Key Scientists
Who is known as the “father of the periodic table”?
Dmitri Mendeleev
What does “workability” mean in science?
How well a theory or model explains and predicts what we observe.
What does it mean when we say the periodic table has “predictive power”?
It can be used to predict properties of unknown or undiscovered elements.
What are the horizontal rows on the periodic table called?
Periods
What particle determines an element’s atomic number?
Protons
This scientist arranged the periodic table by atomic number instead of atomic mass.
Henry Moseley
Why was Mendeleev’s table considered “workable” even with gaps?
It correctly predicted properties of yet-undiscovered elements.
How did Mendeleev prove his table had predictive power?
He accurately described undiscovered elements’ properties.
What are the vertical columns on the periodic table called?
Groups or Families
Why do elements in the same group have similar reactivity?
They have the same number of valence electrons.
Which scientist discovered that elements’ properties repeat periodically when arranged by atomic mass?
Dmitri Mendeleev
What problem with earlier tables did Mendeleev’s version fix?
He left spaces for missing elements and grouped by properties, not just mass.
What modern use of the periodic table shows its predictive power?
Predicting chemical behavior and bonding trends in new compounds.
Elements in the same group have what in common?
Similar chemical properties and number of valence electrons.
As you move across a period, what happens to atomic number?
It increases by one for each element.
Who developed the triad system to group elements with similar properties?
Johann Döbereiner
How did Moseley’s discovery improve the table’s workability?
It explained inconsistencies by arranging elements by atomic number.
Why are trends like electronegativity and ionization energy predictable?
Because they follow periodic patterns related to atomic structure.
What group is known as the noble gases?
Group 18
How does the periodic table reflect electron energy levels?
Each period corresponds to a new principal energy level.
What contribution did Henry Moseley make that changed how we organize the periodic table today?
He discovered atomic number, leading to reorganization by number of protons instead of mass.
Give an example of an element Mendeleev predicted before it was discovered.
Gallium or Germanium
How does the periodic law summarize the table’s predictive power?
It states that element properties repeat periodically when arranged by atomic number.
Which family is the most reactive group of nonmetals?
Halogens (Group 17)
Explain how the periodic table’s arrangement helps us understand atomic structure.
It shows patterns in electron configuration, energy levels, and chemical behavior.