~ 5.2 - chem ~
~ Periods ~
Periods = horizontal rows (1-7)
Period number → how many electron shells an atom has
Examples: Sodium is in period 3; contains 3 electron shells
~ Groups ~
Groups = vertical columns (1-18)
Group number (main groups; 1,2,12-18) tells number of valance electrons
Valance electrons = electrons in the outer shell
Example: Sodium is in group 1; it was 1 valance electron
~ Special Blocks ~
Transition elements (groups 3-13)
~ 5.2 - chem ~ 1
~ Periods ~
Periods = horizontal rows (1-7)
Period number → how many electron shells an atom has
Examples: Sodium is in period 3; contains 3 electron shells
~ Groups ~
Groups = vertical columns (1-18)
Group number (main groups; 1,2,12-18) tells number of valance electrons
Valance electrons = electrons in the outer shell
Example: Sodium is in group 1; it was 1 valance electron
~ Special Blocks ~
Transition elements (groups 3-13)
~ 5.2 - chem ~ 1
