Name: alkali metals: reactivity trends
Uploaded: 2020-09-03T13:38:28.000Z
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Physical Science

Matter and its Interactions

PS.PSc.1.6

Alkali Metals

الفلزات القلوية هي عناصر المجموعة 1،بما في ذلك الليثيوم،الصوديوم،البوتاسيوم،الروبيديوم،السيزيوم،وفرانسيوم. الفرانسيوم مشع وليس له نظائر مستقرة. جميع المعادن القلوية ناعمة بشكل غير عادي وتتشارك مع المعادن في الخواص،مثل قابلية توصيل الكهرباء والحرارة العالية.بالتحرك أسفل المجموعة فإنّالكتلة والكثافة ونصف القطر الذري تزداد،بينما نقاط الانصهار وطاقات التأين تنخفض. التكوين الإلكتروني لهذه العناصر يتضمن أن غلاف التكافؤ يحتوي على إلكترون واحد فقط. طاقات التأين المنخفضة تشير على أن المعادن القلوية تفقد الإلكترونات بسهولة لتصبح كاتيونات بتكوين غاز نبيل.وهذا يفسر أيضًا سبب كون الفلزات القلوية عوامل اختزال ممتازة،مع كون الليثيوم أقلها تفاعلاًوالسيزيوم أكثرها. تتفاعل المعادن القلوية بقوة مع اللافلزات،مثل الهالوجينات لتشكيل الأملاح. تفاعل فلز الصوديوم مع غاز الكلور طارد للحرارة بدرجة عالية ويطلق شرارات وحرارة.تزداد شدة التفاعل بإتجاه أسفل المجموعة،حيث طاقات تأين المعادن القلوية تنخفض. تتفاعل المعادن القلوية بشدة مع الماء لتوليد غاز الهيدروجين ومحلول هيدروكسيد فلزي قلوي مثل هيدروكسيد البوتاسيوم،وهي قاعدة تستخدم غالبًا في صناعة الصابون. يصبح رد الفعل أكثر عنفًا للمعادن القلوية الأكثر ثقلاًنظرا لطاقات التأين المنخفضة الخاصة بهم.الحرارة الناتجة أثناء التفاعل،قد تشعل غاز الهيدروجين المتحرر،مما يؤدي الى اضرام النار أو الانفجار. يمكن أن تتفاعل المعادن القلوية أيضًا مع الهيدروجين لتشكيل هيدرات الفلزات القلوية،وغالبًا ما تستخدم كقواعد قوية. في هذا التفاعل،تكتسب ذرة الهيدروجين إلكترونًا وهو موجود مثل أيون الهيدريد.بسبب قابليتها العالية للتفاعل،فإنّالمعادن القلوية تتأكسد بسهولة عند التعرض للهواء،وبالتالي يتم تخزينها في زيوت معدنية. عندما توضع الأملاح المعدنية القلوية في اللهب تختزل إلى ذراتها المعدنية الغازية،تنبعث منها ألوان مميزة. تثير الحرارة إلكترون التكافؤ إلى مستوى طاقة أعلى.عندما تعود الإلكترونات المثارة إلى الحالة الأساسية،تنبعث الطاقة في شكل إشعاع في المنطقة المرئية. طيف الانبعاث لكل عنصر فريد من نوعه ويستخدم لتحديد العنصر نوعيًا.

