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The Periodic Table classification is a tool used for arranging chemical elements and their properties for easy understanding. The candidates see trends of the elements across the group and the periods. The Periodic Table also explains the trends and changes in the atomic radius, electronegativity, and metallic properties. The periodic table law says that the chemical and physical properties of the elements change regularly with the atomic number. The periodic table categorizes elements into groups and periods, making it easier to understand their electronegativity and chemical reactivity. For example, metals are found on the left, while nonmetals are found on the right. As a rule, atomic size decreases from left to right across a period, while increasing from top to bottom across a group. These laws and arrangements play an important role in the teaching and research of chemistry. History of the Periodic Table Dmitri Mendeleev, the founder of modern chemistry, arranged the elements in a periodic table in 1869, based on their atomic masses, and in this way showed that similar properties recur periodically, i.e., properties are periodic. This development helped predict future elements and left gaps that were later filled in. Modern Periodic Law In 1913, Henry Moseley based the arrangement of elements on atomic number rather than atomic mass, and thus better explained periodic functions, i.e. the periodicity of the physical and chemical properties of elements, in terms of atomic number. He resolved some of the inconsistencies in Mendeleev's table, such as the opposite arrangement of iodine and tellurium. Groups and Periods in the Periodic Table The periodic table arranges the elements into groups and periods. Groups are vertical columns in which elements have similar chemical properties, while periods are horizontal rows that show increasing atomic number. Elements in each group have the same number of outer electrons, which affects their chemical reactivity. For example, the alkali metals are found in the first group and are highly reactive. The physical and chemical properties of elements change gradually across periods. The first period contains only two elements, while the periods get longer as you move down. In each period, the atomic radius of the elements decreases from left to right, while electronegativity increases. This arrangement helps scientists predict the future behavior of the elements. Types of Elements Metals Metals are usually shiny, strong, and malleable. They are good thermal and electrical insulators and can be easily malleable. Metals include most elements, such as iron, copper, aluminum, and gold. These elements lose electrons to form positive ions and tend to be very conductive. Metals are mostly found on the left and middle of the periodic table. Non-Metals Nonmetals are usually soft, colorless, and poor conductors of heat and electricity. They are poor conductors of heat and electricity, and are mostly found in gaseous or liquid forms rather than solids, such as oxygen, nitrogen, carbon, and chlorine. These elements usually gain electrons to form negative ions and have different reactivity characteristics than metals. Nonmetals are found on the upper right of the periodic table. Metalloids Semimetals or metalloids are elements that have properties intermediate between those of metals and nonmetals. They sometimes have electrical insulation, but to a lesser degree, and can conduct electricity under certain conditions, so they are also called semiconductors. Well-known semimetals include boron, silicon, and arsenic. These elements lie on the line between metals and nonmetals in the periodic table, and their properties are very important in technology, especially computer chips and semiconductors. Trends in the Periodic Table Electronic Configuration & Periodicity The electronic configuration of elements in the periodic table affects their chemical properties. The electrons of each element are arranged in specific energy levels, which illustrate periodicity trends. For example, the number of electrons increases as you move down a group, while the outermost orbitals of elements become filled across a period. This arrangement plays an important role in understanding the temperament and reactivity of elements. Atomic Radius In the Periodic Table The atomic radius refers to the distance from the nucleus of an element to the outermost electron. In the periodic table, this radius decreases from left to right across a period, as the attractive force of the nucleus increases. However, the atomic radius increases as you move down a group, as the energy levels increase. This trend helps understand the physical properties of elements. Ionization Energy Trends of the Periodic Table Ionization energy is the energy required to remove an element's outermost electron. It increases from left to right across a period in the periodic table, as the attraction of the nucleus increases. However, ionization energy decreases as you move down a group, as the electrons move further away from the nucleus. These trends are important in understanding the chemical reactivity of elements. Electron Affinity Trends Electron affinity is the energy released when an atom of an element gains an additional electron. Electron affinity increases from left to right in the periodic table, as atoms move towards a full outer orbital and are eager to accept new electrons. Electron affinity decreases from top to bottom, as the size of the atom increases and the attraction of the nucleus to the outer electrons decreases. The halogens have the highest electron acceptors. Electronegativity Trends in the Periodic Table Electronegativity is the ability of an atom of an element to attract electrons from other atoms in a chemical bond. Electronegativity increases from left to right in the periodic table, as the atomic number increases and the attraction of the nucleus to the outer electrons increases. Electronegativity decreases from bottom to bottom, as the distance increases as new orbitals are added. Fluorine is the element with the highest electron affinity. Trends of Atomic Size Atomic size, or the size of an atom, is an important trend in the periodic table. Atomic size decreases as you move from left to right because electrons are in the same orbital, but as the atomic charge increases, they move closer to the nucleus. Atomic size increases as you move from top to bottom because