ChemistryClassification of Elements and Periodicity in Properties

Classification of Elements and Periodicity in Properties

Why Do We Need to Classify Elements? ; Example

The reason we need to classify elements is because it helps us to understand and organize them. It also makes it easier to find information about them. For example, if we want to know what elements are in Group 2 of the periodic table, we can easily find that information because all of the elements in Group 2 are classified together.

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    Genesis of Periodic Classification of Elements

     

    The periodic table is a tabular display of the chemical elements, ordered by atomic number, electron configuration, and recurring chemical properties. The modern form of the periodic table was developed by Russian chemist Dmitry Mendeleev in 1869.

    The elements are displayed in columns (called groups) and rows (called periods), with the elements in each row having the same number of electron shells. The table is divided into blocks, which are separated by areas of low electron density.

    The periodic table is based on the electronic structure of the elements, which determines their chemical properties. The periodic table can be used to predict the properties of unknown elements, and it has been used to develop new theories of chemical bonding.

    Modern Periodic Law and the Present Form of the Periodic Table

    The modern periodic law states that when elements are arranged by their atomic number, they fall into certain recurring patterns or periods. The present form of the periodic table arranges elements by atomic number and groups them into periods and families. The table is divided into seven periods, and each period contains 18 groups (or columns). The groups are numbered 1-18, and each group contains a certain number of elements. The elements in a group have similar chemical and physical properties.

    Nomenclature of Elements with Atomic Number > 100

    According to the IUPAC (International Union of Pure and Applied Chemistry) standard, elements with atomic numbers greater than 100 are named with the prefix “un-” followed by the element’s atomic number. For example, element 118 is called “ununoctium.”

    Electronic Configuration of Elements and the Periodic Table

    The electronic configuration of an atom is the arrangement of electrons in shells and subshells. The Periodic Table is a chart of the elements that arranges them in order of increasing atomic number. The element’s position on the table is determined by the number of protons in the nucleus of the atom.

    The electronic configuration of an atom can be determined by the number of protons in the nucleus and the number of electrons in the atom. The number of protons in the nucleus is called the atomic number. The number of electrons in the atom is equal to the number of protons in the nucleus plus the number of neutrons in the nucleus.

    The electronic configuration of an atom can also be determined by the number of shells and subshells. The number of shells is determined by the number of protons in the nucleus. The number of subshells is determined by the number of electrons in the atom.

    The electronic configuration of an atom can also be determined by the number of electrons in the highest occupied shell. The number of electrons in the highest occupied shell is called the valence electrons.

    The electronic configuration of an atom can also be determined by the type of element. The type of element is determined by the number of protons in the nucleus and the number of electrons in the atom.

    The electronic configuration of an atom can also be determined by the type of bond. The type of bond is determined by the number of electrons in

    Types of Elements: s, p, d, f – Blocks

    There are four types of block elements in the periodic table: s-block, p-block, d-block, and f-block.

    The s-block elements are located in the leftmost column of the periodic table and include the alkali metals and alkaline earth metals.

    The p-block elements are located in the second column of the periodic table and include the halogens and noble gases.

    The d-block elements are located in the third and fourth columns of the periodic table and include the transition metals and inner transition metals.

    The f-block elements are located in the fifth and sixth columns of the periodic table and include the lanthanides and actinides.

    Classification of the Elements

    The elements are classified into three categories: metals, nonmetals, and metalloids.

    Metals are shiny and have a high melting point. They are good conductors of heat and electricity. Examples of metals are gold, silver, and copper.

    Nonmetals are dull and have a low melting point. They are poor conductors of heat and electricity. Examples of nonmetals are carbon, oxygen, and nitrogen.

    Metalloids have some properties of metals and some properties of nonmetals. They are poor conductors of heat and electricity. Examples of metalloids are silicon and germanium.

