Sn is a chemical element as it is read. Names of chemical elements

2.1. Chemical language and its parts

Mankind uses many different languages. Except natural languages(Japanese, English, Russian - more than 2.5 thousand in total), there are also artificial languages e.g. Esperanto. Among the artificial languages ​​are languages various Sciences. So, in chemistry, one uses its own, chemical language.
chemical language- a system of symbols and concepts designed for concise, concise and visual recording and transmission of chemical information.
A message written in most natural languages ​​is divided into sentences, sentences into words, and words into letters. If we call sentences, words and letters parts of the language, then we can distinguish similar parts in the chemical language (Table 2).

Table 2.Parts of the chemical language

It is impossible to master any language at once, this also applies to the chemical language. Therefore, for now, you will only get acquainted with the basics of this language: learn some "letters", learn to understand the meaning of "words" and "sentences". At the end of this chapter, you will be introduced to titles chemicals are an integral part of the chemical language. As you study chemistry, your knowledge of the chemical language will expand and deepen.

CHEMICAL LANGUAGE.
1. What artificial languages ​​do you know (except those named in the text of the textbook)?
2. How do natural languages ​​differ from artificial ones?
3. Do you think it is possible to do without the use of chemical language when describing chemical phenomena? If not, why not? If so, what would be the advantages and disadvantages of such a description?

2.2. Symbols of chemical elements

The symbol for a chemical element denotes the element itself or one atom of that element.
Each such symbol is an abbreviated Latin name of a chemical element, consisting of one or two letters of the Latin alphabet (see Appendix 1 for the Latin alphabet). The symbol is capitalized. Symbols, as well as Russian and Latin names of some elements, are given in Table 3. Information about the origin of Latin names is also given there. There is no general rule for the pronunciation of symbols, therefore Table 3 also shows the "reading" of a symbol, that is, how this symbol is read in a chemical formula.

It is impossible to replace the name of an element with a symbol in oral speech, and in handwritten or printed texts this is allowed, but not recommended. Currently, 110 chemical elements are known, 109 of them have names and symbols approved by the International Union of Theoretical and Applied Chemistry (IUPAC).
Table 3 provides information on only 33 elements. These are the elements that you will encounter first when studying chemistry. Russian names (in alphabetical order) and symbols of all elements are given in Appendix 2.

Table 3Names and symbols of some chemical elements

Name
	latin		Writing
-	Writing	Origin	-	-
Nitrogen	N itrogenium	From Greek. "giving birth to saltpeter"		"en"
Aluminum	Al uminium	From lat. "alum"		"aluminum"
Argon	Ar gon	From Greek. "inactive"		"argon"
Barium	Ba rium	From Greek. " heavy"		"barium"
Bor	B orum	From Arabic. "white mineral"		"bor"
Bromine	Br omum	From Greek. "malodorous"		"bromine"
Hydrogen	H hydrogenium	From Greek. "giving birth to water"		"ash"
Helium	He lium	From Greek. " The sun"		"helium"
Iron	Fe rrum	From lat. "sword"		"ferrum"
Gold	Au rum	From lat. "burning"		"aurum"
Iodine	I odum	From Greek. " Violet"		" iodine"
Potassium	K alium	From Arabic. "lye"		"potassium"
Calcium	Ca lcium	From lat. "limestone"		"calcium"
Oxygen	O xygenium	From Greek. "producer of acids"		" about"
Silicon	Si licium	From lat. "flint"		"silicium"
Krypton	kr ypton	From Greek. "hidden"		"krypton"
Magnesium	M a g nesium	From the name peninsulas of Magnesia		"magnesium"
Manganese	M a n ganum	From Greek. "purifying"		"manganese"
Copper	Cu prum	From Greek. name about. Cyprus		"cuprum"
Sodium	Na trium	From Arabic, "detergent"		"sodium"
Neon	Ne on	From Greek. " new"		"neon"
Nickel	Ni colum	From him. "copper of St. Nicholas"		"nickel"
Mercury	H ydrar g yrum	Lat. "liquid silver"		"hydrargyrum"
Lead	P lum b um	From lat. the name of the alloy of lead and tin.		"plumbum"
Sulfur	S sulfur	From Sanskrit "flammable powder"		"es"
Silver	A r g entum	From Greek. " light"		"argentum"
Carbon	C arboneum	From lat. " coal"		"ce"
Phosphorus	P hosphorus	From Greek. "bringer of light"		"pe"
Fluorine	F luorum	From lat. verb "to flow"		"fluorine"
Chlorine	Cl orum	From Greek. "greenish"		"chlorine"
Chromium	C h r omium	From Greek. " dye"		"chrome"
Cesium	C ae s ium	From lat. "sky blue"		"cesium"
Zinc	Z i n cum	From him. "tin"		"zinc"

2.3. Chemical formulas

Used to refer to chemicals chemical formulas.

