4 mistakes learners make with the periodic table, each one named and explained.
The group number tells you the outer electrons, and the outer electrons decide the reactions.
Eight is given as the number of outer electrons whatever group the element is in.
Eight is the number stressed most often, because a full shell is what everything is trying to reach.
Question. Group 2
A common answer. 8 outer electrons
The answer. 2 outer electrons
Why. Eight is what the atom wants, not what it has.
Reactivity comes from the gap between the two. If they were equal, nothing would react.
An element in Group 2, Period 3 is given three outer electrons.
Two numbers are offered and only one of them is the right one to use.
Question. Group 2, Period 3
A common answer. 3 outer electrons
The answer. 2 outer electrons
Why. The group number gives the outer electrons; the period gives the number of shells.
Group is across, and it is the one that decides the chemistry.
Elements in a group are said to behave alike because they have similar masses.
Mass is printed on every box in the table, so it is the most visible number.
Question. Why a group behaves alike
A common answer. they have similar masses
The answer. they have the same number of outer electrons
Why. Lithium and caesium behave alike and their masses are wildly different.
Chemistry is decided by the outer electrons. Mass decides almost nothing about reactions.
A Group 2 element is given one outer electron.
The columns are counted from the wrong end, or the group is read off a neighbouring column.
Question. Group 2
A common answer. 1 outer electron
The answer. 2 outer electrons
Why. The group number is the number of outer electrons, directly.
For the main groups the number is the answer. No calculation is needed.
WAJD spots these patterns in your child's answers and names the one behind their wrong answers, instead of just marking them wrong.