Name: how valence electrons shape the periodic table
Uploaded: 2020-09-03T13:38:28.000Z
Duration: 4 min
Channel: JoVE

K12 Standards

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Chemistry

Matter and its Interactions

PS.Chm.2.1

Periodic Classification of the Elements

原子の一番外側の殻を 占める電子は価電子であり 内側の主エネルギー準位を 占める電子は 核電子です 3s1電子配置の ナトリウム原子は3つの 主エネルギー準位を 持っています 2s22p6の完全な 内側主エネルギー準位を見ると 10個の中心電子があり それに 続いて残りの1個の電子を含む 3番目の 外側主エネルギー準位があります したがって ナトリウムは 1つの価電子を持っています 同様に 塩素は 10個のコア電子と 7個の価電子を持っています 価電子は原子核から 最も遠くにあり 最もゆるやかに 保持されています そのため 価電子は最も 失いやすく 共有しやすい電子で 化学結合において重要な 役割を果たしています 同じ数の価電子を持つ元素は 現代の周期表の配置から 分かるように 似たような 化学的性質を示します 主要元素の場合 文字の付いた群番号は 価電子の数に等しく 行番号はその元素の 最高主量子数に 等しくなります グループ内の各元素は 結合のために利用可能な 電子の数が同じです 属の下の方では 主量子数は1つ増えますが 価電子の数は 変わりません 周期表の左端の 2つの列がsブロックを 構成しています これらの元素では 最後の電子がs軌道に入る 水素を除く第1族元素は アルカリ金属と呼ばれ 価電子が1個しかないため 非常に反応性が高い元素です グループ2の元素は 価電子殻に2つの電子を持つ アルカリ土類金属です 右端の6本の列が pブロックを形成しています これらの元素の価電子殻は 完全にs軌道を占有しており 最後の電子はp軌道に入ります 3群Aから8群Aまでは p軌道に入る電子の数が 1個増えます 希ガスは sブロックに属し 電子が2個しかない ヘリウムを除いて 8個の価電子を 持っています dブロックは sブロックと pブロックの間にある 10本の列で 構成されています これらの元素は 遷移金属と呼ばれています 最後の電子は 列番号より 1つ少ない主殻番号の d軌道に入ります 4列目には3個のd軌道が入り 5列目には 4個のd軌道が入ります 内部遷移元素は fブロックを構成し 最後の電子がf軌道に入ります 各行を横切る f軌道の主量子数は 列番号よりも2つ少なくなります 第6列では 4つのf軌道が充填され 第7列では 5つのf軌道が充填されます 内部遷移元素は ランタニド系列と アクチニド系列に 配置されています 各ブロックの列数は そのブロックのサブレベルで どれだけの電子を 充填できるかを示しています sブロックの2列は 2個の電子を持つs軌道に対応し pブロックの6列は6個の 電子を持つ3個のp軌道を表し dブロックの10列は それぞれ2個の電子を持つ5個の d軌道に対応します 最後に fブロックは 7個のf軌道の 最大容量を示す14列で 構成されています

元素の周期的分類

周期表は、原子番号の大きい順に原子を並べたもので、同じ化学的性質を持つ元素が周期的に繰り返されます。周期表に電子配置を加えると、これらの元素の外殻の電子配置が似たものが周期的に繰り返されることになります。価電子は、原子の外殻にあるため、化学反応において最も重要な役割を果たします。外殻電子は原子の電子の中で最もエネルギーが高く、内殻電子よりも失われやすく、共有されやすいです。また、価電子は、元素のいくつかの物理的特性を決定する要因でもあります。 
 
 横の列は周期と呼ばれます。1周期の間に、連続する各元素は、原子核に陽子を1個追加し、価電子を1個追加します。縦の列は族です。アルカリ金属のリチウムとナトリウムはそれぞれ1個、アルカリ土類金属のベリリウムとマグネシウムはそれぞれ2個、ハロゲンのフッ素と塩素はそれぞれ7個の価電子を持っています。元素の反応を規定するのは、価電子の喪失、獲得、共有です。同じグループの元素で化学的性質が似ているのは、同じ数の価電子を持っているからです。
 
