What determines the order of elements on the periodic table?
AAlphabetical order of their names
BIncreasing atomic mass
CIncreasing atomic number
DThe year they were discovered
The modern periodic table arranges elements in order of increasing atomic number, which is the number of protons in the nucleus. Early versions used atomic mass, but atomic number turned out to be the true organizing principle.
Question 2 True / False
Elements in the same column of the periodic table tend to have similar chemical properties.
TTrue
FFalse
Answer: True
Columns (groups or families) contain elements with similar chemical behavior. For example, the elements in Group 1 (lithium, sodium, potassium, etc.) are all soft, reactive metals. This pattern of similar properties repeating in columns is what makes the periodic table 'periodic.'
Question 3 Short Answer
Who is credited with creating one of the first widely recognized versions of the periodic table?
Think about your answer, then reveal below.
Model answer: Dmitri Mendeleev.
In 1869, Russian chemist Dmitri Mendeleev published a periodic table that organized elements by atomic mass and left gaps for elements that had not yet been discovered. His predictions about the properties of those missing elements turned out to be remarkably accurate, validating the periodic table as a powerful organizing tool.