المعادن القلوية

عناصر المجموعة 1 عبارة عن مواد صلبة معدنية ناعمة ولامعة. فهي مرنة وقابلة للطرق وجيدة التوصيل للحرارة والكهرباء. تكون نقاط انصهار المعادن القلوية منخفضة بشكل غير عادي بالنسبة للمعادن وتقل عند النزول في المجموعة الدورية. تنخفض الكثافة أيضاً في نفس الاتجاه ، باستثناء البوتاسيوم (الجدول 1). الجدول 1: خصائص الفلزات القلوية <table style = "margin-left: auto؛ margin-right: auto؛"><tbody style = "border: 1px solid black؛"><tr><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> العنصر </td><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> تكوين الإلكترون </td><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> نصف القطر الذري (pm) </td><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> IE 1 (كيلوجول/مول) </td><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> درجة الانصهار (&deg؛C) </td><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> الكثافة عند 25 درجة مئوية (غ/سم 3 ) < / TD></tr><tr><td style = "color: black؛ border: 1px Solid black؛ text-align: center؛"> Li </td><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> [He] 2 s 1 </td><td style = "color: black؛ border: 1px Solid black؛ text-align: center؛"> 152 </td><td style = "color: black؛ border: 1px Solid black؛ text-align: center؛"> 520 </td><td style = "color: black؛ border: 1px Solid black؛ text-align: center؛"> 181 </td><td style = "color: black؛ border: 1px Solid black؛ text-align: center؛"> 0.53 </td></tr><tr><td style = "color: black؛ border: 1px Solid black؛ text-align: center؛"> Na </td><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> [Ne] 3 s 1 </td><td style = "color: black؛ border: 1px Solid black؛ text-align: center؛"> 186 </td><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> 496 </td><td style = "color: black؛ border: 1px Solid black؛ text-align: center؛"> 98 </td><td style = "color: black؛ border: 1px Solid black؛ text-align: center؛"> 0.97 </td></tr><tr><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> K </td><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> [Ar] 4 s 1 </td><td style = "color: black؛ border: 1px Solid black؛ text-align: center؛"> 227 </td><td style = "color: black؛ border: 1px Solid black؛ text-align: center؛"> 420 </td><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> 64 </td><td style = "color: black؛ border: 1px Solid black؛ text-align: center؛"> 0.86 </td></tr><tr><td style = "color: black؛ border: 1px Solid black؛ text-align: center؛"> Rb </td><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> [Kr] 5 s 1 </td><td style = "color: black؛ border: 1px Solid black؛ text-align: center؛"> 248 </td><td style = "color: black؛ border: 1px Solid black؛ text-align: center؛"> 400 </td><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> 39 </td><td style = "color: black؛ border: 1px Solid black؛ text-align: center؛"> 1.53 </td></tr><tr><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> Cs </td><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> [Xe] 6 s 1 </td><td style = "color: black؛ border: 1px Solid black؛ text-align: center؛"> 265 </td><td style = "color: black؛ border: 1px Solid black؛ text-align: center؛"> 380 </td><td style = "color: black؛ border: 1px Solid black؛ text-align: center؛"> 29 </td><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> 1.93 </td></tr></tbody></table> عند النزول في المجموعة الدورية، يزيد العدد الكمي الأساسي n بمقدار واحد لكل عنصر. وهكذا، تبتعد الإلكترونات الخارجية عن النواة، ويزداد نصف القطر الذري من الليثيوم إلى السيزيوم. 
 يوضح تكوين الإلكترون لهذه العناصر أن غلاف التكافؤ يحتوي على إلكترون واحد فقط (الجدول 1). ينتج عن فقدان هذا الإلكترون كاتيون بتكوين الغاز النبيل. وبالتالي، فإن المعادن القلوية لديها ميل كبير للتخلي عن هذا الإلكترون ولها طاقات تأين أوليّة منخفضة، وهي تقل بالنزول في المجموعة الدورية. قدرتها على فقدان الإلكترون بسهولة تجعلها عوامل اختزال عالية التفاعل وممتازة. تتفاعل المعادن القلوية بقوة مع اللامعادن، مثل الهالوجينات. تفاعل الصوديوم والكلور لإنتاج كلوريد الصوديوم طارد للحرارة. تتفاعل المعادن القلوية أيضاً بعنف مع الماء، وينتج غاز الهيدروجين وهيدروكسيد معدن قلوي. يمكن أن تؤدي الحرارة الناتجة أثناء التفاعل إلى إشتعال غاز الهيدروجين، مما يؤدي إلى حدوث انفجار. يصبح كلا التفاعلين أكثر إصداراً للحرارة للمعادن القلوية الثقيلة بسبب طاقات التأين المنخفضة. إن التعرض للهواء، حيث يتم التفاعل مع الأكسجين لتكوين أكاسيد، يقوم باختزال اللمعان المعدني للمعادن القلوية. يتفاعل الليثيوم مع الأكسجين ليعطي أكسيد الليثيوم، بينما تشكل المعادن القلوية الأخرى مثل الصوديوم أكاسيد و بيروكسيدات. يحتوي أيون البيروكسيد على رابطة تساهمية أكسجين-أكسجين واحدة وهو متقبل قوي لأيون الهيدروجين، مما يجعل بيروكسيدات المعادن القلوية قواعد قوية. تنتج المعادن القلوية مثل البوتاسيوم والروبيديوم والسيزيوم أيضاً أكسيدات فائقة. تتميز الأكسيدات الفائقة بوجود O2−. أكسيد البوتاسيوم الفائق مادة صلبة صفراء تتحلل عند 560°C. هذا النص مقتبس من <a href="https://openstax.org/books/chemistry-2e/pages/6-5-periodic-variations-in-element-properties">Openstax, Chemistry 2e, Section 6.5: Periodic Variations in Element Properties.</a>

عناصر المجموعة 1 هي مواد صلبة معدنية ناعمة ولامعة. إنها موصلات مرنة ومطيلة وجيدة للحرارة والكهرباء. نقاط انصهار ...

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Periodic Properties of the Elements

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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 from the nucleus and the atomic radius increases. Their electron configurations show a single electron in the valence shell. When that electron is lost, the atom forms a cation with a noble gas configuration.

Because they give up that outer electron so easily, alkali metals have low first ionization energies and are highly reactive. Their first ionization energies decrease down the group, which makes the heavier elements even more reactive. They are also strong reducing agents. In reactions with nonmetals such as halogens, they react vigorously. A common example is sodium reacting with chlorine to form sodium chloride, and the reaction releases heat.

Alkali metals also react violently with water. These reactions produce hydrogen gas and an alkali metal hydroxide. The heat can ignite the hydrogen gas, which may lead to an explosion. The reactions become more exothermic for the heavier alkali metals because their ionization energies are lower.