 周期表は、原子構造が解明される以前に、元素の化学的挙動に基づいて作成されたものであることを忘れてはなりません。現在では、原子が持つ価電子の数が同じであれば、同じ族に属するという周期表の配置が理解されています。図1の色分けされた部分は、充填されている軌道によって3つに分類されています。 
 
 <img alt="Eq1" src="https://www.jovecore.com/CDNSource/lessons/1046/1046Image_1v2.png" /> 
 図 1 ：周期表のこのバージョンは、各要素の設定を示しています。 各族の設定はよく似ていることに注意。 
 
 主な族の元素は、典型元素と呼ばれることもあります。図1の青と赤で示したように、最後に加わった電子が最外殻のs軌道またはp軌道に入る元素です。このカテゴリーには、非金属元素のすべてと、半金属および多くの金属が含まれます。主群元素の価電子は、n準位が最も高いものです。例えば、ガリウム（Ga、原子番号31）の電子配置は[Ar]4s23d104p1であり、3個の価電子を含んでいます（下線部）。完全に満たされたd軌道は、価電子ではなく内殻電子としてカウントされます。 
 
 左端の2列がsブロックで、右端の6列がpブロックです。p-ブロックに属する希ガスは、2個のヘリウムを除いて、すべて8個の価電子を持っています。これらの元素は非常に安定していて、反応しません。 
 
 遷移元素または遷移金属：最後に加えられた電子がd軌道に入る金属元素です。これらの元素の価電子（最後の希ガス配置の後に付加される電子）には、nsと（n - 1）d電子が含まれます。IUPACの正式な定義では、遷移元素はd軌道が部分的に満たされたものと規定されています。したがって、完全に満たされた軌道を持つ元素（図1のZn、Cd、Hg、およびCu、Ag、Au）は、厳密には遷移元素ではありません。しかし、この用語は、dブロック全体（図1では黄色で表示）を指すことが多いです。 
 
 dブロックは10列で構成されています。各列を埋めるd軌道の主量子数は、列番号から1を引いたものに等しいです。4列目には3d軌道、5列目には4d軌道が満たされ、以下のようになります。 
 
 内部遷移元素/strong>：図1の緑色で示されます。内部遷移元素の価電子殻は、(n – 2)f、 (n – 1)d、nsの各小軌道からなります。内部遷移元素は、最後の電子がf軌道に入ることでfブロックを構成します。各列を埋めるf軌道の主量子数は、列番号から2を引いたものに等しいです。6列目には4f軌道が、7列目には5f軌道が充填されます。２つの内部遷移系があります: 
 
 <ol>
 <li>ランサナム系：ランサナム（La）からルテチウム（Lu） </li>
 <li>アクチニド系：アクチニド（ ACc）からローレンシウム（ Lr ） </li>
 </ol>
 
 ランサナムとアクチニウムは、f電子を持たない遷移金属であるにもかかわらず、系の他のメンバーとの類似性から、系の名前に含まれて使用されています。 
 
 このテキストは <a href="https://openstax.org/books/chemistry-2e/pages/6-4-electronic-structure-of-atoms-electron-configurations">、 OpenStax Chemistry 2e のセクション 6.4 ： Electronic Structure of Atoms から引用したものです。</a>

周期表は、原子番号の増加に基づいて原子を配置し、同じ化学的性質を持つ元素が周期的に繰り返されるようにします。彼らの...

Education

JoVE Core

化学

Periodic Properties of the Elements

元素の周期的な性質

KEY TERMS AND CONCEPTS

主要用語と概念

how valence electrons shape the periodic table

The periodic table organizes elements by increasing atomic number, and it also shows why elements in the same group behave alike. As the electron configurations are placed into the table, a repeating pattern appears in the outer shells of atoms. These outer electrons are called valence electrons, and they play the biggest role in chemical reactions. They are the highest-energy electrons in an atom, so they are easier to lose or share than core electrons. Valence electrons also help determine some physical properties of elements.

The horizontal rows on the periodic table are periods. Moving across a period, each next element has one more proton in the nucleus and one more electron in the valence shell. The vertical columns are groups. Elements in the same group have the same number of valence electrons, which is why they often show similar chemical behavior. For example, lithium and sodium each have one valence electron, beryllium and magnesium each have two, and fluorine and chlorine each have seven. Because elements react by losing, gaining, or sharing valence electrons, their group placement helps predict how they will behave.

