Group 14 Elements
Almost all properties will show a normal trend from C to Si, But, beyond Si, the trend or change slows down due to ineffective screening caused by d and f electrons.
Density: It increases down the group. C has higher density than Si due to its diamond form.
M.Ps and B.P.s: They will decrease down the group due to decrease in the inter atomic attraction. C has highest M.P and B.P in the entire periodic table.
Atomic radius: Increases down the group.
Ionisation potential: It decrease normally from C to Si. Thereafter, the decrease is very slow.
Electronegativity: It decreases normally from C to Si but there after, it remains constant.
Catenation
The ability to form long chains or rings by the atoms of an element is called catenation. Catenation ability decreases due to decrease in the bond energy. Thus, C has highest catenation than any other element in the periodic table.