For molecular substances, the chemical formula can also denote one molecule of this substance.
Information about a substance can be different, so there are different types of chemical formulas.
Depending on the completeness of information, chemical formulas are divided into four main types: protozoa, molecular, structural and spatial.

Subscripts in the simplest formula do not have a common divisor.
Index "1" is not put in formulas.
Examples of the simplest formulas: water - H 2 O, oxygen - O, sulfur - S, phosphorus oxide - P 2 O 5, butane - C 2 H 5, phosphoric acid - H 3 PO 4, sodium chloride (table salt) - NaCl.
The simplest formula of water (H 2 O) shows that the water contains the element hydrogen(H) and element oxygen(O), and in any portion (a portion is a part of something that can be divided without losing its properties.) of water, the number of hydrogen atoms is twice the number of oxygen atoms.
Number of particles, including number of atoms, denoted by the Latin letter N. Denoting the number of hydrogen atoms - N H , and the number of oxygen atoms is N O , we can write that

Or N H: N O=2:1.

The simplest formula of phosphoric acid (H 3 PO 4) shows that phosphoric acid contains atoms hydrogen, atoms phosphorus and atoms oxygen, and the ratio of the numbers of atoms of these elements in any portion of phosphoric acid is 3:1:4, that is

NH: N P: N O=3:1:4.

The simplest formula can be drawn up for any individual chemical substance, and for a molecular substance, in addition, molecular formula.

Examples of molecular formulas: water - H 2 O, oxygen - O 2, sulfur - S 8, phosphorus oxide - P 4 O 10, butane - C 4 H 10, phosphoric acid - H 3 PO 4.

Nonmolecular substances do not have molecular formulas.

The sequence of writing the symbols of elements in the simplest and molecular formulas is determined by the rules of the chemical language, which you will learn as you study chemistry. The sequence of characters does not affect the information conveyed by these formulas.

Of the signs reflecting the structure of substances, we will use so far only valence stroke("dash"). This sign shows the presence between the atoms of the so-called covalent bond(what kind of connection is this and what are its features, you will soon find out).

In the water molecule, the oxygen atom is connected by simple (single) bonds with two hydrogen atoms, and the hydrogen atoms are not connected to each other. This is clearly shown by the structural formula of water.

Another example: the sulfur molecule S 8 . In this molecule, 8 sulfur atoms form an eight-membered cycle in which each sulfur atom is connected to two other atoms by simple bonds. Compare the structural formula of sulfur with the three-dimensional model of its molecule shown in fig. 3. Please note that the structural formula of sulfur does not convey the shape of its molecule, but only shows the sequence of connecting atoms by covalent bonds.

The structural formula of phosphoric acid shows that in the molecule of this substance one of the four oxygen atoms is connected only to the phosphorus atom by a double bond, and the phosphorus atom, in turn, is connected to three more oxygen atoms by simple bonds. Each of these three oxygen atoms, in addition, is connected by a simple bond with one of the three hydrogen atoms present in the molecule./p>

Compare the following three-dimensional model of the methane molecule with its spatial, structural and molecular formula:

In the spatial formula of methane, wedge-shaped valence strokes, as if in perspective, show which of the hydrogen atoms is "closer to us" and which is "farther from us".

Sometimes the spatial formula indicates the bond lengths and the values ​​of the angles between the bonds in the molecule, as shown in the example of the water molecule.

Nonmolecular substances do not contain molecules. For the convenience of carrying out chemical calculations in a nonmolecular substance, the so-called formula unit.

Examples of the composition of the formula units of some substances: 1) silicon dioxide (quartz sand, quartz) SiO 2 - the formula unit consists of one silicon atom and two oxygen atoms; 2) sodium chloride (common salt) NaCl - the formula unit consists of one sodium atom and one chlorine atom; 3) iron Fe - a formula unit consists of one iron atom. Like a molecule, a formula unit is the smallest portion of a substance that retains its chemical properties.

Table 4

Information Conveyed by Different Types of Formulas

Formula type	The information passed by the formula.
Protozoa Molecular Structural Spatial		Atoms of which elements make up a substance. The ratios between the numbers of atoms of these elements. The number of atoms of each of the elements in the molecule. Types of chemical bonds. The sequence of connecting atoms by covalent bonds. Multiplicity of covalent bonds. Mutual arrangement of atoms in space. Bond lengths and bond angles (if specified).