It is important to remember that the periodic table was built from chemical behavior before atomic structure was understood. Today, the pattern makes sense because elements with the same number of valence electrons are placed in the same group. The colored regions of the table also show three categories based on which orbitals are being filled. Main group elements, also called representative elements, are the elements whose last added electron enters an s or p orbital in the outermost shell. This category includes all nonmetals, the metalloids, and many metals. For main group elements, the valence electrons are the electrons with the highest n level. Gallium, for example, has the electron configuration [Ar] 4s2 3d10 4p1, so it has three valence electrons. The filled d orbitals are counted as core electrons, not valence electrons.

The two far-left columns form the s-block, and the six far-right columns form the p-block. The noble gases are part of the p-block. They usually have eight valence electrons, except helium, which has two. This helps explain why noble gases are highly stable and unreactive. Transition elements, or transition metals, are metallic elements whose last added electron enters a d orbital. Their valence electrons include the ns and (n - 1)d electrons added after the last noble gas configuration. By the official IUPAC definition, transition elements have partially filled d orbitals, so Zn, Cd, Hg, and also Cu, Ag, and Au are not technically transition elements, even though the term is often used for the whole d-block.

The d-block has 10 columns. As you move across each row, the d orbitals that fill have a principal quantum number that is one less than the row number. In the fourth row, 3d orbitals fill; in the fifth row, 4d orbitals fill; and so on. Inner transition elements form the f-block, where the last electron added enters an f orbital. Their valence shells include the (n - 2)f, the (n - 1)d, and the ns subshells. The f orbitals that fill across each row have a principal quantum number that is two less than the row number. In the sixth row, 4f orbitals fill, and in the seventh row, 5f orbitals fill. The two inner transition series are the lanthanides, from lanthanum through lutetium, and the actinides, from actinium through lawrencium. Lanthanum and actinium are included in those series because they are similar to the other members, even though they are transition metals with no f electrons.

How Valence Electrons Shape the Periodic Table

how-valence-electrons-shape-the-periodic-table

periodic classification of the elements

The periodic table organizes elements by increasing atomic number, and it also shows why elements in the same group behave alike. As the electron configurations are placed into the table, a repeating pattern appears in the outer shells of atoms. These outer electrons are called valence electrons, and they play the biggest role in chemical reactions. They are the highest-energy electrons in an atom, so they are easier to lose or share than core electrons. Valence electrons also help determine...

ionization energy

Ionization Energy Trends in the Periodic Table

Ionization energy is the energy needed to remove an electron from a gaseous atom or ion in its ground state. The first ionization energy, or IE1, removes the most loosely bound electron and forms a 1+ cation. The second ionization energy, IE2, removes the next electron, and each later ionization energy removes another electron from the atom or ion. Ionization always requires energy, so these processes are endothermic. That means ionization energy values are always positive. In general, larger...

atomic radii and effective nuclear charge

atomic-radii-and-effective-nuclear-charge

Periodic Trends in Atomic Size

Periodic trends in atomic size help explain why atoms get larger or smaller across the periodic table. Elements in the same group show similar chemical behavior because they have the same number and arrangement of valence electrons. Across a period, each new element adds one proton to the nucleus and one electron to the valence shell. Down a group, the number of valence electrons stays the same, but the principal quantum number increases by one. Atomic radius is not easy to define with perfect...

ionic radii

How Ionic Charge Changes Ion Size

Ionic radius describes the size of an ion. It changes when an atom gains or loses electrons. Cations are positive ions with fewer electrons than the parent atom, and they are smaller than the atoms they come from. Aluminum shows this pattern clearly. A neutral aluminum atom has a covalent radius of 118 pm, while Al3+ has an ionic radius of 68 pm. When electrons are removed from the outer valence shell, the remaining core electrons feel a stronger effective nuclear charge, or Zeff. That pull...

electron affinity

Electron Affinity Trends on the Periodic Table

Electron affinity is the energy change that happens when a gaseous atom gains an electron and becomes a negative ion, or anion. For many elements, this process releases energy, so the electron affinity value is negative. For some elements, energy must be added instead, so the value is positive. Electron affinity also applies when more than one electron is added. The second electron affinity is the energy change for adding an electron to an anion to make a 2− ion. Later electron affinities...

