Core
Periodicity: Chemical Properties
Slide 15 of 31
Pattern Across a
period: Metallic to non-metallic
4. Metals are solids at room
temperature and have high melting temperatures.
–All three metals in this period are solids.
–(Exception: mercury is liquid at room temperature; gallium
and cesium melt just above
room temperature)
Non metals in
general are gases and have low melting points. There are exceptions
of course.
–Silicon,
phosphorus and sulfur in this period are solids, while chlorine is a gas.
5. Metals are good conductors of electricity and heat while
non-metals are not.
–Conductivity
therefore changes from good to poor to no conductivity going across a
period as the elements change from metal to non-metal.
–For
example, in period 3, Na, Mg and Al, being metals, conduct electricity very well.
–Si
which is a metalloid (semi-metal) is a poor conductor, while the rest of the elements
in the period do not conduct because they are all non-metals.