Chapter 1– Basic Concepts in Chemistry
Chapter 1– Basic Concepts in Chemistry – Quick Revision/Short Notes
High Yield Facts:
- Some important examples [Symbols with Latin or German derivations] Antimony (Sb > Stibium); Silver (Ag > Argentum);Gold (Au > Aurium); Mercury (Hg > Hydragyrum); Lead (Pb > Plumbum);Tungsten (W > Wolfram) etc.
- Dalton > 1st to use term Atom in his “Atomic theory”.
- Berzelius > 1st to distinguish amongst atom and molecules.
- Avogadro > 1st to use term molecule in “Avogadro’s hypothesis”.
- Atom- is “the smallest particle of an element to take part in chemical reaction” whereas molecule “the smallest particle of’ element/compound having»-independent existence.
- The concept of element was first introduced by Robert Boyle.
- A simplest form of substances which can neither be decomposed into nor be composed from simpler substances by ordinary physical and chemical processes is called element.
- Around 114 elements are known, out of which 92 are natural and rest 22 are artificial.
- Artiﬁcial elements can be synthesized by special kind of nuclear process.
- About ¼ of natural elements are free in nature and all other elements are found in nature only in combined state. Eg, H2, 02, N2, Au, Pt etc > free existing_Na, Ca, Zn etc > combined state.
- Four most abundant elements on earth crust: O2>Si>Al>Fe
- Electropositive in character and exist in solid state (except Hg).
- Malleable, lustrous and ductile.
- High melting and boiling point.
- Good conductor of heat and electricity
- Ag, Cu, Au, Fe, Na etc.
- Electronegative in nature and exist in all three states eg. C-solid, Br2 – liquid, Cl2 -gas.
- Neither malleable nor ductile.
- Non-lustrous (except iodine)
- Low melting and boiling point except diamond
- Showing the characteristics in between metal and non-metal. Eg. As, C, Sb, Ge, Te etc.
- Compounds “are formed’ by chemical union of 2 or more elements in fixed proportion by weight.
- Atomic number = no. of protons.
- Mass number = no. of nucleons = no. of protons + no. of neutrons.
- Atomic weight = Average of the product of isotropic mass and relative abundance.
- If an element has x % of A isotope & y % of B isotope.
Then, At. wt= x % of A + y % of B
(where, A & B are respective mass numbers of isotopes).
- For an element zXA,
No. of electrons = no. of protons =Z & No. of neutrons = A – Z.
- Fractional atomic weight of an element is because of existence of isotopes.
- Radius of an atom is of the order 10-8cm (10-10m).
- Radius of an atomic nucleus is of the order1O-12cm (10-14m)
- This is why, the size of nucleus is said to be negligible when compared» to that of an atom.
- Species having same atomic number (same no. of protons) but different mass number.
- Isomers have different radioactive properties.
- Isomers have different no. of neutrons.
- Species having same no. of neutrons.
- lsotones have different no. of protons.
- Species having same no. of nucleons.
- They have different number of-neutrons (n), different number of proton(P) but
n1 + p1= n2+ p2
- They have same mass no. but different atomic number.
- Species having same difference of neutron and proton (n-p).
- An alpha-decay produces isodiaphere as compared to the parent atom.
Isoelectronic: Atoms or radicals having same number of electrons.
Isoatomic: Molecules having same number of atoms.
Same atomic number but different mass number.
1H1 1H2 1H3
Proton Deuterium Tritium
- An element has mass 14 and number of neutrons 8 then it is an isotope of carbon.
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