alkali metals

Alkali Metals: Reactivity Trends

Alkali metals are Group 1 elements with one valence electron. They are soft, shiny metallic solids that are malleable, ductile, and good conductors of heat and electricity. Their melting points are unusually low for metals and drop as you move down the group. Density generally increases down the group, except for potassium. The trend in atomic size helps explain their behavior. Moving from lithium to cesium, each element has a higher principal quantum number, so the outer electron is farther...

halogens

Halogens: Trends and Reactions

Halogens are Group 17 nonmetals that show clear trends in structure and reactivity. At room temperature, fluorine and chlorine are gases, bromine is a liquid, and iodine is a solid. Astatine is highly unstable and radioactive, so most of its properties are still unknown because it has a very short half-life. Tennessine is a synthetic element that is also predicted to belong to this group. These elements do not usually exist as single atoms. Instead, they form diatomic molecules, which means...

noble gases

Noble Gases: Sources, Uses, and Reactions

Noble gases are the group 18 elements helium, neon, argon, krypton, xenon, and radon. They were called “noble” because they were once thought to be nonreactive. That idea changed in 1962, when Dr. Neil Bartlett at the University of British Columbia showed that this assumption was not fully correct. These gases occur in very small amounts in the atmosphere. Some natural gas contains 1–2% helium by mass. Helium is separated from natural gas by removing the condensable components, which leaves...

key terms and concepts

Learn how valence electrons explain periodic table groups, blocks, and element behavior, including main group, transition, lanthanide, and actinide elements.

How Valence Electrons Shape the Periodic Table | JoVE K12

chemistry

JoVE Core 化学は、簡潔で理解しやすいアニメーションビデオレッスンを使用して、一般的な化学の概念を生き生きとしたものにします。さらに、活動する科学者のビデオでは、現在世界中の実験室で行われている古典的そして独創的な研究・実験をお見せします。

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Periodic trends of the elements

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Periodic Table Trends: Atomic Radii, Ionization, and Electronegativity

Scientific Laws and Theories

Scientific Laws

In science, a law is defined as a concise, verbal or mathematical, statement that summarizes a vast number of experimental observations. ...

The Scientific Method

Chemistry is an empirical science. Scientists often pose questions to understand the chemistry in everyday life and seek answers to these questions. To ...

Classifying Matter by State

Chemistry is the study of matter and the changes it undergoes. Matter is anything that has mass and occupies space. Matter is all around us; the air, ...

Classifying Matter by Composition

Matter: Pure Substances and Mixtures
According to its composition, the matter can be classified into two broad categories &mdash; pure substances and ...

The Atomic Theory of Matter

The earliest recorded discussion of the basic structure of matter comes from ancient Greek philosophers. Leucippus and Democritus argued that all matter ...

Subatomic Particles

Dalton was only partially correct about the particles that make up matter. All matter is composed of atoms, and atoms are composed of three smaller ...

Elements: Chemical Symbols and Isotopes

A chemical symbol is an abbreviation used to indicate an element or an atom of an element. For example, the symbol for mercury is Hg. The same symbol is ...

Use models to explain how the scientific understanding of atomic structure has evolved.

PS.Chm.1.1

Radioactivity and Nuclear Equations

Nuclear chemistry is the study of reactions that involve changes in nuclear structure. The nucleus of an atom is composed of protons and, except for ...

Types of Radioactivity

The most common types of radioactivity are &#945; decay, &#946; decay, &#947; decay, neutron emission, and electron capture.
Alpha (&#945;) decay is the ...

Nuclear Stability

Protons and neutrons, collectively called nucleons, are packed together tightly in a nucleus. With a radius of about 10&#8722;15 meters, a nucleus is ...

Nuclear Binding Energy

The difference between the calculated and experimentally measured masses is known as the mass defect of the atom. In the case of helium-4, the mass defect ...

Radioactive Decay and Radiometric Dating

Radioactivity is a spontaneous disintegration of an unstable nuclide and is a random process, as all the nuclei in the sample do not decay simultaneously. ...

