Answer:
group, chemical
Explanation:
In a periodic table, elements are arranged by electronic configuration, atomic number, and repeating chemical properties.
There are many properties of a periodic table and one of them is that "all the elements present in the same group have most similar chemical properties". This is so because the arrangement of valence electrons in a group is the same which gives the chemical properties to the elements.
For example: Lithium, sodium, potassium, and cesium belong to the same group and have the same chemical properties because they all have 1 valence electron.
Hence, the correct answer is "group, chemical".
