Question 1 What are metalloids. Give example?
Question 2 Write few characteristics of metals?
Question 3 write few characteristics of non-metals?
Question 4 Give examples of metals?
Question 5 Give examples of non-metals?
Question 6 How many metals are known to us?
Question 7 How many non-metals are known to us?
(1) Metals are malleable.
(2) Metals are ductile.
(3) They are good conductor of heat and electricity.
(4) They are lustrous or shiny.
(5) They are hard and strong.
(6) They cannot be cut easily.
(7) They are solids except mercury which is a liquid.
(8) They have high melting and boiling point.
(9) They have high densities.
(10) They are sonorous.
For Example: Iron, copper, aluminium, zinc, gold, silver, sodium, potassium, nickel, cobalt, tin, mercury etc.
There are 70 metals.
(1) Non-Metals are not malleable.
(2) Non-Metals are not ductile.
(3) They are bad conductor of heat and electricity.
(4) They are not lustrous or shiny.
(5) They are not hard and strong.
(6) They can be cut easily.
(7) They are solids, liquid and gases at room temperature.
(8) They have low melting and boiling point.
(9) They have low densities.
(10) They are not sonorous.
For Example: Carbon, sulphur, helium, hydrogen, phosphorus, fluorine, chlorine etc.
There are 22 non-metals. Out of these 10 are solids,1 non-metal is a liquid whereas 11 non-metals are gases.
The elements whose properties are intermediate between those of metals and non-metals are known as metalloids.
For Example: Silicon, Germanium, Arsenic, Tellurium.
Skills to Develop
Remember that non-metals are on the right and top of the periodic table. Based on the periodic trends in the last 4 sections, this means that they are usually smaller, more likely to gain electrons, and less likely to lose electrons, than the metals.
In the elemental form, non-metals can be gas, liquid or solid. They aren't shiny (lustrous) and they don't conduct heat or electricity well. Usually their melting points are lower than for metals, although there are exceptions. The solids usually break easily, and can't bend like metals. It's a general pattern that the closer an atom is to the noble gas electron configuration, the fewer bonds it makes. Non-metals are close to the noble gas configuration, so they usually make a few bonds to a few neighbors. The noble gases make no bonds, and are monatomic (single atoms); halogens make 1 bond to 1 other atom, etc. This means that they don't usually form extended structures (except diamond and graphite). Instead, they form separate molecules. These molecules aren't held together tightly, so solids can easily melt or break. The electrons are held tightly by just 1 - 2 atoms, so they can't conduct electricity.
Non-metals can react with each other to form compounds in which electrons are shared. These compounds have some of the same characteristics as the elementals forms: usually they melt or boil at relatively low temperature and don't conduct heat or electricity. When non-metals react with metals, they usually gain electrons to form anions. The cations are then attracted to the anions, so the result are ionic or sort of ionic compounds. The more a non-metal wants to gain electrons, the more reactive it is. Thus, the halogens are all reactive, but iodine is pretty safe, while bromine, chlorine and especially fluorine are really nasty and dangerous! Oxygen only seems safe and friendly to us because we are adapted to it. When oxygen first appeared in the atmosphere due to photosynthesis, most of the early life forms probably died from it; we descended from the survivors.
Contributors and Attributions
Emily V Eames (City College of San Francisco)