How many protons an atom has.
What is atomic number?
A trend that increases down a group.
What is shielding, atomic radius, or effective nuclear charge?
The first three elements of the halogen group.
What are fluorine, chlorine, and bromine?
Conductive, shiny, malleable, and ductile. Found on the left side of the periodic table.
What are metals?
This is the current organization of the periodic table.
What is increasing atomic number?
They organized the first periodic table by increasing atomic mass.
Who is Dmitri Mendeleev?
The alkaline Earth metal with the highest ionization energy.
What is beryllium?
The group where the first element is oxygen.
What is the oxygen group or group 6?
They are found along the zigzag line starting at (but not including) aluminum.
What are the metalloids?

The bottom number in this box.
What is the average atomic mass?
The vertical columns on the periodic table.
What are groups or families?
Valence electron distance from the nucleus and shielding causes this to increase across a period and decrease down a group.
What is ionization energy?
This group contains the elements lithium, potassium, and sodium.
What are the alkali metals?
These elements are located below the main section of the periodic table.
What are the inner transition metals or rare earth metals?
The amount of valence electrons in iodine (I).
What is 7?
The horizontal rows on the periodic table.
What are periods?
This element has the highest electronegativity value on the periodic table.
What is fluorine?
Similar properties down a group allowed Mendeleev to predict the existence of these.
What were undiscovered elements?
These are classified as metals and found in the d-block of the periodic table.
What are the transition metals?
This element has the smallest atomic radius in 4th period.
What is krypton?
The negatively charged subatomic particles that occupy the outermost energy level.
What are valence electrons?
This stays the same across a period and helps describe why atomic radii decreases and effective nuclear charge increases across a period.
What is shielding?
This element is a noble gas that does not have eight valence electrons.
What is helium?
All nonmetal elements are located in this block of the periodic table.
What is the p-block?
He came up with the current organization of the periodic table.
Who is Henry Mosely?