18-07-2013, 01:50 PM
STRUCTRE OF ATOM
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Charged particles in matter
Atoms have three types of sub atomic particles. They are electrons, protons and neutrons.
Electrons are negatively charged (e-), protons are positively charged (p+) and neutrons have no charge (n).
The mass of an electron is 1/2000 the mass of a hydrogen atom. The mass of a proton is equal to the mass of a hydrogen atom and is taken as 1 unit. The mass of a neutron is equal to the mass of a hydrogen atom and is and is taken as 1 unit.
Dalton’s Atomic Theory
1) All elements are composed of tiny indivisible particles called atoms
2) Atoms of the same element are identical. Atoms of any one element are different from those of any other element.
3) Atoms of different elements combine in simple whole-number ratios to form chemical compounds
4) In chemical reactions, atoms are combined, separated, or rearranged – but never changed into atoms of another element.
Charged particles in matter
Atoms have three types of sub atomic particles. They are electrons, protons and neutrons.
Electrons are negatively charged (e-), protons are positively charged (p+) and neutrons have no charge (n).
The mass of an electron is 1/2000 the mass of a hydrogen atom. The mass of a proton is equal to the mass of a hydrogen atom and is taken as 1 unit. The mass of a neutron is equal to the mass of a hydrogen atom and is and is taken as 1 unit.
Distribution of electrons in different shells
The distribution of electrons in the different shells was suggested by Bhor and Bury. The following are the rules for filling electrons in the different shells.
i) The maximum number of electrons in a shell is given by
the formula 2n2 where n is the number of the shell 1, 2, 3
etc.
First shell or K shell can have = 2n2 = 2 x 12 = 2x1x1 = 2 electrons
Second shell or L shell can have = 2n2 = 2 x 22 = 2x2x2 = 8 electrons
Third shell or M shell can have = 2n2 = 2 x 32 = 2x3x3 = 18 electrons
Fourth shell or N shell can have = 2n2 = 2 x 42 = 2x4x4 = 32 electrons
and so on.
ii) The maximum number of electrons that can be filled in
the outermost shell is 8.
iii) Electrons cannot be filled in a shell unless the inner
shells are filled.
Isotopes
Dalton was wrong about all elements of the same type being identical
Atoms of the same element can have different numbers of neutrons.
Thus, different mass numbers.
These are called isotopes.
[attachment=56690]
Charged particles in matter
Atoms have three types of sub atomic particles. They are electrons, protons and neutrons.
Electrons are negatively charged (e-), protons are positively charged (p+) and neutrons have no charge (n).
The mass of an electron is 1/2000 the mass of a hydrogen atom. The mass of a proton is equal to the mass of a hydrogen atom and is taken as 1 unit. The mass of a neutron is equal to the mass of a hydrogen atom and is and is taken as 1 unit.
Dalton’s Atomic Theory
1) All elements are composed of tiny indivisible particles called atoms
2) Atoms of the same element are identical. Atoms of any one element are different from those of any other element.
3) Atoms of different elements combine in simple whole-number ratios to form chemical compounds
4) In chemical reactions, atoms are combined, separated, or rearranged – but never changed into atoms of another element.
Charged particles in matter
Atoms have three types of sub atomic particles. They are electrons, protons and neutrons.
Electrons are negatively charged (e-), protons are positively charged (p+) and neutrons have no charge (n).
The mass of an electron is 1/2000 the mass of a hydrogen atom. The mass of a proton is equal to the mass of a hydrogen atom and is taken as 1 unit. The mass of a neutron is equal to the mass of a hydrogen atom and is and is taken as 1 unit.
Distribution of electrons in different shells
The distribution of electrons in the different shells was suggested by Bhor and Bury. The following are the rules for filling electrons in the different shells.
i) The maximum number of electrons in a shell is given by
the formula 2n2 where n is the number of the shell 1, 2, 3
etc.
First shell or K shell can have = 2n2 = 2 x 12 = 2x1x1 = 2 electrons
Second shell or L shell can have = 2n2 = 2 x 22 = 2x2x2 = 8 electrons
Third shell or M shell can have = 2n2 = 2 x 32 = 2x3x3 = 18 electrons
Fourth shell or N shell can have = 2n2 = 2 x 42 = 2x4x4 = 32 electrons
and so on.
ii) The maximum number of electrons that can be filled in
the outermost shell is 8.
iii) Electrons cannot be filled in a shell unless the inner
shells are filled.
Isotopes
Dalton was wrong about all elements of the same type being identical
Atoms of the same element can have different numbers of neutrons.
Thus, different mass numbers.
These are called isotopes.