oxygen (atomic number 8)
- Aluminium (atomic number 13)
- Argon (atomic number 18)
- Beryllium (atomic number 4)
- 2,8,8
- 2,2
- 2,6
- 2,8,3
Use the Element Locator interactive below. What is one thing you learned from using it?
Text description
- Period 1: H, He. Period 2: Li, Be, B, C, N, O, F, Ne. Period 3: Na, Mg, Al, Si, P, S, Cl, Ar.
- Metals: Li, Be, Na, Mg, Al. Metalloids: B, Si. Non-metals: H, He, C, N, O, F, Ne, P, S, Cl, Ar.
- Group = column (vertical); period = row (horizontal).
You can locate elements on the periodic table using several strategies. You can search by atomic number (the order of the table), by group (to find chemically similar elements), by period (to find elements with the same number of shells), or by category (metal, non-metal, metalloid). Each method gives different useful information.
The skill is choosing the right search strategy for your question. If you want similar chemical behaviour, search by group. If you want to know how many occupied electron shells an element has, search by period. If you want a general type of material, search by category.
Text description
- Groups (1 to 18) run across the top; periods run down the side.
- Na is where group 1 (G1) and period 3 (P3) meet.
- Group 1: 1 outer electron, so a reactive metal. Period 3: 3 electron shells.
If you need an element that conducts electricity and is malleable, you would look in the metal region on the left side of the table. If you need an element with similar properties to chlorine, you would look in Group 17, the halogens. Three of the columns are used by name often enough to be worth knowing: Group 1 are the alkali metals, so reactive that lithium, sodium and potassium all fizz or catch fire in water; Group 17 are the halogens, reactive non-metals such as fluorine, chlorine and bromine; and Group 18 are the noble gases, which are so unreactive that they combine with almost nothing, which is exactly why they are used inside light bulbs and neon signs where anything reactive would burn. The table supports multiple types of search, the best method depends on what you are trying to find out.
Australian mineral exploration: Mining companies use periodic table position to predict which valuable elements might be found together in Australian ore bodies. Elements in the same group often occur in similar geological settings, so the table guides where to drill and excavate.
'There is only one correct way to find an element on the table.' There are many valid ways. Scientists choose the search strategy that matches their question. A materials engineer and a geochemist might use completely different search methods on the same table, and both would be correct.
Drag each element into the correct group.
The periodic table provides a shared language for scientists worldwide. Instead of describing an element vaguely, chemists can say 'Group 2, Period 4' and every other chemist knows exactly which element and what properties to expect. This precision removes ambiguity and makes international collaboration possible.
This shared language is not just for professionals. It is the foundation of chemistry education everywhere. When you learn to use group and period numbers, you are learning to speak the same chemical language as scientists in every country.
Text description
- Li: Z = 3, period 2; reacts with water.
- Na: Z = 11, period 3; reacts vigorously.
- K: Z = 19, period 4; reacts very vigorously.
- All are in group 1, all have 1 outer electron, and all behave similarly with water.
A chemist in Perth and a chemist in Paris can both look up calcium and know it is an alkaline earth metal with two valence electrons. They do not need to describe its appearance or properties in words, the table position communicates everything essential. This is why the periodic table is called the 'chemist's address book.'
International science: The International Union of Pure and Applied Chemistry (IUPAC) maintains the official periodic table used by scientists in every country, including Australia. This shared reference ensures that chemical research, manufacturing standards and safety regulations are consistent globally.
'The periodic table is just a classroom poster.' It is far more than decoration. It is the central organising framework of chemistry, used daily by researchers, engineers, doctors and educators to predict properties and guide decisions. Every modern technology, from smartphones to medicines, relies on principles encoded in the periodic table.
Elements in the same have similar because they have the same number of outer .
Swap flashcards with a partner: one gives a symbol or atomic number, the other locates the element.
- Lithium (Li)
- Carbon (C)
- Neon (Ne)
- Group 14, Period 2
- Group 18, Period 2
- Group 1, Period 2
One of the biggest table-navigation errors is reversing rows and columns.
You should practise using the words group and period until the direction becomes automatic.
A strong answer also uses locating language accurately.
Choose five element boxes and state the group and period for each one using a classroom periodic table.
At the start of this lesson, you were asked about sodium and potassium both exploding in water and sitting in the same column of the periodic table, and what rows and columns actually tell us.
Now that you have worked through everything, write your answer below. How has your thinking changed, and what surprised you most?
Q1. Define group and period clearly.
Q2. Explain two different ways a student could locate an element on the periodic table.
Q3. Why is it helpful to describe an element by its position as well as its name?
Model answers (click to reveal)
Model Answers
-Multiple Choice
1: A. A group is a vertical column.
2: B. A period is a horizontal row.
3: D. Name, symbol and atomic number can all help locate an element.
4: C. Positional language gives a precise way to describe location.
5: A. That statement reverses groups and periods.
Short Answer 1
A group is a vertical column in the periodic table. A period is a horizontal row in the periodic table.
Short Answer 2
A student could locate an element using its symbol or using its atomic number. Either type of information can be matched to the correct element box on the periodic table.
Short Answer 3
It is helpful because position gives precise scientific language for locating and comparing an element. It also makes later pattern discussions clearer.
Model answers (click to reveal)
Model Answers
-Multiple Choice
1: A. A group is a vertical column.
2: B. A period is a horizontal row.
3: D. Name, symbol and atomic number can all help locate an element.
4: C. Positional language gives a precise way to describe location.
5: A. That statement reverses groups and periods.
Short Answer 1
A group is a vertical column in the periodic table. A period is a horizontal row in the periodic table.
Short Answer 2
A student could locate an element using its symbol or using its atomic number. Either type of information can be matched to the correct element box on the periodic table.
Short Answer 3
It is helpful because position gives precise scientific language for locating and comparing an element. It also makes later pattern discussions clearer.
● Group
Vertical column.
● Period
Horizontal row.
● Locate
Elements can be found by name, symbol or atomic number.
● Next
The next lesson introduces metals, non-metals and metalloids.