Compounds and Elements

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Introduction to compounds and elements

Compounds:

The compound is defined as a pure substance containing two or more elements which are combined together in a fixed proportion by mass.

Elements:

An element is the simplest or basic form of a pure substance which cannot be broken into anything simpler than it by physical or chemical methods.  The pure substance which is made up of one kind of atoms only.  The common examples of elements are hydrogen, carbon, , sulphur, gold etc.

Types of Elements

Elements are further classified into three types.

  1. Metals
  2. Non-metal
  3. Semi-metals

Metals

  • Metals are solids at room temperature.
  • Metals are generally quite hard.
  • Good conductors.
  • Naturally Malleable.
  • Naturally Ductile.
  • Metals have generally high melting and boiling points.

Non-metals

  • Non-metals are either gases or solids at room temperature.
  • Non-metal varies in colour.  Solids have generally dull surfaces.
  • Non-metals are mostly poor conductor of heat and electricity.
  • Most of the non-metals are quite soft and have smaller densities than metals.
  • Non-metal are non-malleable and non-ductile in nature.
  • Non-metals are also not sonorous in nature.
  • As compared to the metals, the non-metals have very low melting and boiling points.

Semi-metals

There are few elements which possess the characteristics of both metals and non-metals.  These are actually border-line elements and are known as semi-metals.  Semi-metals are also called as metalloids.  A few common examples are:  Arsenic, Antimony and Bismuth.

Types of elements based on physical states:

Based on physical states, the elements have been classified as solids, liquids and gases.

Solid elements: Most of the elements are solids at room temperature.  For example, copper, silver, gold, potassium, carbon (diamond, graphite), iodine, phosphorous etc.

Liquid elements: Only mercury and bromine exist as liquid at room temperature.  Gallium and cesium become liquids at a temperature 302 K and 303 K respectively.  These are slightly higher than the room temperature (298 K).

Gaseous elements: Eleven elements exist in the gaseous state at room temperature.  These are hydrogen, oxygen, nitrogen, fluorine, chlorine, helium, neon, argon, krypton, xenon and radon.

Types of Compounds

A compound is also a pure substance like elements. But it represents a combination of two or more elements which are combined chemically.

Types of compounds

The compounds have been classified into two types

  • Organic compounds
  • Inorganic compounds

Organic compounds

Organic compounds are the compounds which are obtained from living beings (plant and animal).  It has been found that all the organic compounds contain carbon as their essential constituent.  The organic compounds are quite often known as carbon compounds.

Examples:  Methane, ethane, propane, alcohol, etc.

Inorganic compounds

Inorganic compounds have mostly obtained from non-living sources such as rocks and minerals.

Example:  Salt, marble, washing soda, baking soda, etc.

Characteristics of compounds:

  • A pure compound is composed of the same elements combined in a fixed ratio by mass.
  • A pure compound is homogeneous in nature.
  • A chemical compound is formed as a result of chemical reaction between the constituent elements.
  • Properties of the compound are altogether different from the elements from which it is formed.
  • Constituents of a chemical compound cannot be separated mechanically.