WHAT IS A COMPOUND?
A compound is like a team made up of different players (atoms). These players join together to form a new substance with its own special characteristics. In other words, a compound is a substance made when two or more different kinds of atoms stick together.
How Compounds Form:
Atoms: Atoms are tiny building blocks. Each element, like oxygen or hydrogen, has its own unique type of atom.
Bonding: Atoms can stick together through something called bonding. It's like atoms holding hands to form a compound.
Ionic Bonding: Sometimes, atoms exchange electrons. This creates charged particles (ions) that are attracted to each other, like magnets. Table salt (NaCl) is an example.
Covalent Bonding: Other times, atoms share electrons, like best friends sharing snacks. Water (H2O) is an example of a compound formed through covalent bonding.
Chemical Formulas:
A chemical formula is like a recipe that tells us what elements are in a compound and how many of each. It's like writing down the types and amounts of ingredients needed for a dish.
Water Example: The chemical formula for water is H2O. It tells us there are two hydrogen atoms (H) and one oxygen atom (O) in each water molecule.
Molecules:
A molecule is a group of atoms stuck together. Compounds are made of molecules.
Oxygen Example: Oxygen gas (O2) is a molecule made of two oxygen atoms bonded together.
COMPOUND DEFINITION
A compounds is a pure substance made up of two or more elements chemically combined with one another in a fixed proportion by mass.
It may be noted that a pure compound, whatever its source always contains definite or constant proportions of elements by mass. For example, water is composed of two elements: hydrogen and oxygen. Irrespective of its source, all samples of pure water contain these elements combined together in the ratio of 1 : 8 by mass. The compound
can be formed by different chemical methods from their constituent elements. Alternately, it can also be decomposed into their constituent elements by different chemical methods.
For example, water is a compound made up of two elements, hydrogen and oxygen. It can be formed by the chemical combination of hydrogen and oxygen in a fixed proportion of
1 : 8 by mass.
[Atomic masses : H = 1, O = 16, so that in water, H2O, H2: O = 2 : 16 = 1 : 8]
Conversely, water can also be broken down into the elements hydrogen and oxygen by passing electric current though it.
Water Hydrogen + Oxygen
It may be noted that during decomposition, hydrogen and oxygen are also obtained in a fixed proportion of 1: 8 by mass.
Thus, a chemical compound contains the same elements in a fixed proportion by mass.
The common examples of compounds are: water, common salt and carbon dioxide.
A compound is represented by a formula which indicates the elements present in it and the relative number of atoms of each element. Water is represented by the formula H2O because it contains two hydrogen atoms (as subscript of hydrogen is 2) and one oxygen atom (as subscript of oxygen is 1)
CHARACTERISTICS OF A COMPOUND:
We already studied that A compound is a substance composed of two or more elements that are chemically combined in fixed proportions.
Here are some key characteristics of compounds:
Chemical Composition:
Compounds are formed when atoms of different elements chemically combine in fixed ratios to create a new substance.
The ratio of the constituent elements in a compound is always constant.
Chemical Bonding:
Compounds are held together by chemical bonds. These bonds can be covalent (shared electrons) or ionic (transfer of electrons).
The type of bonding influences the properties of the compound.
Physical State:
Compounds can exist in different physical states: solid, liquid, or gas, depending on the temperature and pressure conditions.
Properties:
Compounds have unique properties that differ from the properties of their constituent elements.
For example, sodium (a metal) and chlorine (a non-metal) are both dangerous in their elemental forms, but when combined, they form sodium chloride (table salt), which is safe for consumption.
Melting and Boiling Points:
Compounds have specific melting and boiling points, which are different from those of the individual elements.
These points depend on the strength and type of bonds within the compound.
Energy Changes:
The formation of a compound involves an exchange or sharing of electrons, leading to energy changes.
Energy is either released (exothermic) or absorbed (endothermic) during the formation of a compound.
Chemical Reactions:
Compounds participate in chemical reactions, where they can break down into simpler substances or combine with other substances to form new compounds.
Formula:
Compounds are represented by chemical formulas that indicate the types and ratios of atoms present in the compound.
For example, water is represented by the chemical formula H2O, indicating two hydrogen atoms and one oxygen atom.
Electric Conductivity:
Compounds can be classified into two main types based on their ability to conduct electricity: ionic compounds typically conduct electricity when dissolved in water, while covalent compounds generally do not.
Solubility:
Compounds may exhibit different solubilities in various solvents. Some compounds dissolve easily in water, while others may be soluble in organic solvents.
some compounds are given below
Compounds Formula
Water H2O
Carbon dioxide CO2
Common salt (Sodium chloride) NaCl
Sugar C12H22O11
Copper sulphate CuSO4
Nitric acid HNO3
Hydrochloric acid HCl
Marble (Calcium carbonate) CaCO3
Sand SiO2
Sulphuric acid H2SO4
Bleaching powder CaOCl2
Lead nitrate Pb(NO3)2
Methane CH4
Lime water Ca(OH)2