I want to know the concept of atoms and molecules of 9th class
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hlo mate... can you say which part of atoms and molecules do you want to learn
rijul96:
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Atoms and Molecules:
Atoms are also known as building blocks of all matter. This has been discovered that atoms are also divisible and can be further divided into electrons, protons, and neutrons, which further can be subdivided into quarks. In short, everything you see around yourself is made of atoms, even you yourself are made up of atoms. This sounds interesting, isn’t it? So, now you might be thinking about the size of an atom as I said they are too small rather smallest that their radii are measured in nanometres (10-9 meter). Atoms mostly can’t exist independently, they exist in the form of molecules or ions. These molecules aggregate in large numbers to form matter. So, a molecule is a group of two or more atoms chemically bonded together. In this article, find everything you need to know about atoms and molecules!
Laws of Chemical Combination:
Law of Conservation of Mass:
This law states that during a chemical reaction, the total mass of products will be equal to the total mass of reactants i.e. mass can neither be created nor be destroyed.
Eg: A(Reactant) + B(Reactant) = AB(Product)
mass of A + mass of B = mass of AB
Dalton’s Atomic Theory:
According to Dalton’s atomic theory, all matter, whether an element, a compound or a mixture is composed of small particles called
atoms.
The postulates of his theory can be stated as follows:
(i) All matter is made of very tiny particles called atoms.
(ii) Atoms are indivisible particles, which cannot be created or destroyed in a chemical reaction.
(iii) Atoms of a given element are identical in mass and chemical properties.
(iv) Atoms of different elements have different masses and chemical properties.
(v) Atoms combine in the ratio of small whole numbers to form compounds.
(vi) The relative number and kinds of atoms are constant in a given compound.
proposed by Dalton
Nowadays, IUPAC (International Union of Pure and Applied Chemistry) approves names of elements. These are used for representing both atoms and molecules.
The first letter of a symbol is always written as a capital letter (uppercase) and the second letter as a small letter (lowercase). For example: (i) hydrogen, H (ii) aluminum, Al and not AL
Symbols of some elements are formed from the first letter of the name and a letter, appearing later in the name. For example: (i) chlorine, Cl (ii) zinc, Zn
Some other symbols have been taken from the name of elements from Latin or Greek. For example: (i) Potassium, K from Kalium (ii) Sodium, Na from Natrium
Some Important Terminology:
Atomicity:
The number of atoms constituting a Molecule is known as its atomicity
Atomic Mass:
The mass of an atom of an element is called its atomic mass. It is represented in the atomic mass unit (u). The atomic mass unit is defined as the quantity of mass equal to 1/12 of the mass of an atom of carbon-12.
Molecular Mass:
It is defined as the sum of the atomic mass of all elements present in a molecule.
Valency:
It is defined as the combining capacity of an element. Every atom in order to attain stability either gain, lose or share electrons.
The outermost shell is called valence shell and the number of electrons in the valence shell determines the valency.
1. Metals have the tendency to donate electrons so their valency is positive i.e. If an atom consists of 1, 2 or 3 electrons in its valence shell then its valency is 1, 2 or 3 respectively. Eg: Sodium has a valency of +1.
2. Non- Metals have the tendency to gain electrons so their valency is negative i.e. If an atom consists of 5, 6 or 7 electrons in its valence shell then its valency is -3, -2 or -1 respectively. Eg: Chlorine has a valency of -1.
Formula mass:
It is the sum of the atomic masses of all atoms in a formula unit of a compound. The constituent particles are ions.
Chemical Formulae:
The chemical formula of a compound is a symbolic representation of its composition. There are some rules which must be followed while writing chemical formula of a compound.
Rules:
(i) The valencies or charges on the ion must balance.
(ii) A metal and non-metal compound should show the name or symbols of the metal first.
e.g. Na+ Cl– → NaCl
(iii) If a compound consists of polyatomic ions, the ion is enclosed in a bracket before writing the number to indicate the ratio
e.g. [SO4]2– → polyatomic radical
H1+ SO42– → H2SO4.
Mole Concept:
Mole: It is used to express the quantity of a substance. 1 mole is defined as the amount of substance which contains 6.022 x 1023 units of a particle.
1 mole = 6.022 x 1023 units ( Avogadro’s number)
Molar mass: The mass of 1 mole of a substance is known as molar mass. It is expressed in grams.
Number of moles can be calculated using:
n (no. of moles) = Given mass/ Molar mass = number of particles/ Avogadro’s number
This was all about atoms and molecules according to the syllabus of class 9th. Stay tuned for more such articles.
