Chemistry – Atomic Radius Activity
Name ______________________________
Date ________________ Pd ___________
Purpose:
The purpose of this lab is to mathematically determine the radius of a metal ion.
Procedure #1: Determine the number of atoms in a given piece of metal.
1. Obtain a piece of metal from the teacher and find the mass of the metal.
2. Convert the mass of the metal to moles. Then, using Avagadro’s number of atoms in a mole, determine the number of atoms
in your sample of metal.
Metal:
_____________________
1) Mass of the metal:
_______________
3) Number of atoms in the metal:
________________
2) Moles of metal:
________________
Procedure #2: Determine the volume of the metal.
1. Using your textbook or the lab technique used earlier in this course, find the density of your metal.
2. From the density and the mass of the metal, find the volume of the metal.
Density of the metal:
_____________________
Volume of the metal:
_____________________
Procedure #3: Determine the volume and radius of a single atom.
1. Divide the volume of your metal by the number of atoms in the metal. This calculation is the volume of a single atom.
2. Using the equation for the volume of a sphere, V =
, calculate the radius of a single atom.
Volume of a single atom:
_______________
Radius of a single metal atom:
Refer to the textbook to find the expected atomic radius:
Calculate the % error of atomic radius.
_______________________
_________________
_______________________
Questions:
1) Refer to the diagram below to help explain why there is error associated with this method of determining the size of an
atom.
2) Use the table of atomic & Ionic radii below to explain the periodic trend of atomic radius. Use the correct terminology
to explain your answer (period, group, atomic number, atomic radii).
Ionic radii
The size of atoms is difficult to define, let alone measure. The size is determined by maximum charge density, which itself is a
function of the type and number of nearest neighbor atoms. Therefore it is possible to assign each ion a radius such that the sum of the
radii of two adjacent ions is each to the interatomic (separation) distance. Thus we can determine effective radii by measuring bond
lengths in crystals. (see the image below)
Paraphrase this statement to explain how the sizes of atoms are measured.
3) Use the table of atomic & Ionic radii below to explain the periodic trend of ionic radius. Use the correct terminology to
explain your answer (period, group, atomic number, ionic radii).