Summary of what I learnt ( Periodic Table)

In the periodic table, the elements are arranged in order of increasing proton (atomic) number, and are classified according to groups and periods.

Group – a vertical set of elements

Period – a horizontal row of elements

Group:

The groups in the Periodic Table are numbered from I to IV and then Group 0. Some of these groups have names too:

Group I: Alkali metals

Group II: Alkaline earth metals

Group VII: Halogens

Group 0: Noble gases

Elements between Group II and III are known as transition metals or transition elements. Element in the same group will have similar chemical properties and will undergo the same type of chemical reactions.

Period:

Each period is numbered, 1, 2, 3 etc. Elements in the 1^st period will only have their 1^st shell fully/partially occupied with electrons. Elements in the 2^nd period will have their 1^st shell fully occupied with electrons, and their 2^nd shell fully/ partially occupied with electrons.

Patterns in the Periodic Table:

Electronic Structure

Down each group, the number of valence electrons is the same for each element and is equal to the group number.

Example: Group I Elements

Li = 2.1

Na = 2.8.1

K = 2.8.8.1

Metals and Non-metals

Across the period, the properties of elements change from metallic to non-metallic. Generally, elements with small number of electrons in the valence shells (eg. Group I and Group II) are metals. Elements with large number of electrons in the valence shells (eg. Group VII and 0) are non-metals.

The line that divides metals from non-metals runs diagonally through the Periodic Table. Elements found beside this dividing line are known as metalloids. Metalloids have the same properties of non-metals and metals.

Charges on ions

[Refer to the pictures above]

Charges on the ions formed are related to the group number and number of valence electrons. Elements are on the left side of the Periodic Table lose their valence electrons to form cations with charges corresponding to their group number. Elements on the right side of the Periodic Table gain electrons to form anions. The charges on the anions are corresponding to the number of electrons gained to fill their valence shells with 8 electrons.