Quick Write Draw a picture of a circle and label it’s radius. If the radius of a circle is increased, does it get bigger or smaller? Draw a picture of an atom and label it’s radius. What is atomic radius? Atomic radius is… the size of an atom. Electron Cloud • Electrons (−) Nucleus • Protons (+) • Neutrons (0) 0 0 0 0 What is trend in atomic radius? 1. Atomic radius decreases across a period (LàR) Atomic radius increases down a group (Top à Bottom) Decreases Increases biggest Chihuahua Story I am a dog walker Everyday I walk 8 Chihuahuas The stronger I am, the closer I can pull them towards me Chihuahua Story I am a dog walker Instead of 8 Chihuahuas, I now have 9 I can’t fit any more around me, need a longer leash Quick Write How does this story relate to the trend in atomic radius across a period (L à R)? More protons à more attraction à smaller size How does this story relate to the trend in atomic radius down a group (top à bottom)? More electrons à more rings à bigger size called “shielding” Example #1 Which has a smaller atomic radius, fluorine (F) or nitrogen (N)? biggest Example #2 Which atom is larger in size, sulfur (S) or oxygen (O)? biggest Example #3 What are 3 elements that have atoms smaller than Chlorine (Cl)? biggest Which has a larger atomic radius, Si or P? Which has a larger atomic radius, Si or P? Answer: Si Which has a smaller radius, Cl or F? Which has a smaller radius, Cl or F? Answer: F What is bigger an atom of Cs or Ba? What is bigger an atom of Cs or Ba? Answer: Cs Which of the following is the largest in size? a. Al b. Mg c. S d.Rb Which of the following is the largest in size? a. Al b. Mg c. S Answer: d. Rb d.Rb Which of the following has the smallest atomic radius? a. Rb b. Sr c. Cs Answer: b. Sr d.Ba Rank the following in order of decreasing atomic radius: Cl, K, Mg, Si Rank the following in order of decreasing atomic radius: Cl, K, Mg, Si Answer: K > Mg > Si > Cl Exit Slip 3. In general, how does atomic radius vary throughout the periodic table? a. it decreases across a period from left to right, and decreases down a group from top to bottom b. it increases across a period from left to right, and increases down a group from top to bottom c. it increases across a period from left to right, and decreases down a group from top to bottom d. It decreases across a period from left to right, and increases down a group from top to bottom Exit Slip 3. In general, how does atomic radius vary throughout the periodic table? a. it decreases across a period from left to right, and decreases down a group from top to bottom b. it increases across a period from left to right, and increases down a group from top to bottom c. it increases across a period from left to right, and decreases down a group from top to bottom d. It decreases across a period from left to right, and increases down a group from top to bottom Answer: d..