Periodic table structure

Question 1

define period

Answer 1

all elements in a period have the same number of electron shells

Question 2

define group

Answer 2

all elements down a group have the same number of outer electrons

Question 3

describe the structure of the periodic table

Answer 3

the arrangement of elements:
* by increasing atomic (proton) number
* in periods showing repeating trends in physical and chemical properties (periodicity)
* in groups having similar chemical properties