Iron (?) vs Cobalt (?)
Place two elements side by side. Start from atomic number and position, then read the differences in the context of periodic trends rather than as isolated facts.
Z=26
Iron (?)
Begin with atomic number: it tells you how many protons are in the nucleus and therefore which element you are looking at.
Відкрити елемент →Z=27
Cobalt (?)
Begin with atomic number: it tells you how many protons are in the nucleus and therefore which element you are looking at.
Відкрити елемент →Mendeleev
Do not compare numbers without asking why they differ. Are the atoms in the same group? The same period? Has a new electron shell appeared? That is where the periodic table becomes an explanation rather than a list.