9 The atomic radius of magnesium is 150 pm. The atomic radius of strontium is 200 pm. What
is the atomic radius of calcium? (Atomic radii have been measured for most elements. They
are commonly reported in units of picometers 1 pm = 10-12 m)

180 pm

Explanation:

Atomic radius can be defined as a measure of the size (distance) of the atom of a chemical element such as hydrogen, oxygen, carbon, nitrogen etc, typically from the nucleus to the valence electrons. The atomic radius of a chemical element decreases across the periodic table, typically from alkali metals (group one elements such as hydrogen, lithium and sodium) to noble gases (group eight elements such as argon, helium and neon) i.e from the left to the right. Also, the atomic radius of a chemical element increases down each group of the periodic table, typically from top to bottom (column).

Hence, the atomic radius of magnesium, strontium and calcium is 150 pm, 200 pm and 180 pm respectively.

Additionally, the unit of measurement of the atomic radius of chemical elements is picometers (1 pm = 10 - 12 m).