What is an atom in physics? simple definition

According to chemists, atoms are the building blocks of matter. This hypothesis, which is now proven, was born several centuries ago.

Ancient thinkers believed that atoms were indivisible. Moreover, the word atom comes from the ancient Greek ἄτομος [átomos] Which means Unbreakable. This idea appeared in particular among pre-Socratic ancient Greece, in the fifth century BC. As for the written records that you deal withThe presence of these small items (molecules or atoms), dating back several centuries later. between the seventeenth and nineteenth centuryFrom great authors Mention of these entities in their writings. Descartes, authorthe scientist, Galileo Il Saggiatore, Part of it. However, it is onlyIn 1908 that John Perrin He succeeded in proving it Matter is made of atoms.

What is corn?

Atom is the name physicists use for the name The smallest part of a simple body It can chemically combine with another substance. In simple terms, all solids, liquids or gases are mainly composed of atoms.

What is an atom made of?

If the scholars of the past still believe thatcorn is indivisibletoday, This is no longer the case. It has been proven that an atom make up of protonsAnd the neutrons And the of electrons. Each of these entities is itself a group of smaller elements, called quarks. However, we will focus on corn and its three components.

Protons and neutronsthe group also called nucleonsAnd the make up core from corn. protons being loaded PositivelyWhile neutronsas their name suggests, they have a file neutral load.

Regarding for electronsthat they revolve around the nucleus This is mainly due to its negative charge. Specifically, its negative charge causes it to be attracted to the nucleus (positive charge). Excite these entities around the nucleus form an electronic cloud. Depending on their energy, electrons can have a more or less intense movement.

What is the difference between an atom and another?

An atom has a neutral charge because it contains Equal number of protons and electrons. This number sets Atomic number note zWhile that neutrons symbolizes her Not. The sum of Z and N gives the amount of observed nucleons to me Who is the mass number. This gives the following formula: a = p + n.

chemical elements

All An atom belonging to a chemical element which has its own symbol (X) preceded by its atomic number (_zX). indeed it is The amount of protons (or electrons) in the atom that Determine its chemical element. for example, hydrogen atom It has one proton and is symbolized by . ₁ h. In addition, iron atomhas 26 protons and is represented by the symbol ₂₆Iron.

This classification was for atoms Imagined by Dmitri Mendeleev in 1869. It depends in particular on the mass and chemical properties of the atoms. Over time, this method of classification has evolved into its current form: Periodic Table of the Elements.

isotopes

All atoms are one chemical element You have Same amount of protons. Regarding The number of neutrons, can vary. Then atoms of the same chemical element with different amounts of neutrons are called isotopes.

hydrogenfor example, displays Three natural isotopes: Simple hydrogen, deuterium (one neutron) and tritium (two neutrons). The first isotope, which is also the most common, does not contain any neutrons.

for example, uranium which contains 92 protons Two natural counterparts: Uranium 235 and Uranium 238. Here the numbers 235 and 238 refer to the mass number (A) or the number of nucleons. Like A = Z + N, so 235 = 92 + 143 and 238 = 92 + 146.

To classify the different isotopes, simply write the symbol of the chemical element along with the number of nucleons. Regarding the condition of Uranium-235 And the Uranium-238this gives ²³⁸yo And the²³⁵yo.

Invisible, but very present

In the past, people thought so Atoms did not existbecause they were in Not being able to notice. Because, corn diameter (core and electronic cloud) measurement between 0.5 .10^-10 M (hydrogen) l 4.3 10^-10 M (radium).

In other words, it should be Multiply by 1 million the diameter of a hydrogen atom to get ithair. If the atom is small, then its nucleus is smaller. In fact, Diameter atomic nucleus Around 100,000 times less so from atomic cloud.

Today, these entities can be observed thanks to scanning microscopes.

See also: What is a molecule? simple definition

The volume and mass of the corn

Bloc

neutron And the proton You have approximately equal mass. but, The mass of the electron is 1840 times less for a neutron or a proton. And therefore, majority of mass of an atom contained in the nucleus. It’s the same with Solar Systemwhose Mass is concentrated in the sun.

On the other hand, Calculate the mass The kernel is very simple once we know it mass number. enough to multiply a by nucleus block And it’s almost 1.67.10^-27 kg. Of course, this calculation is just an estimate of the mass of the atom. However, it is possible that Accurate mass determination from him with mass spectrometer.

corn size

An atom has an extremely small volume as its mass. For comparison, a iron pin head includes approx 60 million billion iron atoms. However, the pin tip size is only 1mm³.

Density of the nucleus of an atom

The corn kernel Iron Present Diameter of order 10^-14 M and a mass of about 9.3.10^-26 kg. Using the formula: Density = Mass/Volume, the result is 1.8.10¹⁷ kg/m³. In fact, One cubic centimeter of iron core weighs approx one hundred million tons. wide Pinheadsuch a concentration of iron core will have mass 180 thousand tons.

Dark matter, just about everywhere

What is between the nucleus of an atom and its electron cloud? The answer is “nothing”! Finally, there is what scientists have called “dark matter” and I stayed still unknown. However, researchers believe thatIt makes up about 95% of the entire universe.