Elements In A Period

Elements In A Period

v  The Change In The Physical Properties of Elements Across Period 3

1)      Proton number increases by one from one element to another element.

2)      Number of valence electron increases by 1.

3)      Physical state change from solid to gas.

4)      Atomic radius (atomic size) of elements decreases because:

Ø  Force of attraction between nucleus and valence electron increases.

Ø  The stronger the force of attraction, the smaller the atomic size.

5)      Electronegativity of element increases because:

Ø  As the size of atom decreases, force of attraction between nucleus and valence electron increases.

Ø  Thus, the strength of the atom to attract electrons to the nucleus increases.

Ø  Metallic properties decrease across the period.

v  The Changes In Oxide Properties of Elements Across Period 3

The properties of the oxide of elements in Period 3 change from basic to acidic

Na2O MgO	Basic oxides	§  Metal oxides are basic. §  Metal oxides dissolve in water to form alkaline solution. v  Example: Na2O (s)  +  H2O (l) →  2NaOH (aq)
Al2O3	Amphoteric	§  Amphoteric means oxide that shows both properties of acid and base. v  Examples: Al2O3 (s)  +  6 HCl (aq) →  2AlCl3 (aq)      +      3H2O (l) Al2O3 (s)   +   2 NaoH (aq)  →  2NaAlO2 (aq)  +  H2O (l)
SiO2 P4O10 SO2 Cl2O7	Acidic	§  Non-metal oxides are acidic. §  Non-metal oxides dissolve in water to form acidic solutions. v  Example: SO2 (s)   +   H2O (l) → H2SO3 (aq)