The atomic radii of the elements are almost constant, so why does it seem like there is a huge difference between the size of an atom and the size of a molecule?
In chemistry, it is important to understand how atoms interact with each other. This is because molecules are made up of atoms that bond together in specific ways. These bonds are what determine the physical properties of a molecule, such as its melting point or boiling point. So why do some elements have very large atoms while others have much smaller ones?
If you look at the periodic table, you will notice that some elements have very large atomic radii while others have much smaller ones. For example, hydrogen has an atomic radius of 0.081 nanometers (nm), while fluorine has an atomic radius of 0.118 nm.
So what determines the size of an atom? The answer lies in its number of protons and electrons.
What determines the size of an atom?
All atoms contain protons and electrons that balance each other out to form neutral particles. Atoms with more protons than electrons will be positively charged and those with more electrons than protons will be negatively charged.
The number of protons in an atom defines which element it is and how many electrons it has.
“So what determines the size?”
In order for two atoms to bond together, they must share their valence electrons equally. This means that if one atom has two valence electrons then another must also have two valence electrons so they can form a bond.