The ancient Greeks knew that all substances consist of particles. Around 420 BC e. The philosopher Democritus proposed that matter consists of tiny, indivisible particles called atoms. All substances are made up of atoms and molecules. Both the atom and the molecule were initially considered indivisible, and only later was it proven that this was not the case. How does an atom differ from a molecule?

Atoms- These are the smallest particles that make up a substance.
Molecules– these are also the elementary particles that make up any substance.

Comparison of atom and molecule

What is the difference between an atom and a molecule?
An atom is an elementary particle of matter. It has its own mass and size and is responsible for the properties of this substance as a chemical element. An atom consists of a nucleus and electrons that move in their orbits around the nucleus. It is the structure of the atom that determines the chemical properties of a substance. Atoms do not occur in a free state. They bind together and form molecules due to the electrical charges of the particles they are made of.
A molecule is what a substance is made of. Molecules can contain two or more atoms that are connected to each other by interatomic bonds. More precisely, we can say that the molecule consists of atomic nuclei and internal electrons that move in their orbits, as well as external valence electrons. Different molecules contain different numbers of atoms of a certain type and different quantities. The molecule has a complex architectural structure, where each atom has its own place and its own well-defined neighbors. The properties of a molecule are determined by how many atoms it contains. These properties are influenced by the order and configuration of the connection of atoms. The atomic structure that forms a molecule can be rigid, but not in all cases. Each atom is in continuous motion, it oscillates around its equilibrium position. In this case, a free molecule during its thermal movement has different configurations. The molecule is electrically a neutral particle. It is the smallest particle of matter that has its chemical properties. In the case of monatomic molecules such as noble gases, the properties of the molecule and the atom are the same. Atoms in a molecule are combined chemical bonds. Such a bond can be created by one or more pairs of electrons shared between two atoms. The molecule can exist independently.

How is an atom different from a molecule?

Atoms form a molecule. An atom consists of a nucleus and electrons that move in their orbits around the nucleus.
Molecules are made up of atoms.
An atom has an electric charge, but a molecule is neutral.
Only a molecule can exist independently.

Atom thing (Garg et al 2014); an element is a type of thing.

An atom is a collection of protons, neutrons and electrons. One isolated atom in the neutral state has some protons, the same number of electrons, and some neutrons (about the same number as protons for lighter elements, about 50% more for heavier elements). The number of neutrons or protons in an atom only changes as a result of radioactive processes or very high-energy interactions, such as you get in particle accelerators. And I mean really High Energy: Even if you think about blowing up sticks of dynamite, that's not enough energy to start messing around with protons and neutrons. Chemistry occurs when atoms come together and exchange electrons or give electrons to each other. Chemical reactions happen all the time, and many of them don't require much energy: moving electrons from atom to atom is often very simple.

So, the chemistry of an atom depends on the number of electrons, and the number of electrons in an isolated atom directly depends on the number of protons. Electrons are so easy to add and remove from atoms (just rub a balloon on your hair: static electricity is you transferring electrons between your hair and balloon), so we classify atoms according to the number of protons they have. Neutrons are not so relevant: I will talk about them at the end.

So the element an atom is determined by the number of protons. All hydrogen atoms have one proton, and all atoms with one proton are hydrogen. Two protons are helium, three are lithium, seventeen are chlorine, 79 are gold, etc. A pure sample of an element contains only atoms of this type: for example, a pure sample of iron contains only atoms with 26 protons. On the other hand, water is not an element: a water molecule consists of two hydrogen atoms (one proton each) sharing electrons with an oxygen atom (eight protons).

Now, what does it mean to say that an element "cannot be broken down into a simpler form" and why are atoms not a "simpler form"? Well they're nothing more simple form, because the iron atom - iron: it's the same shape, it's not simpler. Think about it this way. If I give you a piece of pure iron, all you can do is break it into smaller pieces of iron or make it more complex substance, for example, by allowing it to rust. - Rust is formed from iron and oxygen. The smallest possible piece of iron you could make is a single iron atom, but that's still just an incredibly tiny piece of iron. If you wanted to break a piece of iron beyond the individual iron atoms, you would need to use a nuclear reactor or a particle accelerator or something like that, and then finally you could get something that wasn't iron because you would change number of protons in atoms.

Let's compare this to water. If I give you a bucket of pure water, then, like a piece of iron, you can split it into smaller and smaller samples, eventually ending up with a single molecule of water. But you can do something else: if you pass electricity through water, it splits into pure hydrogen and pure oxygen. These are "simpler" substances because each is made up of atoms of only one element, whereas water has atoms of two elements.

What about neutrons? Well, from a chemistry perspective, they don't do much, and atoms with the same number of protons but different numbers of neutrons are much more similar (they have essentially the same chemistry, for example) than atoms that have the same number of neutrons, but different quantity protons. It makes much more sense to classify by the number of protons, since this determines the number of electrons and determines the chemistry.

Suppose you tried to classify atoms according to the number of neutrons. Best of all, most argon atoms (18 protons) have 22 neutrons, but some chlorine atoms (17 protons) and a fair share of potassium atoms (19 protons) also have 22 neutrons. As you probably know, argon, chlorine and potassium are completely different from each other. On the other hand, potassium atoms with 22 neutrons behave almost identically to the most common kind of potassium atoms, which have 21 neutrons.

How are atoms different?

