Podar International School, Jalna

2. Presented By :
Shubham satish nikat
Class: 9th B
Roll No : 33
Chemistry individual project fa-3

6. A cation is a positively charged atom. As you may know, an
atom is electrically neutral. This is because the number of
protons and the number of electrons in an atom are equal, and
the charges balance out. When an atom forms a cation by
losing one or more electrons, it now has
more protons (positively charged particles)
than electrons (negatively charged particles).
You can see all this in action in the diagram below. When
sodium loses an electron, the resulting cation has a +1 net
positive charge. Similarly, when calcium loses 2 electrons, the
resulting cation has a +2 net positive charge.

7. ANION
Anions are atoms or radicals (groups of atoms), that have
gained electrons. Since they now have more electrons
than protons, anions have a negative charge. For
example, Chloride ions Cl- , Bromide Br- , Iodide I-.
These are monovalent anions, meaning they have a
combining capacity with only one ion of Hydrogen.
Similarly there are bivalent anions, etc.
Anions are one of the two types of ions. The other type is
called a cation, and have a positive charge. Ions are atoms
that have an electrical charge.

9. *

11. Formation of
monatomic ions
Monatomic ions are formed by the gain or loss of electrons to
the valence shell (the outer-most electron shell) in an atom. The inner
shells of an atom are filled with electrons that are tightly bound to
the positively charged atomic nucleus, and so do not participate in
this kind of chemical interaction. The process of gaining or losing
electrons from a neutral atom or molecule is called ionization.
Atoms can be ionized by bombardment with radiation, but the more
usual process of ionization encountered in chemistry is the transfer
of electrons between atoms or molecules. This transfer is usually
driven by the attaining of stable ("closed shell") electronic
configurations. Atoms will gain or lose electrons depending on which
action takes the least energy.

12. For example, a sodium atom, Na, has a single electron in its valence shell, surrounding 2
stable, filled inner shells of 2 and 8 electrons. Since these filled shells are very stable, a
sodium atom tends to lose its extra electron and attain this stable configuration,
becoming a sodium cation in the process
Na → Na+
+
e−
On the other hand, a chlorine atom, Cl, has 7 electrons in its valence shell, which is one
short of the stable, filled shell with 8 electrons. Thus, a chlorine atom tends to gain an
extra electron and attain a stable 8-electron configuration, becoming a chloride anion in
the process:
Cl +
e−
→ Cl−
This driving force is what causes sodium and chlorine to undergo a chemical reaction,
wherein the "extra" electron is transferred from sodium to chlorine, forming sodium
cations and chloride anions. Being oppositely charged, these cations and anions
form ionic bonds and combine to form sodium chloride, NaCl, more commonly known as
table salt.
Na+
+ Cl−

14. Formation of polyatomic
and molecular ions
*An electrostatic potential map of the nitrate ion (NO3
−). The 3-dimensional
shell represents a single arbitrary isopotential.
*Polyatomic and molecular ions are often formed by the gaining or losing of
elemental ions such as a proton, H+, in neutral molecules. For example,
when ammonia, NH3, accepts a proton, H+—a process called protonation—it
forms the ammonium ion, NH4
+. Ammonia and ammonium have the same
number of electrons in essentially the same electronic configuration, but
ammonium has an extra proton that gives it a net positive charge.
*Ammonia can also lose an electron to gain a positive charge, forming the
ion ·NH+
3. However, this ion is unstable, because it has an incomplete valence
shell around the nitrogen atom, making it a very reactive radical ion.
*Due to the instability of radical ions, polyatomic and molecular ions are
usually formed by gaining or losing elemental ions such as H+
, rather than gaining or losing electrons. This allows the molecule to
preserve its stable electronic configuration while acquiring an electrical
charge.