Let us now consider, with examples, what information formulas of different types give us.

1. Substance: acetic acid. The simplest formula is CH 2 O, the molecular formula is C 2 H 4 O 2, the structural formula

The simplest formula tells us that
1) acetic acid contains carbon, hydrogen and oxygen;
2) in this substance, the number of carbon atoms is related to the number of hydrogen atoms and to the number of oxygen atoms, as 1:2:1, that is N H: N C: N O = 1:2:1.
Molecular formula adds that
3) in a molecule of acetic acid - 2 carbon atoms, 4 hydrogen atoms and 2 oxygen atoms.
Structural formula adds that
4, 5) in the molecule, two carbon atoms are linked by a single bond; one of them, in addition, is associated with three hydrogen atoms, with each single bond, and the other with two oxygen atoms, with one double bond, and with the other a single bond; the last oxygen atom is also linked by a simple bond to the fourth hydrogen atom.

2. Substance: sodium chloride. The simplest formula is NaCl.
1) Sodium chloride contains sodium and chlorine.
2) In this substance, the number of sodium atoms is equal to the number of chlorine atoms.

3. Substance: iron. The simplest formula is Fe.
1) The composition of this substance includes only iron, that is, it is a simple substance.

4. Substance: trimetaphosphoric acid . The simplest formula is HPO 3, the molecular formula is H 3 P 3 O 9, the structural formula

1) The composition of trimetaphosphoric acid includes hydrogen, phosphorus and oxygen.
2) N H: N P: N O = 1:1:3.
3) A molecule consists of three hydrogen atoms, three phosphorus atoms and nine oxygen atoms.
4, 5) Three phosphorus atoms and three oxygen atoms, alternating, form a six-membered cycle. All links in the cycle are simple. Each phosphorus atom, in addition, is associated with two more oxygen atoms, with one - a double bond, and the other - a simple one. Each of the three oxygen atoms linked by simple bonds to phosphorus atoms is also linked by a simple bond to a hydrogen atom.

Phosphoric acid - H 3 PO 4(another name is phosphoric acid) is a transparent colorless crystalline substance of a molecular structure, melting at 42 o C. This substance is very soluble in water and even absorbs water vapor from the air (hygroscopically). Phosphoric acid is produced in large quantities and is used primarily in the production of phosphate fertilizers, as well as in the chemical industry, in the production of matches, and even in construction. In addition, phosphoric acid is used in the manufacture of cement in dental technology, is part of many medicines. This acid is cheap enough that in some countries, such as the United States, very pure phosphoric acid, highly diluted with water, is added to refreshments to replace expensive citric acid.

Methane - CH 4. If you have a gas stove at home, then you come across this substance every day: the natural gas that burns in the burners of your stove is 95% methane. Methane is a colorless and odorless gas with a boiling point of -161 o C. When mixed with air, it is explosive, which explains the explosions and fires that sometimes occur in coal mines (another name for methane is firedamp). The third name of methane - swamp gas - is due to the fact that bubbles of this particular gas rise from the bottom of swamps, where it is formed as a result of the activity of certain bacteria. In industry, methane is used as a fuel and raw material for the production of other substances. Methane is the simplest hydrocarbon. This class of substances also includes ethane (C 2 H 6), propane (C 3 H 8), ethylene (C 2 H 4), acetylene (C 2 H 2) and many other substances.

Table 5.Examples of formulas of different types for some substances-

How to use the periodic table? For an uninitiated person, reading the periodic table is the same as looking at the ancient runes of elves for a dwarf. And the periodic table can tell a lot about the world.

In addition to serving you in the exam, it is also simply indispensable for solving a huge number of chemical and physical problems. But how to read it? Fortunately, today everyone can learn this art. In this article we will tell you how to understand the periodic table.

The periodic system of chemical elements (Mendeleev's table) is a classification of chemical elements that establishes the dependence of various properties of elements on the charge of the atomic nucleus.

History of the creation of the Table

Dmitri Ivanovich Mendeleev was not a simple chemist, if someone thinks so. He was a chemist, physicist, geologist, metrologist, ecologist, economist, oilman, aeronaut, instrument maker and teacher. During his life, the scientist managed to conduct a lot of fundamental research in various fields of knowledge. For example, it is widely believed that it was Mendeleev who calculated the ideal strength of vodka - 40 degrees.

