atomic number - correct answer ✔✔number of protons and number of electrons in an uncharged atom
average atomic mass - correct answer ✔✔weighted average if all known isotopes
how are elements arranged - correct answer ✔✔in order of increasing atomic number
what are periods - correct answer ✔✔there are 7 periods, and they are horizontal, where elements are
arranged
what are groups - correct answer ✔✔Vertical columns on the periodic table
who discovered periodicity - correct answer ✔✔mendeleev
what was the trend mendeleev used when discovering periodicity - correct answer ✔✔predict
properties of undiscovered elements, in 1869
what are trends - correct answer ✔✔chemical and physical properties of the elements follow both
periodic and group trends
what is electron configuration - correct answer ✔✔the electron configuration of the outer energy levels
aka valence levels, determines the chemical properties of the elements
what is the number of the period in which an element is found is the same as the number of the energy
levels - correct answer ✔✔valence electrons
what do elements in a period have the same number of - correct answer ✔✔electron shells