    Periodic Trends in Properties of Elements

    The physical and chemical properties of elements vary periodically as you move from left to right across the periodic table. This is because the atomic number of an element (the number of protons in the nucleus) increases as you move from left to right. As the atomic number increases, the atom becomes increasingly stable because the positive charges in the nucleus are balanced by the negative charges of the electrons in the electron cloud.

    The elements in the left column (Group 1) have one electron in their outermost energy level. This electron is easily lost, so these elements are very reactive. The elements in the right column (Group 7) have seven electrons in their outermost energy level. This makes them very stable and unreactive.

    The elements in the middle of the table have different numbers of electrons in their outermost energy level, and this affects their chemical reactivity.

    Atomic Radius

    The atomic radius is the distance from the center of the atom to the outermost electron.

    The atomic radius of an element can be found on the periodic table. The atomic radius of an element increases as you go down the column and decreases as you go up the column.

    Ionization Energy

    The ionization energy is the energy required to remove an electron from an atom. It is a measure of the strength of the atom’s electron-binding forces. The higher the ionization energy, the stronger the atom’s electron-binding forces.

    The ionization energy of an atom can be increased by increasing the strength of the atom’s electron-binding forces. This can be done by increasing the atom’s nuclear charge or by increasing the atom’s electron shielding.

    The ionization energy of an atom can also be increased by decreasing the size of the atom. This can be done by increasing the atom’s atomic radius.

    The ionization energy of an atom can also be increased by increasing the temperature of the atom. This can be done by increasing the atom’s kinetic energy.

    Electron Affinity

    The electron affinity of an atom is the energy released when an electron is added to a neutral atom to form a negative ion.

    Electronegativity

    The electronegativity of an atom is a measure of how strongly it attracts electrons to itself. The higher the electronegativity of an atom, the more it will pull electrons away from other atoms.

    The electronegativity of an atom is determined by its electron configuration. The most electronegative elements are those with the most tightly bound electrons, such as fluorine, oxygen, and nitrogen.

    Valence Electrons

    Valence electrons are the electrons in an atom that are available to form chemical bonds. The number of valence electrons in an atom can vary, depending on the element. The most common valence electrons are the outermost electrons in an atom.

    Valency

    The valency of an atom is the number of electrons it has available to form covalent bonds.

    Elements of 2nd Period

    This period contains the following elements:

    – A review of the material from the previous period.

    – A new topic or concept.

    – Practice problems.

    – A quiz or test.

    Li

    Be, B ,C

    N

    O

    F

    Ne

    Metallic Character of the Elements

    Every atom consists of a nucleus and one or more electrons. The nucleus contains protons and neutrons. The number of protons in an atom determines what element it is. For example, an atom with six protons is carbon and an atom with eight protons is oxygen.

    The number of protons in an atom also determines how much of an element it is. For example, an atom with six protons is 100% carbon, while an atom with eight protons is only 50% oxygen.

    The electrons orbit the nucleus in shells. The number of electrons in an atom determines how reactive it is. For example, an atom with one electron in its outer shell is very reactive because it wants to fill its shell.

    The electron configuration of an atom can be changed by adding or removing electrons. When an atom loses electrons, it becomes a positive ion. When an atom gains electrons, it becomes a negative ion.

    Non – Metallic Character of the Elements

    Nonmetallic elements are those that do not have a metallic character. They are found on the right-most side of the periodic table and are typically gases, nonmetallic solids, or liquids. Nonmetallic elements are usually poor conductors of electricity and heat.

    Reactivity of Elements

    The reactivity of an element refers to how likely it is to form a chemical bond with another atom. The most reactive elements are the alkali metals, which are found in Group 1 of the periodic table. These elements are so reactive that they must be stored in oil to prevent them from reacting with the air. The least reactive elements are the noble gases, which are found in Group 18 of the periodic table. These elements are so unreactive that they can be stored in a vacuum.

    Melting and Boiling Points of Elements

    The melting and boiling points of elements are important to know because they are related to the strength of chemical bonds. The higher the melting and boiling points, the stronger the chemical bond.

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