Answer is: <span>an atomic radius.
</span>The atomic radius<span> of a </span>chemical element<span> is a measure of the size of its atom.
</span>The atomic radius varies with increasing atomic number, but usually increases because of increasing of number of electrons.
The atomic radius decreases across the periods because an increasing number of protons, because <span>greater attraction between the protons and electrons.</span>
Group 8 nonmetals; <span>He, Ne, Ar, Kr, Xe, and Rn</span>
An example of an allotrope is carbon:
Carbon can exist in graphite, diamond and amorphous
B- Carbon nitrogen and oxygen. All organisms are made up of carbon, oxygen is essential to breath, and nitrogen makes up most of earth's atmosphere.
Answer:
Sodium Carbonate was the unknown powder
