Chem-To-Go Lesson 11 Unit 3 ATOMIC RADIUS & IONIC RADIUS
Chem-To-Go Lesson 11Unit 3
ATOMIC RADIUS & IONIC RADIUS
TRENDS
Trend = a repeating pattern
Periodic Trend = a repeating pattern on the periodic table
ATOMIC RADIUS
Definition: ½ the distance between the nuclei of two identical touching atoms
ATOMIC RADIUSPeriod trend: [row pattern]; atomic radius DECREASES from left to right across a row Group trend: [column pattern]; atomic radius DECREASES from bottom to top of a column
WHY?•Radius decreases across a period because the nucleus is gaining more protons to become larger and more strongly positive. The electron cloud is drawn in by forces of attraction.
• Radius decreases up a group because there are fewer energy levels at the top of the periodic table.
PERIOD TREND
GR
OU
P T
REN
D
ATOMIC RADIUSMemory
Tool
SAMPLE MULTIPLE CHOICE:
1. Which of the following atoms will has the smallest radius?
a. Tin b. Strontium c. Selenium d. Arsenic
• Use a periodic table!• Find all of the elements.• Apply the trend.
ATOMIC RADIUSMemory
Tool
SAMPLE MULTIPLE CHOICE:
2. Which of the following atoms will has a larger radius than calcium?
a.Aluminum b. Copper c. Potassium d. None
• Use a periodic table!• Find all of the elements.• Apply the trend.
IONIC RADIUS
Definition: size of the ion; usually compared to the size of its neutral atom
CATION RADIUS
ANION RADIUS
IONIC RADIUS
Cations form by losing electrons. As electrons are
lost, the ion becomes smaller.
Anions form by gaining electrons. As electrons are
gained, the ion becomes larger.