Which of the following elements has the maximum atomic radius?

Explanation

The correct answer isNa. The decreasing order of atomic radius is Na (227pm) > P (195pm) > S (180pm) > Cl (175pm) . Explanation: When two atoms have the same value of n for the valence electrons, the atom with the greater number of protons will generally have a greater effective nuclear charge to draw the valence electrons closer to the nucleus and, thus, decrease the atomic radius . Since chlorine's 17 protons are greater than sodium's 11 protons ,chlorine will have a greater effective nuclear charge to draw chlorine's valence electrons closer to the nucleus and, thus, chlorine is expected to have a smaller atomic radius. While sodium with the lower effective nuclear charge is expected to have a larger atomic radius . Important Points In the periodic table, the atomic radius of elements tends to decrease as you move across a row from left to right. Ionic radii increase down a group as more shells are added. ELEMENT ATOMIC NUMBER GROUP / PERIOD Na (Sodium) 11 1 / 3 P (Phosphorus) 15 15 / 3 S (Sulphur) 16 16 / 3 Cl (Chlorine) 17 17 / 3 Key Points Sodium is highly reactive so that it is stored in oil or kerosene because it spontaneously ignites in water. At room temperature, sodium metal is soft enough that you can cut it with a butter knife. White phosphorus is used in flares and incendiary devices. Red phosphorus is in the material stuck on the side of matchboxes, used to strike against safety matches to light them.