Metals & Non-metals

Formation of chemical bond by metal and non-metal

A metal reacts with non-metal by formation of bonds such bonds are called chemical bonds.

Chemical bonds are formed in following ways:

(a) By transfer of electrons

(b) By sharing of electrons

Chemical Bond formation by transfer of electrons

There are two or more than two atoms are required for the bond formation by transfer of electrons. In transfer of electrons one atom loses electron or electrons and other atom gains electron. Atom which loses electron is called donor and that gains electron is called acceptor.

Chemical bond formed by transfer of electrons is called Ionic Bond. Ionic Bond is called Electrovalent Bond also.

Atom forms ion by losing or gaining of electron. After losing or gaining of electron, an atom becomes electrically charged.

Ions

Atoms that are electrically charged are known as ions. For example: sodium ion (Na⁺), potassium ion (K⁺), magnesium ion (Mg⁺⁺), Chloride ion (Cl^–), oxide ion (O^2–)), etc.

Types of Ions

Ions further can be divided into two types: positive ions and negative ions

Positive Ions or Cations

Atoms having positive charge over them are called positive ions or Cations.

Formation of positive ions

An atom gets positive charge over it by losing of electron. Number of positive charge over atom is equal to number of electrons lost.

Example

(1) Hydrogen Ion (H⁺)

When hydrogen atom loses one electron, it becomes positively charged and it is called hydrogen ion. Since, hydrogen loses one electron thus number of positive charge over hydrogen is +1 (plus one).

H – e^– = H⁺

(2) Sodium ion (Na⁺)

Na – e^– = Na⁺

(3) Calcium ion (Ca^{+ +})

Ca – 2e^– = Ca^{+ +}

Since, valence electron of calcium is equal to 2 (two), thus calcium loses two electrons in order to achieve stable configuration.

(4) Magnesium ion (Mg^{+ +})

Mg – 2e^–= Mg^{+ +}

Magnesium also has two electrons in its outermost orbit, thus magnesium loses two electrons to achieve stable configuration.

Negative Ions or Anions

Negatively charged ions are called negative ions or anions.

An atom becomes negatively charged after gains of electrons. Number of negative charge over atom is equal to number of electrons gains.

Example:

(1) Chloride Ions (Cl ^–)

Cl + e^– = Cl ^–

Chlorine has seven electrons in its outermost orbit, thus to achieve stable configuration, i.e. to acquire 8 (eight) electrons in its outermost orbit, chlorine has always tendency to gain one electron.

(2) Oxide Ion (O ^– –)

O + 2e^– = O ^{– –}

Oxygen has six electrons in its outermost orbit, thus oxygen has always tendency to gain two electrons and complete eight electrons in its outermost orbit. After gaining of two electrons, oxygen acquire two negative charges over it, ion so formed by oxygen is called oxide ion.

Cause of Positive or Negative Charge over an atom

Electrons are negatively charged particles and protons are positively charged particles. An atom is electrically neutral because number of protons is equal to number of neutrons in an atom.

But, when an atom loses one electrons, the number of protons becomes one more than that of number of electrons, so this extra number of proton which is positively charged is caused for one positive charge over an atom.

Atomic number of an atom = Number of electrons = Number of protons

Example

Hydrogen

Atomic number = 1

Number of electron = 1

Number of proton = 1

After losing one electron by hydrogen atom

Number of electrons becomes equal to zero (0) while number of proton remains equal to one (1). This creates one positive charge over hydrogen atom, i.e. hydrogen ion (H⁺).

Chlorine

Atomic number of chlorine = 17

Number of electrons in chlorine atom = 17

Number of protons in chlorine atom = 17

When chlorine atom gains one electron

Number of electrons becomes equal to 18 while number of proton remains equal to 17. Thus, negative charge in chlorine becomes one more than that of positive charge. This creates one negative charge over chlorine atom, i.e. chlorine becomes chloride ion (Cl ^–).

Oxygen Atom

Atomic number of oxygen = 8

Number of electrons in oxygen atom = 8

Number of protons in oxygen atom = 8

When oxygen atom gains two electrons, the number of electrons becomes equal to 10 while number of protons remains equal to 8. This means number of negative charge becomes two more than that of number of positive charge. Because of this after losing two electrons, oxygen atom gets two negative charges over it, i.e. oxygen forms oxide ion (O^– –).