We do not know how Mendeleev treated vodka, but it is known for sure that his dissertation on the topic “Discourse on the combination of alcohol with water” had nothing to do with vodka and considered alcohol concentrations from 70 degrees. With all the merits of the scientist, the discovery of the periodic law of chemical elements - one of the fundamental laws of nature, brought him the widest fame.

There is a legend according to which the scientist dreamed of the periodic system, after which he only had to finalize the idea that had appeared. But, if everything were so simple .. This version of the creation of the periodic table, apparently, is nothing more than a legend. When asked how the table was opened, Dmitry Ivanovich himself answered: “ I’ve been thinking about it for maybe twenty years, and you think: I sat and suddenly ... it’s ready. ”

In the middle of the nineteenth century, attempts to streamline the known chemical elements (63 elements were known) were simultaneously undertaken by several scientists. For example, in 1862 Alexandre Émile Chancourtois placed the elements along a helix and noted the cyclical repetition of chemical properties.

Chemist and musician John Alexander Newlands proposed his version of the periodic table in 1866. An interesting fact is that in the arrangement of the elements the scientist tried to discover some mystical musical harmony. Among other attempts was the attempt of Mendeleev, which was crowned with success.

In 1869, the first scheme of the table was published, and the day of March 1, 1869 is considered the day of the discovery of the periodic law. The essence of Mendeleev's discovery was that the properties of elements with increasing atomic mass do not change monotonously, but periodically.

The first version of the table contained only 63 elements, but Mendeleev made a number of very non-standard decisions. So, he guessed to leave a place in the table for yet undiscovered elements, and also changed the atomic masses of some elements. The fundamental correctness of the law derived by Mendeleev was confirmed very soon, after the discovery of gallium, scandium and germanium, the existence of which was predicted by scientists.

Modern view of the periodic table

Below is the table itself.

Today, instead of atomic weight (atomic mass), the concept of atomic number (the number of protons in the nucleus) is used to order elements. The table contains 120 elements, which are arranged from left to right in ascending order of atomic number (number of protons)

The columns of the table are so-called groups, and the rows are periods. There are 18 groups and 8 periods in the table.

1. The metallic properties of elements decrease when moving along the period from left to right, and increase in the opposite direction.
2. The dimensions of atoms decrease as they move from left to right along the periods.
3. When moving from top to bottom in the group, the reducing metallic properties increase.
4. Oxidizing and non-metallic properties increase along the period from left to right.

What do we learn about the element from the table? For example, let's take the third element in the table - lithium, and consider it in detail.

First of all, we see the symbol of the element itself and its name under it. In the upper left corner is the atomic number of the element, in the order in which the element is located in the table. The atomic number, as already mentioned, is equal to the number of protons in the nucleus. The number of positive protons is usually equal to the number of negative electrons in an atom (with the exception of isotopes).

The atomic mass is indicated under the atomic number (in this version of the table). If we round the atomic mass to the nearest integer, we get the so-called mass number. The difference between the mass number and the atomic number gives the number of neutrons in the nucleus. Thus, the number of neutrons in a helium nucleus is two, and in lithium - four.

So our course "Mendeleev's Table for Dummies" has ended. In conclusion, we invite you to watch a thematic video, and we hope that the question of how to use the periodic table of Mendeleev has become more clear to you. We remind you that learning a new subject is always more effective not alone, but with the help of an experienced mentor. That is why, you should never forget about the student service, which will gladly share their knowledge and experience with you.

Instruction

The periodic system is a multi-storey "house" in which a large number of apartments are located. Each "tenant" or in his own apartment under a certain number, which is permanent. In addition, the element has a "surname" or name, such as oxygen, boron or nitrogen. In addition to these data, each "apartment" or information such as relative atomic mass is indicated, which may have exact or rounded values.

As in any house, there are "entrances", namely groups. Moreover, in groups, elements are located on the left and right, forming . Depending on which side there are more of them, that side is called the main one. The other subgroup, respectively, will be secondary. Also in the table there are "floors" or periods. Moreover, the periods can be both large (consist of two rows) and small (they have only one row).

According to the table, you can show the structure of the atom of an element, each of which has a positively charged nucleus, consisting of protons and neutrons, as well as negatively charged electrons rotating around it. The number of protons and electrons coincides numerically and is determined in the table by the ordinal number of the element. For example, the chemical element sulfur has #16, so it will have 16 protons and 16 electrons.

