atomic+radius

__Atomic radius__ is measured from the center of an atom's nucleus to its outermost electron energy level.

The radius of an atom is extremely small, on the order of tens or hundreds of trillionths of a meter. These measurements are reported in angstroms (1 angstrom ( Å) = 0.0000000001 meter) or picometers (1 picometer (//pm//) = 0.000000000001 meter).

A good analogy for an atom having an atomic radius of 100 pm is to say that if a typical marble is the size of its atomic nucleus, then its outermost electrons are on average 1000 meters away!

To give you #|an idea as to how small these atoms are, consider a copper atom, which has an atomic radius of 135 pm. A penny is coated in copper, so imagine if you lined up the copper atoms across the face of a penny. That would require 74 million copper atoms!


 * Atomic Radius Trend**

Atomic radius is influenced by one property - electronegativity. As the pull on electrons gets stronger, their orbitals get smaller, and the atoms are thus smaller in size.

Within a vertical group, atoms get larger going down. There are more layers of electrons, which are further from the nucleus.

Within a horizontal period, the atoms get smaller from left to right because the number of protons in the nucleus increases.



Here is a video explaining atomic radius trends.

This chart shows some radius values in angstroms.