new orbitals are added that move electrons away from the nucleus. That is why atoms are smaller in the upper group and larger in the lower groups. Where are metals located in the periodic table? Metals are found on the left and middle of the periodic table. They include alkali metals, alkaline earth metals, transition metals, and inner transition metals. Properties of metals include luster, ductility, and electrical insulation. Hydrogen is the only nonmetal that is placed with metals. What are the vertical columns of the periodic table called? The vertical columns of the periodic table are called groups. The chemical properties of the elements in each group are similar because they have the same number of electrons in their outer shells. For example, the alkali metals in the first group are highly reactive. What is the basis for the arrangement of elements on the periodic table? Elements are arranged in the periodic table by their atomic number (number of protons). In addition, elements are divided into groups and periods based on their similarity in their electronic configuration and chemical properties. This arrangement helps to understand the trends of the elements. What is a group in the periodic table? Groups are vertical columns in the periodic table in which elements have the same number of outer electrons. These elements show similar chemical properties. For example, all elements in group 7 (halogens) are highly reactive and form salts. What is the periodic table of elements? The periodic table is an organized arrangement of elements in which they are divided into groups and periods based on their atomic number, electronic configuration, and chemical properties. This table helps scientists understand the nature of the elements and the relationships between them. It was invented by Dmitri Mendeleev. How do ionization energy, atomic radius, and electronegativity change across periods and groups? As you move from left to right across periods (horizontal rows) in the periodic table, ionization energy and electronegativity increase, while atomic radius decreases. This is because the attraction of the nucleus increases. As you move from top to bottom across groups (vertical columns), ionization energy decreases, atomic radius increases, and electronegativity decreases because the number of electrons and energy levels increase. What is the difference between electron gain enthalpy and electronegativity? Electron gain enthalpy is the energy released or absorbed by an atom of an element when it gains or loses an electron. Electronegativity describes the ability of an element to attract electrons. The former is related to energy, while the latter describes the ability to attract electrons. Development of the modern periodic table (Lewisier, Newlands, Mendeleev, Moseley) In the development of the periodic table, Leviezer first grouped the elements. Newlands arranged the elements on the principle of octets. Mendeleev arranged the elements in the table based on their atomic weight and left blank spaces. Later, Moseley gave the table a modern form based on atomic number, which is still used today. What is the importance of atomic number in the periodic table? The atomic number (number of protons) is the basic principle of the arrangement of elements in the periodic table. It uniquely identifies the element and affects its chemical properties. The elements in the table are arranged in increasing order of atomic number, which makes it easier to understand their electronic configuration and distance trends. Which elements exist in the form of diatomic molecules at room temperature? At room temperature, hydrogen (H₂), nitrogen (N₂), oxygen (O₂), fluorine (F₂), chlorine (Cl₂), bromine (Br₂), and iodine (I₂) occur as diatomic molecules. These elements form pairs for their stability. What is the meaning and importance of groups and periods in the periodic table? Groups (vertical columns) consist of elements that have the same number of outer electrons, which causes them to have similar chemical properties. Periods (horizontal rows) arrange the elements in order of atomic number, where each new period marks the beginning of a new energy level. This arrangement helps in understanding the physical and chemical properties of the elements. Why do atoms shrink in a period? As we move from left to right across the periodic table, the atomic number increases, which means that the number of protons in the nucleus increases. Although the electrons also increase, they are contained in the same orbit. This increases the attraction of the nucleus and the electrons come closer to the nucleus, which shrinks the size of the atom. Why do some atoms lose electrons easily? Some atoms, such as metal elements, have only 1 or 2 electrons in their outer orbit. They easily lose these electrons to achieve a stable outer orbit. Furthermore, atoms in lower groups are larger, so their outer electrons are farther from the nucleus and the attraction on them is weaker, making them easier to eject. How many elements are in the periodic table? The modern periodic table currently contains 118 elements, some of which occur naturally while others are synthetically produced. These elements are arranged according to their atomic number. How is the periodic table organized? The periodic table is arranged based on the atomic number, electronic structure, and chemical properties of the elements. The table is divided into periods and groups. Elements that have similar properties are in the same group, while a period includes elements with similar orbitals. What is a period in the table? The horizontal row of the periodic table is called a period. The elements in each period have the same number of electron orbitals, but as the atomic number increases, their properties change. There are a total of 7 periods in the table. Where are metals located in the periodic table? Metals are mostly found in the left and middle of the periodic table. They include alkali metals, alkaline earth metals, and transition metals. There is a specific line in the table called a zigzag line, with most metals on the left and nonmetals on the right. What are the vertical columns in the periodic table called? The vertical columns of the periodic table are called groups. The chemical properties and outer orbital electrons (valence electrons) of the elements in each group are generally similar. There are a total of 18 groups in the table. How are the elements arranged in the periodic table? The