In 1913, Niels Bohr developed his famous atomic model. In this model, electrons rotate in circular orbits around the nucleus, occupying the lowest possible energy orbit, or the closest possible orbit to the nucleus.

However, the popular idea of an atom is, to a certain extent, a schematic distortion, a model of understanding for laymen... an approach that bears little or no resemblance to reality. Atoms are not as they are drawn in textbooks. In fact, atoms are far from all the same: They differ greatly from each other.

Densities and shapes

As explained Santiago Alvarez in the book Of women, men and molecules, the density of atoms can vary by two orders of magnitude from one element to another, more than the density of the Earth varies from the crust to the core:

If we calculate the densities of the electron cloud and the nucleus separately, in the case of helium we find values of 2×3 10¹⁷ and 3.52 x 10^-5 kg/m³, respectively. That is, the density of the nucleus is about 10^twenty-one times greater than that of its surrounding electrons. We do not have references in the everyday world to gauge the meaning of these densities. Not even the air in the stratosphere has a density as small as that of the electron cloud. We would have to go up to the thermosphere, about 100 km above the Earth's surface, to find a comparable density. In the case of the core, only a neutron star has such a high density, surpassed only by that of black holes.

Nor are atoms always spherical.. And even less is an atom within a molecule spherical. Even atoms of the same element can differ in a series of attributes:

• Number of neutrons (in different isotopes).
• Number of electrons (in multiple oxidation states).
• Degree of pairing of electrons (in various spin states).
• Variable molecular environment in coordination number and stereochemistry that also affects shape and size.

Thus, we could affirm that the invariant property between the atoms of the same element is its atomic number (number of protons in its nucleus), the property that defines a chemical element, despite the fact that the chemical reactivity and its ability to Bond formation resides in the valence electrons.

In this way, the writing of Margaret Lucas Cavendish, Duchess of Newcastle, in her book Poems and Fancies (1653):

• Pointed atoms make the Fire subtle, fast and dry,
• The Long ones fly like arrows in the air,
• The Round ones become water, moist,
• The Squares on Earth, with immovable Form;
• Square atoms make up hard Minerals,
• Soft vegetables appropriate round atoms.

However, we need models to understand reality, because reality is not understandable in its entirety:

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The news

The density of different atoms can vary more than the density of the Earth's crust and nucleus

was originally published in

Xataka Science

by
Sergio Parra

.

According to a new study, the mass of all our things (buildings, roads, cars, etc.) now exceeds the mass of all living things on the planet.

It is not surprising that this is the case if we take into account that the amount of new material added each week It is equal to the total mass of the almost 8 billion people on Earth (Humans constitute approximately 0.01% of the planet's biomass).

Prepared dough: exponential growth

In 1900, the mass of human materials was only 3% of the Earth's total biomass. Since then, materials have doubled approximately every 20 years..

The glut of concrete and asphalt began during the boom years between World War II and the 1973 oil crisis, when developed countries began building.

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Meanwhile, total biomass has gradually decreased since 1900 due to deforestation and other reasons. The increase in human mass is driven by the use of geological resources: rocks, minerals and metals.

Human-created mass finally surpassed Earth's total living biomass this year. The timing of that transition depends on whether the biomass accounts for the water. If water is included, biomass will remain larger than human materials until about 2037.

Even so, the comparisons are very striking: Buildings and other infrastructure weigh more than the world's trees and bushes. And the mass of plastic is twice that of all animals.

The world can be divided into three kinds of matter depending on its purpose: dead matter, living matter and processed matter. Let's analyze how many billion tons there are of each type of matter in the world... and discover that There is more matter made from cows than from humans!:

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The news

Each week, the mass of all our material objects added to the world is equal to the mass of all the world's inhabitants.

was originally published in

Xataka Science

by
Sergio Parra

.