Grade 9
  1. Matter and its nature  1.1. Introduction to matter  1.2. Physical and chemical properties of matter  1.3. States of matter  1.3.1. Solid state  1.3.2. Fluid state  1.3.3. Gaseous state  1.3.4. Plasma and Bose–Einstein condensate  1.4. Changes in the states of matter  1.4.1. Melting and freezing  1.4.2. Evaporation and Condensation  1.4.3. Sublimation and deposition  1.5. Classification of matter  1.6. Elements, Compounds, and Mixtures  1.7. Pure substances and impurities  1.8. Separation Techniques  1.8.1. Filtration  1.8.2. Distillation  1.8.3. Crystallization  1.8.4. Chromatography  1.8.5. Centrifugation  1.8.6. Sublimation  1.8.7. Decantation and sedimentation
  2. Atomic Structure  2.1. Discovery of atoms  2.2. Dalton's atomic theory  2.3. Structure of the atom  2.4. Subatomic particles  2.5. Atomic number and mass number  2.6. Isotopes and Isobars  2.7. Electronic configuration  2.8. Bohr's atomic model  2.9. Modern Atomic Model (Quantum Mechanical Model - Introduction)  2.10. Valency and chemical bonding
  3. C hemical reactions and equations  3.1. Introduction to Chemical Reactions  3.2. Chemical Equation Formulation  3.3. Balancing Chemical Equations  3.4. Types of Chemical Reactions  3.4.1. Combination Reactions  3.4.2. Decomposition reactions  3.4.3. Displacement reactions  3.4.4. Double displacement reactions  3.4.5. Redox reactions  3.4.6. Endothermic and Exothermic Reactions  3.5. Effects of chemical reactions  3.6. Energy Changes in Chemical Reactions  3.7. Catalysts and their role in reactions
  4. Periodic table and periodicity  4.1. History of Periodic Classification  4.2. Mendeleev's periodic table  4.3. Modern Periodic Table  4.4. Periods and groups in the periodic table and periodicity  4.5. Trends in the Periodic Table  4.5.1. Atomic size  4.5.2. Ionization Energy  4.5.3. Electron affinity  4.5.4. Electronegativity  4.5.5. Metallic and Non-Metallic Properties  4.6. Noble gases and their properties
  5. Chemical bond  5.1. Introduction to Chemical Bonding  5.2. Types of chemical bonds  5.2.1. Ionic bond  5.2.2. Covalent bond  5.2.3. Metallic bond  5.2.4. Hydrogen bonding  5.2.5. Van der Waals force  5.3. Properties of Ionic and Covalent Compounds  5.4. Molecular Structure and Geometry (VSEPR Theory - Basics)
  6. Acids, Bases and Salts  6.1. Introduction to Acids and Bases  6.2. Properties of Acids  6.3. Properties of bases  6.4. pH scale and its importance  6.5. Indicators and their uses  6.6. Neutralization reactions  6.7. Strength of Acids and Bases (Strong vs. Weak)  6.8. Preparation of salts  6.9. Uses of acids, bases and salts in daily life
  7. Metals and Nonmetals  7.1. Physical Properties of Metals  7.2. Physical Properties of Nonmetals  7.3. Chemical properties of metals  7.4. Chemical Properties of Nonmetals  7.5. Reactivity Series of Metals  7.6. Extraction of metals  7.7. Corrosion and its prevention  7.8. uses of metals and nonmetals
  8. Carbon and its compounds  8.1. Introduction to Carbon  8.2. Allotropes of carbon (diamond, graphite, fullerene)  8.3. Hydrocarbons  8.3.1. Hydrocarbons  8.3.2. Alkene  8.3.3. Alkynes  8.4. Functional groups in organic chemistry  8.5. Isomerism in organic compounds  8.6. Alcohols and Carboxylic Acids  8.7. Soaps and detergents  8.8. Polymers (Introduction to Natural and Synthetic Polymers)
  9. Solutions and Mixtures  9.1. Types of mixtures  9.2. Homogeneous and Heterogeneous Mixtures  9.3. Concentration of solutions  9.4. Solubility and factors affecting solubility  9.5. Suspensions and Colloids  9.6. Saturated, unsaturated and supersaturated solutions
  10. Air and atmosphere  10.1. Composition of air  10.2. Role of gases in the atmosphere  10.4. Acid rain and its effects  10.5. Greenhouse effect and global warming  10.6. Ozone layer and its depletion  10.7. Air pollution control measures
  11. Water and its importance  11.1. Composition and properties of water  11.2. Hardness of water (temporary and permanent hardness)  11.3. Causes of water pollution  11.4. Effects of Water Pollution  11.5. Water purification methods (filtration, boiling, chlorination)
  12. Industrial Chemistry  12.1. Introduction to Industrial Chemistry  12.2. Important industrial chemicals (sulfuric acid, ammonia, sodium hydroxide)  12.3. Chemical processes in industry  12.4. Uses of Industrial Chemistry in Daily Life  12.5. Environmental impact of industrial chemical processes