Exposure to air causes alkali metals to react with oxygen and lose their metallic luster. Lithium forms lithium oxide. Other alkali metals such as sodium can form oxides and peroxides. A peroxide contains a single oxygen-oxygen covalent bond and acts as a strong base because it strongly accepts hydrogen ions. Potassium, rubidium, and cesium can also form superoxides, which contain O2- . Potassium superoxide is a yellow solid that decomposes at 560 °C.

Alkali Metals: Reactivity Trends

periodic classification of the elements

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...

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 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

Explore how alkali metals change down Group 1, from atomic size and ionization energy to reactions with water, oxygen, and halogens.

Alkali Metals: Reactivity Trends | JoVE K12

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Electron Configuration and Chemical Properties

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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 ...

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Colloids

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Phase Transitions: Vaporization and Condensation

The physical form of a substance changes on changing its temperature. For example, raising the temperature of a liquid causes the liquid to vaporize ...

Vapor Pressure

When a liquid vaporizes in a closed container, gas molecules cannot escape. As these gas phase molecules move randomly about, they will occasionally ...

Clausius-Clapeyron Equation

The equilibrium between a liquid and its vapor depends on the temperature of the system; a rise in temperature causes a corresponding rise in the vapor ...

Phase Transitions: Melting and Freezing

Heating a crystalline solid increases the average energy of its atoms, molecules, or ions, and the solid gets hotter. At some point, the added energy ...

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Phase Transitions: Sublimation and Deposition

Some solids can transition directly into the gaseous state, bypassing the liquid state, via a process known as sublimation. At room temperature and ...

Heating and Cooling Curves

When a substance&#8212;isolated from its environment&#8212;is subjected to heat changes, corresponding changes in temperature and phase of the substance ...

Phase Diagrams

A phase diagram combines plots of pressure versus temperature for the liquid-gas, solid-liquid, and solid-gas phase-transition equilibria of a substance. ...

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Physical and Chemical Properties of Matter

The characteristics that enable us to distinguish one substance from another are called properties.

Physical Properties of Matter

A physical property is ...

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Molecular Comparison of Gases, Liquids, and Solids

Particles in a solid are tightly packed together (fixed shape) and often arranged in a regular pattern; in a liquid, they are close together with no ...

Intermolecular vs Intramolecular Forces

Intermolecular forces (IMF) are electrostatic attractions arising from charge-charge interactions between molecules. The strength of the intermolecular ...

Intermolecular Forces

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Comparing Intermolecular Forces: Melting Point, Boiling Point, and Miscibility

Intermolecular forces are attractive forces that exist between molecules. They dictate several bulk properties, such as melting points, boiling points, ...

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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 ...

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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 ...

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Following the work of Ernest Rutherford and his colleagues in the early twentieth century, the picture of atoms consisting of tiny dense nuclei surrounded ...

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The de Broglie Wavelength

In the macroscopic world, objects that are large enough to be seen by the naked eye follow the rules of classical physics. A billiard ball moving on a ...

The Uncertainty Principle

Werner Heisenberg considered the limits of how accurately one can measure properties of an electron or other microscopic particles. He determined that ...

Use models to interpret the data presented in Bohr diagrams and electron dot diagrams for neutral atoms of elements 1 through 18.

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Ions and Ionic Charges

In ordinary chemical reactions, the nucleus &mdash; which contains the protons and neutrons of each atom and thus identifies the element &mdash; remains ...

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PS.PSc.1.5

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 ...

Periodic Classification of the Elements

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

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 ...

Group 1 elements are soft and shiny metallic solids. They are malleable, ductile, and good conductors of heat and electricity. The melting points of the ...

Halogens

Group 17 elements, known as halogens, are nonmetals. At room temperature, fluorine and chlorine are gases, bromine is a liquid, and iodine a solid. ...

Noble Gases


The elements in group 18 are noble gases (helium, neon, argon, krypton, xenon, and radon). They earned the name &ldquo;noble&rdquo; because they were ...

Use the Periodic Table as a model to predict the relative properties (metallic/nonmetallic character, ionic charge, and reactivity) and arrangement of elements based on the pattern of valence electrons in the outermost energy levels of atoms.

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 ...

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 ...

Covalent Bonding and Lewis Structures

Compared to ionic bonds, which results from the transfer of electrons between metallic and nonmetallic atoms, covalent bonds result from the mutual ...

Bonding in Metals

Metallic bonds are formed between two metal atoms. A simplified model to describe metallic bonding has been developed by Paul Dr&#xFC;de called the ...

Construct an explanation to classify the type of chemical bond that occurs (covalent, ionic, or metallic) in a given substance.

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Nomenclature of Alkanes

In the late 19th-century, the number of new chemical compounds discovered increased tremendously. Hence, the necessity arose to develop a naming system ...

Use models to apply International Union of Pure and Applied Chemistry (IUPAC) conventions to name and write formulas for simple compounds.

PS.PSc.2.2

Understand types, properties, and structure of matter.

Alkali Metals: Reactivity Trends

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