How far away might one of its electrons be?
To make things a little weirder, the electron cloud isn’t an actual cloud, in which electrons can be nailed down to a physical point in space. Rather, it’s an area of probability, in which the size of the atom is defined by the probability that an electron will be found at a certain distance from its nucleus.
A hydrogen atom is about 99.9999999999996% empty space. Put another way, if a hydrogen atom were the size of the earth, the proton at its center would be about 200 meters (600 feet) across.
Atomic radii vary in a predictable way across the periodic table. As can be seen in the figures below, the atomic radius increases from top to bottom in a group, and decreases from left to right across a period. Thus, helium is the smallest element, and francium is the largest.
The nucleus is the atom’s central core and contains more than 99.9 percent of its mass. ‘ And if the nucleus was expanded to the size of a marble, the outer edge of the atom would be nearly a football field away. A quick primer on the atom: Atoms are composed of protons, neutrons and electrons.
In ordered solids, the atomic spacing between two bonded atoms is generally around a few ångströms (Å), which is on the order of 10−10 meters. However, in very low density gases (for example, in outer space) the average distance between atoms can be as large as a meter.
The Bohr radius (a0) is a physical constant, approximately equal to the most probable distance between the nucleus and the electron in a hydrogen atom in its ground state. It is named after Niels Bohr, due to its role in the Bohr model of an atom. Its value is 5.29177210903(80)×10−11 m.
The nucleus only contains protons and neutrons. It does not contain electrons. Electrons surround the nucleus and are present in the atomic orbitals.
Principle: Electron pairs around a central atom arrange themselves so that they can be as far apart as possible from each other. The repulsion between negatively charged electron pairs in bonds or as lone pairs causes them to spread apart as much as possible.
What size would the atom be in a model where the Earth represented the nucleus? The diameter of the Earth is 1.3 × 10 7 m. Therefore the atom is 5 × 10 4 larger than the nucleus. The model of the atom must be 5 × 10 4 times larger than this.
Electrons, which are almost 2,000 times smaller than protons and neutrons, are found whizzing about outside the nucleus in regions that scientists call shells or orbitals. If the nucleus were the size of a golf ball then the nearest electron would be about a mile away. The space in between is mostly empty space!
The Bohr radius, is the estimated distance between protons in the nucleus and electrons – but electrons aren’t solid, stationary particles… The simple answer would be about one-twentieth of a nanometre.
Electrons are indeed far away from the nucleus! If we could magnify the simplest hydrogen atom so that its nucleus (a proton) were the size of a basketball, then its lone electron would be found about 2 miles away. All of the space in between the electron and the basketball-size nucleus is empty!