These questions ask you to identify rows and columns, use their numbering, connect certain columns with family names, and place the detached lower rows correctly. Begin with direction, then apply the relevant number or family fact.
Separate the two directions
A group runs vertically, with elements above and below one another. A period runs horizontally, from left to right. A simple imaginary movement helps: moving down stays in one group, while moving across stays in one period. In the modern numbering used here, groups run from 1 to 18 and there are seven periods. Group numbers therefore increase across the table rather than down it.
| Signal | Table feature or fact |
|---|---|
| Vertical column | Group |
| Horizontal row | Period |
| First period | Two elements |
| Second or third period | Eight elements in each |
| Metallic members of group 1 | Alkali metals; hydrogen is excluded from that classification |
| Group 2 | Alkaline-earth metals |
| Group 17 | Halogens |
| Group 18 | Noble gases |
| Lanthanides printed below | Part of period 6 |
| Actinides printed below | Part of period 7 |
Use the numbering as a map. Group 18 is the final numbered column, group 17 is just before it, and group 2 follows group 1 as you move across. The two long rows often printed below the main rectangle are folded out only to save width. Imagine inserting them into their proper rows before deciding their period.
Where table-reading mistakes come from
| Tempting route | How to reject it |
|---|---|
| Calling a row a group or a column a period | Trace the direction before naming the feature. Across means period; down means group. A single cell is only one position, not a whole row or column. |
| Using 18 for periods or 7 for groups | Keep the dimensions as a pair: 18 vertical groups and seven horizontal periods. Do not transfer a count from one direction to the other. |
| Confusing neighbouring family names | Anchor the sequence: group 1 metals are alkali metals, group 2 is the alkaline-earth family, group 17 contains the halogens, and group 18 contains the noble gases. |
| Treating a detached lower line as an extra period | Printing position is not structural membership. Reinsert the lanthanides into period 6 and the actinides into period 7. |
Try it
A counter advances once for each distinct proton count represented by an element in period 1. A learner guesses 8 and another guesses 18. How many advances does it actually make? Enter the number.
Which statements correctly classify group 2? Select all that apply.
- Its elements are alkaline-earth metals.
- Its elements are the alkali-metal family.
- It is the column immediately after group 1.
- It is the halogen family.
- It is the transition-metal family.
A student treats the detached actinide line as an eighth row. Which placement fixes this groups-and-periods error?
- It belongs within period 7.
- It belongs within period 6.
- It forms period 8.
- It has no period assignment.