- There is gradual chemical change across a period.
- The acidity (or basicity) of the oxide of element changes across a period.
- The metallic properties, the electronegativity of element also change across a period.
Acidic Oxide or Basic OxideFrom left to right across a period the oxides change from alkaline/basic (with metals e.g. Na2O) to acidic (with non-metals e.g. SO2).
Metal, Metalloid and Non-metal
- As we go across a period from left to right, the elements change from metals to non-metals.
- There are about 7 elements in the periodic table are classified as semi-metals.
- The metals in the periodic table are mainly found in the left hand columns (Groups 1 and 2) and in the central blocks of the transition elements.
- On the right hand side of the periodic table, there are 7 semi-metals form a staircase like pattern, act as a divider between metal and non-metal.
- The semi-metals are also called the metalloid.
Uses of Metalloids
- The most widely used semi-metals are silicon and germanium.
- It is used to make diodes and transistors in electronic industry.
- Electronegativity is a measure of the potential of atoms to attract electrons to form negative ions.
- Metals have low electronegativities.
- Non-metals have high electronegativities.
- Electronegativities of the elements increase across a period with increasing proton number. This is because
- as the proton number increases, the positive charge of the nucleus will increase accordingly.
- this will increase the ability of the atom to attract electrons from the surrounding and thus increase the electronegativity of the atom.