elements are arranged in increasing order of their atomic number (i.e., number of protons) in the periodic table. This arrangement makes it easier to understand the electronic structure, chemical properties, and reactivity of the elements. This arrangement consists of periods (horizontal rows) and groups (vertical columns). What is a group in the periodic table? A group is a vertical column in the periodic table. The elements in each group have approximately the same number of outer electrons, so their chemical properties are similar. For example, all elements in group 1 have one electron and are very reactive metals. What is the periodic table? The periodic table is a systematic chart that lists all known chemical elements based on their atomic number, electronic structure, and properties. It helps scientists understand elements, their relationships, and predict chemical reactions. Why do some elements break periodic trends? Some elements break periodic trends because their electron configurations, orbital configurations, or atomic sizes differ from the general rules. For example, some elements behave oppositely to the expected trend due to electron pairing or subshell stability. This is why nitrogen has an electron acceptor near zero, even though it was expected to be higher. What element has the symbol Pm? The symbol Pm stands for promethium. It is a rare earth metal and part of the lanthanide series. This element is found naturally in very small amounts and is usually produced synthetically. Which element in group 1 reacts most vigorously with cold water? The most reactive element in Group 1, the alkali metals, is francium, but because it is very rare and unstable, rubidium and cesium also react violently with cold water. In practice, cesium has the highest observed intensity. What is the correct order of electron acceptability of N, O, S, and Cl? The order of electron affinities of these elements is: Cl > S > O > N Chlorine is the most reactive because it gains an electron to obtain a complete octet. Nitrogen does not accept electrons because of the stability of its half-filled orbital. Which alkali metal has the highest ionic mobility in water? Lithium (Li⁺) does not have the highest ionic mobility among the alkali metals, but larger ions such as cesium (Cs⁺) and rubidium (Rb⁺) show higher mobility in water due to their low hydration. However, the potassium ion (K⁺) shows the most effective ionic mobility in water. Why do some elements break periodic trends? Some elements break periodic trends because of their unique electronic configuration, orbital stability, or unusual way of filling subshells. For example, nitrogen has a very low electron affinity because its half-filled orbital is stable, which is affected by the addition of more electrons. Such exceptional elements behave differently from the general trends in the table. What element is the symbol for Pm? Pm stands for promethium. It is a rare earth metal, belonging to the lanthanide series. Promethium occurs naturally in very small quantities and is mostly produced synthetically. It is a radioactive element and is commonly used in research or special devices. Which element in Group 1 reacts most vigorously with cold water? Cesium is the element in Group 1 (alkali metals) that reacts most vigorously with cold water. When cesium is added to water, it can produce intense heat, hydrogen gas, and even an explosion. Although francium may theoretically be more reactive, it is very rare and unstable, so in practice cesium is the most active. What is the correct order of electron affinity for N, O, S, and Cl? The order of electron affinity for these elements is: Cl > S > O > N Chlorine has the highest electron affinity because it gains one electron to complete its octet. Sulfur is second because its ability to attract electrons to its nucleus is less than that of chlorine. Adding another electron to oxygen increases the electron repulsion. Nitrogen already has half-filled p orbitals, so it resists adding a new electron. Which alkali metal has the highest ionic mobility in water? The potassium ion (K⁺) has the highest ionic mobility in water. Although lithium is the lightest, its ion moves slowly in water due to its high hydration. Larger ions such as cesium have less hydration, but the size and hydration balance of K⁺ are such that it moves the fastest. Which element has zero valence? Noble gases (pure gases) such as helium, neon, argon, krypton, xenon, and radon are elements that have zero valence. Their outer orbitals are complete, so these elements generally do not react chemically and are considered stable. How can the chemical properties of an element be determined from its position in the periodic table? The position of an element in the periodic table can be used to determine its valence electrons, ionization energy, nature of reactivity, and metallic or non-metallic character. The group indicates how many electrons are in the outer orbital The period indicates how many electron shells (orbits) there are The ones on the left are usually metals, the ones on the right are non-metals, and the ones in the middle are semimetals. What is the order of ionization energies for an element? The order of ionization energy for an element is usually as follows: First ionization energy < Second ionization energy < Third ionization energy Because each time an electron is removed, the remaining electrons become more tightly bound to the nucleus. Sometimes, a big jump occurs when a stable octet is complete. What determines the metallic or nonmetallic character of elements? Whether an element is metallic or nonmetallic depends on its ionization energy, electronegativity, and atomic size. Metals have low ionization energies and large sizes, while nonmetals have high ionization energies and high electronegativity. What are the elements and special cases that are exceptions to the long-range trend? Some elements behave outside of periodic trends, such as: Nitrogen, which has a low electron acceptor despite not having a full orbital. Beryllium and the noble gases which have high ionization energies. The noble gases do not fit into the electron attraction order because their outer orbitals are full. These elements exhibit behavior outside of the normal trends due to the properties of their electron configuration or subshell stability.

Periodic Table Classification of – Elements Trends and Laws

Chemistry Basic Concepts – Atomic Structure, Bonding, Matter & Stoichiometry