Unit 2: Periodic Properties Flashcards
(32 cards)
Who first proposed the periodic law based on increasing atomic mass?
Dmitri Mendeleev and Lothar Meyer in 1869.
What did Henry Moseley change about the periodic table in the 1930s?
He rearranged it based on atomic number instead of atomic mass.
What are the vertical columns in the periodic table called?
Groups.
What are the horizontal rows in the periodic table called?
Periods.
What quantum number determines the principal energy level?
The principal quantum number (n).
What happens to the principal quantum number as you move down a group?
It increases.
Why do elements in the same group have similar chemical properties?
They have the same number of valence electrons.
What do we call electrons in the outermost energy level?
Valence electrons.
What type of electrons are included as valence electrons in transition metals?
The outermost d electrons in addition to the highest n level electrons.
What is atomic radius?
The average distance from the nucleus to the outer boundary of the electron cloud.
What happens to atomic radius across a period?
It decreases.
What happens to atomic radius down a group?
It increases.
What is effective nuclear charge (Zeff)?
The net positive charge experienced by valence electrons.
How does Zeff change across a period?
It increases.
How does atomic size relate to Zeff?
Higher Zeff pulls electrons closer, decreasing size.
How do cations compare in size to their neutral atoms?
Cations are smaller.
How do anions compare in size to their neutral atoms?
Anions are larger.
Why are cations smaller than their neutral atoms?
Loss of electrons increases Zeff and pulls electrons closer.
Why are anions larger than their neutral atoms?
Extra electrons increase repulsion and reduce Zeff.
Among isoelectronic ions, what determines size?
The greater the positive charge, the smaller the ion.
What is ionization energy?
The energy required to remove an electron from an atom in the gas phase.
How does ionization energy change across a period?
It increases.
How does ionization energy change down a group?
It decreases.
Why does ionization energy increase across a period?
Zeff increases, holding electrons more tightly.
