Atoms and Molecules

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04 Symbols of Element’s

DALTON’S SYMBOLS OF ELEMENTS:

 

  • Dalton’s was the first scientist to use the symbols to represent elements in a short way.
  • Berzilius suggested that the symbols of elements be made from one or two letters of the name of the element.
  • The first letter of symbol is always written as a capital letter and the second letter as a small letter.

Symbols Derived from English Names of the Elements

English name

of the element

Symbol English name

of the element

Symbol
1. Hydrogen   H 14. Sulphur   S
2. Helium   He 15. Chlorine   Cl
3. Lithium   Li 16. Argon   Ar
4. Boron   B 17. Calcium   Ca
5. Carbon   C 18. Manganese   Mn
6. Nitrogen   N 19. Nickel   Ni
7. Oxygen   O 20. Zinc   Zn
8. Fluorine   F 21. Bromine   Br
9. Neon   Ne 22. Krypton   Kr
10. Magnesium   Mg 23. Iodine   I
11. Aluminium   Al 24. Barium   Ba
12. Silicon   Si 25. Cobalt   Co
13. Phosphorous   P 26. Uranium   U

Symbols Derived from Latin Names of the Elements

English name

of the element

Symbol Latin name of

The element

1. Sodium   Na Natrium
2. Potassium   K Kalium
3. Iron   Fe Ferrum
4. Copper   Cu Cuprum
5. Silver   Ag Argentum
6. Gold   Au Aurum
7. Mercury   Hg Hydragyrum
8. Lead   Pb Plumbum
9. Tin   Sn Stannum

ATOMIC MASS OF AN ELEMENT

    • Matter is made up of atoms that have certain amount of mass.
    • Atomic mass is the mass of an atomic particle and is commonly expressed as per the international agreement in terms of a unified atomic mass unit (amu).
It can be defined as 112th  of the mass of carbon12  atom in its ground state.
  • Carbonatom has been assigned an atomic mass of exactly 12 atomic mass units.

 

Atomic mass unit =112 th of the mass of a carbon12 atom

Or

1u =112th the mass of a carbon12 atom

 

  • The atomic masses of all other elements are determined by comparing the mass of their atom with the mass of a
    carbon12 atom
  • The atomic masses of elements vary from 008 amu for hydrogen up to 250 amu for elementswhich have a very high atomic number.
  • The mass of an atom is the sum of mass of protons and neutrons which is almost equal to the atomic mass.
  • The small change is due to the binding energy mass loss.
1amu = 1.66 × 1024 g
  • The atomic weight of an atom is a dimensionless number when it is divided by unified atomic weight or Daltons giving the relative isotropic mass.
  • The addition of average atomic mass of each atom in the molecule gives the mass of molecules.

Atomic masses of a few elements

 

Element

Atomic mass (u)

Hydrogen

1

Carbon

12

Nitrogen

14

Oxygen

16

Sodium

23

Magnesium

24

Sulphur

32

Chlorine

35.5

Calcium

40

HOW DO ATOMS EXIST?

·         Atoms of most of the elements are chemically very reactive and so they do not exist in Free State

 H   However, atoms of few elements called noble gases like helium, neon, argon and krypton, etc. are chemically unreactive and exists in the free state.

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