MARK ME BRAINLIEST IF IT HELPS
Atoms and Molecules:
Atoms are also known as building blocks of all matter. This has been discovered that atoms are also divisible and can be further divided into electrons, protons, and neutrons, which further can be subdivided into quarks. In short, everything you see around yourself is made of atoms, even you yourself are made up of atoms. This sounds interesting, isn’t it? So, now you might be thinking about the size of an atom as I said they are too small rather smallest that their radii are measured in nanometres (10-9 meter). Atoms mostly can’t exist independently, they exist in the form of molecules or ions. These molecules aggregate in large numbers to form matter. So, a molecule is a group of two or more atoms chemically bonded together. In this article, find everything you need to know about atoms and molecules!
Laws of Chemical Combination:
Law of Conservation of Mass:
This law states that during a chemical reaction, the total mass of products will be equal to the total mass of reactants i.e. mass can neither be created nor be destroyed.
Eg: A(Reactant) + B(Reactant) = AB(Product)
mass of A + mass of B = mass of AB
Dalton’s Atomic Theory:
According to Dalton’s atomic theory, all matter, whether an element, a compound or a mixture is composed of small particles called
atoms.
The postulates of his theory can be stated as follows:
(i) All matter is made of very tiny particles called atoms.
(ii) Atoms are indivisible particles, which cannot be created or destroyed in a chemical reaction.
(iii) Atoms of a given element are identical in mass and chemical properties.
(iv) Atoms of different elements have different masses and chemical properties.
(v) Atoms combine in the ratio of small whole numbers to form compounds.
(vi) The relative number and kinds of atoms are constant in a given compound.
proposed by Dalton
Nowadays, IUPAC (International Union of Pure and Applied Chemistry) approves names of elements. These are used for representing both atoms and molecules.
The first letter of a symbol is always written as a capital letter (uppercase) and the second letter as a small letter (lowercase). For example: (i) hydrogen, H (ii) aluminum, Al and not AL
Symbols of some elements are formed from the first letter of the name and a letter, appearing later in the name. For example: (i) chlorine, Cl (ii) zinc, Zn
Some other symbols have been taken from the name of elements from Latin or Greek. For example: (i) Potassium, K from Kalium (ii) Sodium, Na from Natrium
Some Important Terminology:
Atomicity:
The number of atoms constituting a Molecule is known as its atomicity
Atomic Mass:
The mass of an atom of an element is called its atomic mass. It is represented in the atomic mass unit (u). The atomic mass unit is defined as the quantity of mass equal to 1/12 of the mass of an atom of carbon-12.
Molecular Mass:
It is defined as the sum of the atomic mass of all elements present in a molecule.
Valency:
It is defined as the combining capacity of an element. Every atom in order to attain stability either gain, lose or share electrons.
The outermost shell is called valence shell and the number of electrons in the valence shell determines the valency.
1. Metals have the tendency to donate electrons so their valency is positive i.e. If an atom consists of 1, 2 or 3 electrons in its valence shell then its valency is 1, 2 or 3 respectively. Eg: Sodium has a valency of +1.
2. Non- Metals have the tendency to gain electrons so their valency is negative i.e. If an atom consists of 5, 6 or 7 electrons in its valence shell then its valency is -3, -2 or -1 respectively. Eg: Chlorine has a valency of -1.
Formula mass:
It is the sum of the atomic masses of all atoms in a formula unit of a compound. The constituent particles are ions.
Chemical Formulae:
The chemical formula of a compound is a symbolic representation of its composition. There are some rules which must be followed while writing chemical formula of a compound.
Rules:
(i) The valencies or charges on the ion must balance.
(ii) A metal and non-metal compound should show the name or symbols of the metal first.
e.g. Na+ Cl– → NaCl
(iii) If a compound consists of polyatomic ions, the ion is enclosed in a bracket before writing the number to indicate the ratio
e.g. [SO4]2– → polyatomic radical
H1+ SO42– → H2SO4.
Mole Concept:
Mole: It is used to express the quantity of a substance. 1 mole is defined as the amount of substance which contains 6.022 x 1023 units of a particle.
1 mole = 6.022 x 1023 units ( Avogadro’s number)
Molar mass: The mass of 1 mole of a substance is known as molar mass. It is expressed in grams.
Number of moles can be calculated using:
n (no. of moles) = Given mass/ Molar mass = number of particles/ Avogadro’s number
This was all about atoms and molecules according to the syllabus of class 9th. Stay tuned for more such articles.
MARK ME BRAINLIEST IF IT HELPS
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