To determine the number of neutrons (neutral particles also located in the nucleus), subtract its serial number from the relative atomic mass of an element. For example, iron has a relative atomic mass of 56 and a serial number of 26. Therefore, 56 - 26 = 30 protons in iron.

The electrons are located at different distances from the nucleus, forming electronic levels. To determine the number of electronic (or energy) levels, you need to look at the number of the period in which the element is located. For example, aluminum is in period 3, so it will have 3 levels.

By the group number (but only for the main subgroup), you can determine the highest valency. For example, the elements of the first group of the main subgroup (lithium, sodium, potassium, etc.) have a valence of 1. Accordingly, the elements of the second group (beryllium, magnesium, calcium, etc.) will have a valence of 2.

You can also analyze the properties of elements using the table. From left to right, the metallic properties decrease and the non-metallic properties increase. This is clearly seen in the example of period 2: it begins with an alkali metal sodium, then an alkaline earth metal magnesium, after it an amphoteric element aluminum, then non-metals silicon, phosphorus, sulfur, and the period ends with gaseous substances - chlorine and argon. In the next period, a similar dependence is observed.

From top to bottom, a pattern is also observed - metallic properties are enhanced, and non-metallic ones are weakened. That is, for example, cesium is much more active than sodium.

All names of chemical elements come from the Latin language. This is necessary, first of all, so that scientists from different countries can understand each other.

Chemical signs of the elements

Elements are usually denoted by chemical signs (symbols). At the suggestion of the Swedish chemist Berzelius (1813), chemical elements are denoted by the initial or initial and one of the subsequent letters of the Latin name of this element; The first letter is always uppercase, the second lowercase. For example, hydrogen (Hydrogenium) is denoted by the letter H, oxygen (Oxygenium) by the letter O, sulfur (Sulfur) by the letter S; mercury (Hydrargyrum) - with the letters Hg, aluminum (Aluminium) - Al, iron (Ferrum) - Fe, etc.

Rice. 1. Table of chemical elements with names in Latin and Russian.

Russian names of chemical elements are often Latin names with modified endings. But there are also many elements whose pronunciation differs from the Latin source. These are either native Russian words (for example, iron), or words that are a translation (for example, oxygen).

Chemical nomenclature

Chemical nomenclature - the correct name of chemicals. The Latin word nomenclatura translates as "a list of names, titles"

At an early stage in the development of chemistry, arbitrary, random names (trivial names) were given to substances. Volatile liquids were called alcohols, they included "hydrochloric alcohol" - an aqueous solution of hydrochloric acid, "silitry alcohol" - nitric acid, "ammonia alcohol" - an aqueous solution of ammonia. Oily liquids and solids were called oils, for example, concentrated sulfuric acid was called "vitriol oil", arsenic chloride - "arsenic oil".

Sometimes substances were named after their discoverer, for example, "Glauber's salt" Na 2 SO 4 * 10H 2 O, discovered by the German chemist I. R. Glauber in the 17th century.

Rice. 2. Portrait of I. R. Glauber.

The ancient names could indicate the taste of substances, color, smell, appearance, medical effect. One substance sometimes had several names.

By the end of the 18th century, no more than 150-200 compounds were known to chemists.

The first system of scientific names in chemistry was developed in 1787 by a commission of chemists headed by A. Lavoisier. Lavoisier's chemical nomenclature served as the basis for the creation of national chemical nomenclatures. In order for chemists from different countries to understand each other, the nomenclature must be unified. At present, the construction of chemical formulas and names of inorganic substances is subject to a system of nomenclature rules created by a commission of the International Union of Pure and Applied Chemistry (IUPAC). Each substance is represented by a formula, in accordance with which the systematic name of the compound is built.

Rice. 3. A. Lavoisier.

What have we learned?

All chemical elements have Latin roots. Latin names of chemical elements are generally accepted. In Russian, they are transferred using tracing or translation. however, some words have an original Russian meaning, such as copper or iron. Chemical nomenclature is subject to all chemical substances consisting of atoms and molecules. for the first time the system of scientific names was developed by A. Lavoisier.

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If the periodic table seems difficult for you to understand, you are not alone! Although it can be difficult to understand its principles, learning to work with it will help in the study of natural sciences. To get started, study the structure of the table and what information can be learned from it about each chemical element. Then you can start exploring the properties of each element. And finally, using the periodic table, you can determine the number of neutrons in an atom of a particular chemical element.

