Each atom consists of a very small nucleus composed of protons and neutrons, which is encircled by moving electrons.
|Position in atom||Inside of atomic nucleus||Inside of atomic nucleus||Revolves around the nucleus|
|Electric charge||Positively charged with value
1.60 X10-19 C
|No charge, Electrically neutral||Negatively charged with value
1.60 X10-19 C
|Mass||Same mass as neutron 9.11X10-27 kg.||Same mass as proton 9.11X10-27 kg.||Less than proton and neutron
|Spin||Inside nucleus||Inside nucleus||Around nucleus|
Each chemical element is characterized by the number of protons in the nucleus, which is called as the atomic number (Z).
Atomic mass = mass of protons mass of neutrons
These are atoms of different elements having the same atomic mass but different atomic number.
How to calculate atomic weight if more than two atomic masses exists?
Atoms of some elements have two or more different atomic masses, which are called isotopes.
Since they are neutral isotopes are elements having same number of electrons, which make them to possess identical chemical properties. Let us see some examples 1H1, 1H2, 1H3 are all isotopes of hydrogen.
Isotones are elements having the same number of neutrons. Examples of isotones are Chlorine – 37 and Potassium – 39. Both have 20 neutrons in their nuclei.
All the elements have been classified according to electron configuration in the periodic table
How elements are arranged?
A rare-earth elements are set of seventeen chemical elements, the fifteen lanthanides, as well as scandium and yttrium.
How name came?
Yttrium, terbium, europium
It is a series of radioactive metallic elements in Group 3 of the periodic table
In order to understand the why materials behave like they do and why they differ in properties, it is necessary that one should look at atomic level.
The study primarily concentrates on two issues:
Atoms are bound to each other by number of bonds.
According to this, atoms can combine either by transfer of valence electrons from one atom to another(gaining or losing) or by sharing of valence electrons in order to have an octet(stable electronic arrangement) in their valence shells.
These inter-atomic bonds are primarily of two kinds
This bond exists between two atoms when one of the atoms is negative (has an extra electron) and another is positive (has lost an electron).
Take bonding in NaCl (rock salt).
In covalent bonding, stable electron configurations are assumed by the sharing of electrons between adjacent atoms.
Bonding in Cl2 molecule
It is found in metals and their alloys.
Type of primary bondings between atoms
For a compound, the degree of either bond type depends on the relative positions of the constituent atoms in the periodic table.
Which bonded materials are electric conductors?
These are also called as physical bonds that are weak compared to primary bonds. Bonding energies are also very less. Secondary bonding exists between virtually all atoms or molecules,
Secondary bonding forces arise from atomic or molecular dipoles.
What are Dipoles?
A dipole may be created or induced in an atom or molecule that is normally electrically symmetric
HCl(Hydrogen chloride molecule)
Van der Waals forces will also exist between adjacent polar molecules. The associated bonding energies are significantly greater than for bonds involving induced dipoles.
The strongest secondary bonding type, the hydrogen bond, is a special case of polar molecule bonding.
Most substances experience an increase in density,up on freezing(i.e transforming from a liquid to a solid with cooling)
One exception is water, which exhibits the anomalous and familiar expansion upon freezing—approximately 9 volume percent expansion.
This behavior may be explained on the basis of hydrogen bonding.
H2O structure in Ice:
Thus, for solid ice, This is a relatively open structure—i.e., the molecules are not closely packed together—and, as a result, the density is comparatively low.
H2O structure in liquid:
This structure is partially destroyed, upon melting and water molecules become more closely packed together. This leads to an increase in density.
Applications of this phenomenon:
Q: What is a directional and non-directional bond?
In directional bonding one bonding atom prefer specific orientations in space relative to one another bonding atom. As a result, molecules in which atoms are bonded covalently have definite shapes.
In non-directional bonding charge is uniform in all direction and because of this an ion is surrounded by other ion from all the direction . This generally happen in case of ionic bonding.