ATOM – smallest unit of life

INDEX

• 1.INTRODUCTION

• 2. PARTS OF AN ATOM

• 2.1 NEUTRON

• 2.2 PROTON

• 2.3 ELECTRON

• 3 NUCLEUS

• 4. CHARGE OF AN ATOM

• 5. SHAPE, SIZE AND MASS OF AN ATOM

• 6. STABILITY

• 7. FISSION AND FUSION OF AN ATOM

INTRODUCTION

Atom is smallest unit of matter. Every state of matter contain atoms and atom contain electrons, protons and neutrons.

According to some theories the protons, electrons and neutrons are made up by small particles called quarks. And quarks are supposed to be smallest particles

NEUTRON

neutron is a part of nucleus and have no charge so it is neutral.

Only hydrogen atom not have any neutron.

PROTON

proton is a positive charge particle stable in nucleus with neutrons

ELECTRON

electron is a negative charge particle revolve around the nucleus. the electron would not be stable in nucleus because it does not emit enough energy to be a part of nucleus.

NUCLEUS

Protons and neutrons are in stable state in nucleus and the electrons revolve around the nucleus.

Neutrons and protons together called nucleons

The number of proton is called atomic number and the sum of number of proton, neutrons called mass number.

CHARGE OF AN ATOM

Protons have positive charge and electrons have negative charge so electrons attracted toward nucleus by electromagnetic force while neutrons are neutral.so that electrons revolve around the nucleus.

An atom is neutral in charge because the number of protons and electrons in atom are equal.

If the number of electrons are greater then protons, the atom have negative charge or if the electrons are removed from atom, the atom is positively charged. such charged atoms are called ions.

SHAPE, SIZE & MASS OF AN ATOM

The approximate diameter of atom is 1 x 10^-10m to 5 x 10^-10m and aproximate diameter of neucleus of atom is 1 x 10^-15m.

the shape of an atom is not perfectly sphere but is ellipsoid. mostly atom’s shape atom’s shape is prolate or oblate.

Mass of proton = 1.67262 × 10 −27 kg

mass of electron = 9.11 x 10 -28 kg

mass of neutron = 1.674×10−27 kg

About 99.9% mass of an atom contains in nucleus.

STABILITY OF AN ATOM

Mostly stable atoms have equal number of protons and neutrons. The electrons present in outer shell of atom called valence electron.

Inert gases have most stable configuration because the outermost shell of inert gases is completely filled. The valency shell with numbers of electron 2, 8, 18, 32,… are supposed be most stable.

According to another theory, atoms are most stable with number of neucleons 2, 8, 20, 28, 50, 82 and 126. These numbers are also called magic numbers.

FISSION AND FUSION OF AN ATOM

If larger nucleus splits into smaller nuclei, called nuclear fission or if two smaller nuclei combine to make larger nuclei, called nuclear fusion (e.g. in sun, Hydrogen converts into Helium by nuclear fusion).

TO BE CONTINUE…….

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