Steps

Part 1

Table structure

The periodic table, or periodic table of chemical elements, begins at the top left and ends at the end of the last line of the table (bottom right). The elements in the table are arranged from left to right in ascending order of their atomic number. The atomic number tells you how many protons are in one atom. In addition, as the atomic number increases, so does the atomic mass. Thus, by the location of an element in the periodic table, you can determine its atomic mass.

1. As you can see, each next element contains one more proton than the element preceding it. This is obvious when you look at the atomic numbers. Atomic numbers increase by one as you move from left to right. Since the elements are arranged in groups, some table cells remain empty.

   • For example, the first row of the table contains hydrogen, which has atomic number 1, and helium, which has atomic number 2. However, they are on opposite ends because they belong to different groups.

2. Learn about groups that include elements with similar physical and chemical properties. The elements of each group are located in the corresponding vertical column. As a rule, they are indicated by the same color, which helps to identify elements with similar physical and chemical properties and predict their behavior. All elements of a particular group have the same number of electrons in the outer shell.

   • Hydrogen can be attributed both to the group of alkali metals and to the group of halogens. In some tables it is indicated in both groups.
   • In most cases, the groups are numbered from 1 to 18, and the numbers are placed at the top or bottom of the table. Numbers can be given in Roman (eg IA) or Arabic (eg 1A or 1) numerals.
   • When moving along the column from top to bottom, they say that you are "browsing the group".

3. Find out why there are empty cells in the table. Elements are ordered not only according to their atomic number, but also according to groups (elements of the same group have similar physical and chemical properties). This makes it easier to understand how an element behaves. However, as the atomic number increases, elements that fall into the corresponding group are not always found, so there are empty cells in the table.

   • For example, the first 3 rows have empty cells, since transition metals are found only from atomic number 21.
   • Elements with atomic numbers from 57 to 102 belong to the rare earth elements, and they are usually placed in a separate subgroup in the lower right corner of the table.

4. Each row of the table represents a period. All elements of the same period have the same number of atomic orbitals in which electrons are located in atoms. The number of orbitals corresponds to the period number. The table contains 7 rows, that is, 7 periods.

   • For example, the atoms of the elements of the first period have one orbital, and the atoms of the elements of the seventh period have 7 orbitals.
   • As a rule, periods are indicated by numbers from 1 to 7 on the left of the table.
   • As you move along a line from left to right, you are said to be "scanning through a period".

5. Learn to distinguish between metals, metalloids and non-metals. You will better understand the properties of an element if you can determine what type it belongs to. For convenience, in most tables, metals, metalloids and non-metals are indicated by different colors. Metals are on the left, and non-metals are on the right side of the table. Metalloids are located between them.

   Part 2

   Element designations

   1. Each element is designated by one or two Latin letters. As a rule, the element symbol is shown in large letters in the center of the corresponding cell. A symbol is an abbreviated name for an element that is the same in most languages. When doing experiments and working with chemical equations, the symbols of the elements are commonly used, so it is useful to remember them.

      • Typically, element symbols are shorthand for their Latin name, although for some, especially recently discovered elements, they are derived from the common name. For example, helium is denoted by the symbol He, which is close to the common name in most languages. At the same time, iron is designated as Fe, which is an abbreviation of its Latin name.

   2. Pay attention to the full name of the element, if it is given in the table. This "name" of the element is used in normal texts. For example, "helium" and "carbon" are the names of the elements. Usually, though not always, the full names of the elements are given below their chemical symbol.

      • Sometimes the names of the elements are not indicated in the table and only their chemical symbols are given.

   3. Find the atomic number. Usually the atomic number of an element is located at the top of the corresponding cell, in the middle or in the corner. It can also appear below the symbol or element name. Elements have atomic numbers from 1 to 118.

      • The atomic number is always an integer.

   4. Remember that the atomic number corresponds to the number of protons in an atom. All atoms of an element contain the same number of protons. Unlike electrons, the number of protons in the atoms of an element remains constant. Otherwise, another chemical element would have turned out!

      • The atomic number of an element can also be used to determine the number of electrons and neutrons in an atom.

   5. Usually the number of electrons is equal to the number of protons. The exception is the case when the atom is ionized. Protons have a positive charge and electrons have a negative charge. Since atoms are usually neutral, they contain the same number of electrons and protons. However, an atom can gain or lose electrons, in which case it becomes ionized.

      • Ions have an electrical charge. If there are more protons in the ion, then it has a positive charge, in which case a plus sign is placed after the element symbol. If an ion contains more electrons, it has a negative charge, which is indicated by a minus sign.
      • The plus and minus signs are omitted if the atom is not an ion.