Translated, “atom” means indivisible. It is named so because for a long time it was considered the smallest part of matter. But further development of science showed that this is not so. So, let's figure out what an atom is made of and how the atoms of different elements differ.

Atomic structure

Today, science knows 126 types of chemical elements. The general structure of their atoms is the same. Each has a nucleus of protons and neutrons around which electrons orbit. Electrons are negatively charged particles. When they rotate around the nucleus, they form electron cloud.

Protons are positively charged particles. At rest, an atom contains the same number of protons and electrons, so chemical element has no electrical charge. However, during reactions, it can give electrons to other elements, becoming a positively charged particle, or take them away, becoming a negatively charged particle. Neutrons do not carry any charge, but they affect the mass of the element. A unifying name was invented for protons and neutrons - nucleons.

Atoms of various elements

Atoms of different elements differ from each other in the number of protons in the nucleus. The number of electrons can change, but the number of protons never. How many protons are contained in the nucleus can be found by serial number element in Mendeleev's periodic table. Hydrogen (No. 1) has 1 electron and 1 proton at rest, lithium
(No. 3) - 3 electrons and 3 protons, carbon (No. 6) - 6 electrons and 6 protons.

Since the number of protons in different atoms different, their masses are also different. The mass of an element is mainly formed by protons and neutrons, because the weight of electrons is negligible. But even atoms of the same element can have different weights due to different numbers of neutrons in the nucleus. Atoms in which the number of neutrons differs from the number of protons are called isotopes. For example, in nature there are carbon atoms C12 (6 protons and 6 neutrons), C13 (6 protons and 7 neutrons) and other varieties with a neutron content of 2 to 16.

Translated, “atom” means indivisible. It is named so because for a long time it was considered the smallest part of matter. But further development of science showed that this is not so. So, let's figure out what an atom is made of and how the atoms of different elements differ.

Atomic structure

Today, science knows 126 types of chemical elements. The general structure of their atoms is the same. Each has a nucleus of protons and neutrons around which electrons orbit. Electrons are negatively charged particles. As they rotate around the nucleus, an electron cloud is formed.

Protons are positively charged particles. At rest, an atom contains the same number of protons and electrons, so such a chemical element has no electrical charge. However, during reactions, it can give electrons to other elements, becoming a positively charged particle, or take them away, becoming a negatively charged particle. Neutrons do not carry any charge, but they affect the mass of the element. A unifying name was invented for protons and neutrons - nucleons.

Atoms of various elements

Atoms of different elements differ from each other in the number of protons in the nucleus. The number of electrons can change, but the number of protons never. How many protons are contained in the nucleus can be determined by the element's serial number in the periodic table of Mendeleev. Hydrogen (No. 1) has 1 electron and 1 proton at rest, lithium
(No. 3) - 3 electrons and 3 protons, carbon (No. 6) - 6 electrons and 6 protons.

Since different atoms have different numbers of protons, their masses also differ. The mass of an element is mainly formed by protons and neutrons, because the weight of electrons is negligible. But even atoms of the same element can have different weights due to different numbers of neutrons in the nucleus. Atoms in which the number of neutrons differs from the number of protons are called isotopes. For example, in nature there are carbon atoms C12 (6 protons and 6 neutrons), C13 (6 protons and 7 neutrons) and other varieties with a neutron content of 2 to 16.

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All the matter around us that we see is made up of various atoms. Atoms differ from each other in structure, size and mass. There are more than 100 types of different atoms, more than 20 types of atoms were obtained by man and are not found in nature, since they are unstable and decay into simpler atoms.

However, even atoms belonging to the same type can differ slightly from each other. Therefore, there is such a thing as a chemical element - these are atoms of the same type. They all have the same nuclear charge, that is, the same number of protons.

Each chemical element has a name and designation in the form of one or two letters from the Latin name of this element. For example, the chemical element hydrogen is designated by the letter H (from the Latin name Hydrogenium), chlorine - Cl (from Chlorum), carbon - C (from Carboneum), gold - Au (from Aurum), copper - Cu (from Cuprum), oxygen - O (from Oxigeium).

The existing chemical elements are listed in the Periodic Table. It is often spoken of as a system ( periodic table), because there are certain strict rules by which this or that element is placed in its table cell. Regular changes in the properties of elements are observed in the rows and columns of the periodic table. Thus, each element in the table has its own number.

Atoms of chemical elements do not change as a result of chemical reactions. The set of substances formed by atoms changes, but not the atoms themselves. For example, if as a result chemical reaction carbonic acid(H 2 CO 3) decomposed into water (H 2 O) and carbon dioxide (CO 2), then no new atoms were formed. Only the connections between them have changed.

Thus, an atom can be defined as the smallest chemically indivisible particle of a substance.

The most abundant element in the universe is hydrogen, followed by helium. These are the simplest chemical elements in structure. The remaining chemical elements account for about 0.1% of all atoms. However, the atoms of other chemical elements have large mass than hydrogen and helium atoms. Therefore, if we express the content of other chemical elements in the Universe in mass percentages, then they will account for 2% of the mass of the total matter of the Universe.

On Earth, the abundance of chemical elements differs greatly when considering the entire Universe. Oxygen (O) and silicon (Si) predominate on Earth. They account for about 75% of the Earth's mass. Next in descending order are aluminum (Al), iron (Fe), calcium (Ca), sodium (Na), potassium (K), magnesium (Mg), hydrogen (H) and many other elements.