" Atomic structure of the matter "
Previously, We learn that:
*Matter is composed of molecules.
*Molecules are composed
of very smaller units called atoms.
The
atom:
*it is the fundamental
building unit of matter.
*it is the smallest individual unit of matter which can share in chemical reaction.
*it is the smallest individual unit of matter which can share in chemical reaction.
The atomic
construction:
The scientists did many experiments to reach the final idea about the
atomic construction, so they found that the atom consists of:1-Nucleus:
*it is the central core of the atom, where the mass of the atom is concentrated in it.
*it is positively charged because it contains:
-Protons: positively charged particles.
-Neutrons: electrically neutral particles ( uncharged ).
2-Electrons:
*they are negatively charged particles.
*They orbit around the nucleus in energy levels with very high speed, so they don't fall into the nucleus.
Notes:
1-The electron has a negligible mass
relative to that of the proton or neutron, so the mass of the atom is
concentrated in the nucleus.
2-The number of negative electrons which
revolve around the nucleus is equal to the number of positive protons in the
nucleus, so the atom is electrically neutral in its ordinary state.
To express an
atom of any element, we use two terms:
The energy levels:
They are imaginary regions (places) around the nucleus in which the electrons move according to their energies.
*The maximum number of energy levels is seven levels
( in the heaviest atoms ) which are arranged from the nucleus according to their energies as follow:
( in the heaviest atoms ) which are arranged from the nucleus according to their energies as follow:
*Each level has a certain amount of energy increases by the increase of
the level distance from nucleus, this means that:
-The first energy level (K) has the least energy followed by the second (L) and so on.
-The seventh energy level (Q) has the highest energy.
-The first energy level (K) has the least energy followed by the second (L) and so on.
-The seventh energy level (Q) has the highest energy.
Electronic
configuration ( distribution ):
*Each energy
can take a definite number of electrons.
*The number of electrons which saturates the first four energy levels can be calculated from the
relation 2n2, where (n) is the number of the energy level.
*This rule is applied
only on the first four energy levels (K, L, M and N):
The no. of electrons
which saturates the (K) level = 2 × 12 = 2e
The no. of electrons
which saturates the (L) level = 2 × 22 = 8e
The no. of electrons
which saturates the (M) level = 2 × 32 = 18e
The no. of electrons
which saturates the (N) level = 2 × 42 = 32e
Examples: