Question

Element and Atomic Symbol Number Electronegativ (Pauling Scale Atomic Radius (pm) OR 10-12 m 186 Melting Point (C) 98 Boiling Point (°C) 883 11 0.9 12 160 649 1090 1.2 143 663 Sodium (Na) Magnesium (Mg) Aluminium (AI) Silicon (SI) Phosphorus (P) 2467 117 1410 2355 110 44 280 104 119 445 -101 -34 Sulfur (S) Chlorine (CI) Argon (Ar) 3.0 187 1 -189 -186

a) What trend in melting point is evident in the plot?

b) What state would chlorine be in at 25 degrees Celsius?

c) Silicon has the highest melting point. What does this say about the strength of the bonds between silicon atoms?

Answer 1

(а) 1500 Tamperatureck) боо \Ax7

a) the temperature has been shown in Kelvin to avoid negative values of degree celcius. We can convert °C into Kelvin by adding 273. Eg 98°C = (98 + 273)K = 371K and so on.

Melting point increases across the three metals because metallic bond strength increases.

Silicone has highest melting point because it has a giant structure with strong covalent bonds.

Phosphorus exist as P4 having much weeker van der waal forces, so easy to break or melt.

Sulfur exist as S8 , so bigger than P so can der waal forces increases and thus high melting point.

Cl2 has much weaker van der waal forces and exist as Cl2 small molecule. So low melting point.

Ar exist as single argon atom , so least van der waal forces and thus lowest melting point.

b) Chlorine exist as gas at 25°C ( room temperature) because it boils at -34°C.

C) silicone has highest melting point and hence strongest covalent bonds between si atoms.