Grade 9 ↓


Periodic table and periodicity


The periodic table is a systematic arrangement of all known chemical elements. It is an important tool in the field of chemistry, allowing scientists and students to understand the properties and interactions of the elements at a glance. This document will explain the structure, importance, and periodicity of the periodic table, providing as much clarity as possible.

History of the periodic table

The development of the periodic table was initiated by Russian chemist Dmitry Mendeleev in 1869. Mendeleev arranged the elements in order of increasing atomic mass and observed that elements with similar properties occurred at regular intervals, forming a periodic pattern.

Structure of the periodic table

The periodic table is the tabular arrangement of elements in rows and columns. Let us see its structure in detail:

Lines: Period

The rows of the periodic table are called periods. There are seven periods in the table. As you move from left to right in a period, the atomic number of each element increases by one. This arrangement shows the sequential filling of electron shells in atoms.

1 H He 2 Li Be BCNOF Ne 3 Na Mg Al Si PS Cl Ar 4 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr 5 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe 6 Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn 7 Fr Ra Ac Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og Lanthanides: Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Actinides: Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr

For example, period 1 contains hydrogen (H) and helium (He). Going from left to right in any period, we find elements that become progressively heavier.

Column: Group

The columns of the periodic table are called groups or families. Each group contains elements with similar chemical properties. This similarity is due to the elements having the same number of electrons in their outermost shells.

There are 18 groups in the periodic table, and they are often numbered at the top of each column. Some important groups include:

  • Group 1: Alkali metals (e.g., lithium, sodium)
  • Group 2: Alkaline earth metals (e.g., beryllium, magnesium)
  • Group 17: Halogens (e.g., fluorine, chlorine)
  • Group 18: Noble gases (e.g., helium, neon)

Periodicity and chemical properties

Periodicity refers to trends and recurring variations in element properties based on their position in the periodic table. This concept helps in predicting the chemical behaviour of an element.

Atomic radius

The atomic radius is the distance from the nucleus of an atom to the outermost electron. Within a period, the atomic radius decreases from left to right because the increasing number of protons pulls the electron cloud closer to the nucleus.

For example, in period 3:

  • The atomic radius of sodium (Na) is larger than that of chlorine (Cl).
NaMgAlSiCl

Ionization energy

Ionization energy is the energy required to remove an electron from an atom in the gaseous state. It increases across a period because a stronger nuclear charge holds the electrons more tightly.

Consider period 2, where the ionization energy of boron (B) is less than that of neon (Ne).

Electronegativity

Electronegativity measures the ability of an atom to attract shared electrons in a chemical bond. It generally increases across a period and decreases down a group.

For example, fluorine (F) is more electronegative than lithium (Li).

Trends in groups

Just as trends occur over different periods of time, trends also occur in groups:

Metal character

Metallic character refers to the ability of an element to lose electrons and form positive ions (cations). It increases down the group and decreases across a period.

For example, in group 1, francium (Fr) is more metallic than lithium (Li).

Reactivity

The reactivity of metals increases as we move down a group. In contrast, the reactivity of non-metals decreases as we move down a group.

Alkali metals like sodium (Na) and potassium (K) are highly reactive.

Importance of periodic table

The periodic table is important for understanding the interactions of elements in chemical reactions. It helps chemists predict the behavior of elements, create new materials, and explore chemical bonds.

Prediction of chemical reactions

By understanding the properties and tendencies of elements, chemists can predict how elements will react. For example, knowing that the elements of group 17 are highly reactive allows predictions of vigorous reactions with elements of group 1.

New material design

Researchers use this table to discover new alloys and compounds, and to study how different elements combine to form materials useful in technology, medicine, and everyday life.

The periodic table remains a fundamental tool, not only revealing the minute details of atomic structure but also providing insight into the profound complexity of the chemical world.


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Periodic table and periodicity

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