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[Chemistry] Periodic Trends in Properties of Elements

Reading Time: 6 minutes

INTRODUCTION

Periodic trends are specific patterns in the properties of elements which keep on repeating after regular intervals in the periodic table.

Following are the periodic trends in some of the properties of elements;

ATOMIC RADII

WHAT IS ATOMIC RADIUS?

Atomic radius is half of the distance between the nuclei of the two bonded atoms.

MATHEMATICALLY

Atomic radius = d/2

Where,

D is the distance between the nuclei of two bonded atoms

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[Chemistry] Long Form of Periodic Table

Reading Time: 4 minutes

INTRODUCTION

the long form of periodic table is the present-day periodic table and is based upon the modern periodic law which establishes the atomic number of the elements as the basis for periodicity.

EXPLANATION

  • The significance of atomic number in the arrangement of elements in the modern periodic table lies in the fact that as electronic configuration is based upon atomic number, therefore the arrangement of elements in accordance with increasing atomic number displays the periodicity (repetition of properties after regular intervals) in the electronic configuration of the elements leading to periodicity in their properties.
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[Chemistry] Introduction to the periodic table

Reading Time: 3 minutes

INTRODUCTION

  • The periodic table is a list of elements arranged in the order of their increasing atomic (proton) numbers.

EXPLANATION

  • In nineteenth century, chemists devoted much of their efforts in attempts to arrange elements in a systematic manner.
  • These efforts resulted in discovery of periodic law.
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[Chemistry] Electronic Configuration

Reading Time: 6 minutes

INTRODUCTION

Electronic configuration is the distribution of electrons of an atom or molecule in orbitals.

REPRESENTATION OF ELECTRONIC CONFIGURATION

A detailed method for writing the electronic configuration of an atom that include information about the number of electrons in each subshell is shown below for hydrogen.

Another way of representing the electronic configuration of an atom is a diagram that places electrons in boxes.

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[Chemistry] Concept of Shell, Subshell and Orbital

Reading Time: 7 minutes

INRODUCTION

The atom consists of protons, neutrons and electrons. The protons and neutrons reside within the nucleus whereas electrons revolve around the nucleus in fixed orbits or shells. These shells are complex regions further consisting of subshells and orbitals.

SHELLS

  • Electrons are arranged in shells (energy levels) around the nucleus.
  • Energy levels are represented by the symbol n and are numbered according to how far they are from the nucleus.
  • The lowest energy level n=1 is closest to the nucleus, the energy level n=2 is further out and so on.
  • The different energy levels are designated by the alphabets K, L, M and so on.
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[Chemistry] Dual Nature Of Matter And Light

Reading Time: 4 minutes

BACKGROUND

  • Plank’s quantum theory tells us that light shows a dual character. It behaves both as a material particle and as a wave.
  • This idea was extended to matter in 1924 by Louis De-Broglie.

DE-BROGLEI’S CONCEPT

  • According to De-Broglie, all matter particles in motion have a dual character.
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[Chemistry] Structure of atoms

Reading Time: 5 minutes

INTRODUCTION

  • After the discovery of subatomic particles in the late 1800s and early 1900s, scientists began experimentation in order to provide a model that best explains the structure of an atom.
  • Rutherford’s model was most widely accepted but had some defects.
  • In order to cope with the defects in Rutherford’s model, Neil Bohr postulated his version of atomic model which is the most widely accepted model.
  • Neil Bohr based his model on Plank’s quantum theory and proposed a model which provides the best possible explanation for the structure of atom.
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[Chemistry] Stoichiometry

Reading Time: 5 minutes

INTRODUCTION

Stoichiometry is the branch of chemistry which tells us about the quantitative relationship between reactants and products in a balanced chemical equation.

ASSUMPTIONS

In order to perform stoichiometric calculations, the following assumptions must be taken into account

  1. All the reactants are completely converted into products
  2. No side reaction occurs

LAWS

While doing stoichiometric calculations, the following laws are obeyed

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[Chemistry] Mole

Reading Time: 4 minutes

INTRODUCTION

A mole of a substance is the amount that contains the same number of units (atoms, molecules or ions) as the number of carbon atoms in 12 grams of Carbon-12.

BACKGROUND

  • We know that atom is an extremely small particle.
  • The mass of an individual atom is a very small quantity and is not feasible for calculation.
  • It is impossible to weight individual atoms or even small groups of atoms directly.
  • Therefore, the concept of mole is used. One mole of a substance is the relative atomic/molecular mass expressed in grams.
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[Chemistry] Chemical Reaction

Reading Time: 3 minutes

INTRODUCTION

Chemical reaction is a process in which two or more substances interact with each other resulting in the formation of two or more new substances.

COMPONENTS OF CHEMICAL REACTION

A chemical reaction mainly consists of two components

  • Reactants
  • Products

REACTANTS

Reactants are the substances present at the start of a chemical reaction.

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