Nuclear Fission

Many heavier elements with smaller binding energies per nucleon can decompose into more stable elements that have intermediate mass numbers and larger ...

Nuclear Power

Controlled nuclear fission reactions are used to generate electricity. Any nuclear reactor that produces power via the fission of uranium or plutonium by ...

Nuclear Fusion

The process of converting very light nuclei into heavier nuclei is also accompanied by the conversion of mass into large amounts of energy, a process ...

Nuclear Transmutation

Nuclear transmutation is the conversion of one nuclide into another. It can occur by the radioactive decay of a nucleus, or the reaction of a nucleus with ...

Use models to compare nuclear reactions including alpha decay, beta decay and gamma decay; nuclear fusion and nuclear fission.

PS.Chm.1.2

Atomic Orbitals

An atomic orbital represents the three-dimensional regions in an atom where an electron has the highest probability to reside. The radial distribution ...

The Pauli Exclusion Principle

The arrangement of electrons in the orbitals of an atom is called its electron configuration. We describe an electron configuration with a symbol that ...

The Energies of Atomic Orbitals

In an atom, the negatively charged electrons are attracted to the positively charged nucleus. In a multielectron atom, electron-electron repulsions are ...

The Aufbau Principle and Hund's Rule

To determine the electron configuration for any particular atom, we can build the structures in the order of atomic numbers. Beginning with hydrogen, and ...

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Electron Configuration of Multielectron Atoms

The alkali metal sodium (atomic number 11) has one more electron than the neon atom. This electron must go into the lowest-energy subshell available, the ...

Use models to explain how electrons are distributed in atoms.

PS.Chm.1.3

The periodic table arranges atoms based on increasing atomic number so that elements with the same chemical properties recur periodically. When their ...

The Periodic Table

As early chemists discovered more elements, they realized that various elements could be grouped by their similar chemical behaviors. One such grouping ...

Atomic Mass

Atoms &mdash; and the protons, neutrons, and electrons that compose them &mdash; are extremely small. For example, a carbon atom weighs less than 2 ...

Molar Mass

The identity of a substance is defined not only by the types of atoms or ions it contains but by the quantity of each type of atom or ion. For example, ...

Use the Periodic Table as a model to predict the relative properties of elements based on the pattern of valence electrons in the outermost energy levels of atoms.

Atomic Radii and Effective Nuclear Charge

The elements in groups of the periodic table exhibit similar chemical behavior. This similarity occurs because the members of a group have the same number ...

Ionic Radii

Ionic radius is the measure used to describe the size of an ion. A cation always has fewer electrons and the same number of protons as the parent atom; it ...

Ionization Energy

The amount of energy required to remove the most loosely bound electron from a gaseous atom in its ground state is called its first ionization energy ...

Electron Affinity

The electron affinity (EA) is the energy change for adding an electron to a gaseous atom to form an anion (negative ion).



This process can be either ...

Construct an explanation to infer the atomic size, reactivity, electronegativity, and ionization energy of an element based on its position in the Periodic Table.

PS.Chm.2.2

Types of Chemical Bonds

Chemical bonding theories were pioneered by American chemist Gilbert&#xA0;N. Lewis. He developed a model called the Lewis model to explain the type and ...

Lewis Symbols and the Octet Rule

Chemical bonds are complex interactions between two or more atoms or ions, which reduce the potential energy of the molecule. Gilbert N. Lewis developed a ...

Ionic Bonding and Electron Transfer

Ions are atoms or molecules bearing an electrical charge. A cation (a positive ion) forms when a neutral atom loses one or more electrons from its valence ...

The Born-Haber Cycle

Lattice Energy&#xA0;

An ionic compound is stable because of the electrostatic attraction between its positive and negative ions. The lattice energy of a ...

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Trends in Lattice Energy: Ion Size and Charge

An ionic compound is stable because of the electrostatic attraction between its positive and negative ions. The lattice energy of a compound is a measure ...

Analyze and interpret data to explain the mechanisms and properties of the two main types of intramolecular (ionic and covalent) bonds.

PS.Chm.3.1

Analyze the structure of atoms and isotopes.

How Valence Electrons Shape the Periodic Table

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