Lesson 5:Periodic Table

Lesson 5: Periodic Table Behavioural objectives: at the end of the lesson, you should be able to 1. Define periodic table 2. State the modern periodic law 3. Discuss the blocks of elements with examples 4. State the group/family of elements on periodic table and name the member of each family. What is periodic table? Periodic table is a chat that shows the arrangement of elements based on their atomic number and chemical properties.

The modern periodic law The modern periodic law states that “chemical properties of elements are a periodic function of their atomic numbers”. The blocks of elements There are four blocks of elements on the periodic table which are: S-block P –block D-block F-block S-block elements: these are elements that their electronic configuration ends on s – orbitals, they can be found on group 1 and 2 of the periodic table. See the image above. They include: hydrogen, lithium, beryllium, sodium, potassium. e.t.c. there electronic configuration looks like this: 1s2,2s2 2p6,3s1 (K) P-block elements: these are elements that their electronic configuration ends on P – orbital. They are located between group 3/13 to 8/18 of the periodic table. That is from aluminium group to the noble gases. D – block elements: these are elements that there electronic configuration ends on d – orbitals, they are also called the transition elements. They are located between group 2 and 3 of the periodic table. Starting from scandium (Sc) to zinc (Zn). See image above. F-block elements: these are the elements that their electronic configuration falls on F orbitals. They are referred to as inner transition elements. They can be found between period 6 and 7 of the periodic table. They are also referred to as lanthanide and actinide series. Isolated to the bottom of the periodic table in the diagram above.

METALS, METALLOIDS AND NON –METALS

Apart from grouping the elements using their blocks, we can also group elements on periodic table into metals, metalloids and non metals.

Metals: these are elements that can give away electrons to become positively charged, they can conduct heat and electricity. They are located between group 1 to 13 of the periodic table. That is from group sodium to aluminium. (see the table above).

Non- metals: these are elements that do accept electron from other elements in order to complete their outermost shell. They do not conduct electricity and heat. They are found between group 14 to 18.ofthe periodic table. That is from carbon to the noble gasses.

Metalloids: these are elements that their characteristics are intermediate between metals and non metals. That is are not completely metals nor complete non-metals in their behaviour. They are found between group 12 to 16 of the periodic table. (see the image above for clarifications).

GROUP AND PERIODS OF ELEMENTS

The most popular and main classification of the periodic table is the group and period. Elements are classified into groups based on the number of electrons they have on their outer most shell while they are also classified into periods based on the number of shells they have.  All elements in a particular group have the same number of electrons in their outer most shell  and all elements in a particular periods have the same number of shell. The group is the vertical column of the periodic table while the horizontal row is the period. There are 8 groups and seven periods on the modern periodic table.

GROUPS AND THEIR PROPERTIES

GROUP ONE ELEMENTS

1.      They include H, Li, Na, K, Rubidium, Caesium and Francium

2.      They are called alkaline metal  

3.      They have 1 electron in their outermost shell

4.      They are all metals which are strongly electropositive except for hydrogen which is a gas but have the atomic number of 1.

5.      They are readily ionized by loss of the single valence electron to become a uni-positive ion.

6.      They are very reactive and form very stable electrovalent compounds

7.      They are good reducing agents

GROUP TWO ELEMENTS

1.      They include Be, Mg, Ca, Sr, Ba and Ra

2.      They are also called alkaline earth metal

3.      They have two valence electrons and ionize by the loss of the two valence electrons to form bivalent ions

4.      They are all metals but less reactive than group one elements. Their  reactivity increases down the group

5.      They are good reducing agents.

GROUP THREE ELEMENTS

1.      They include B, Al, Ga, In and thallium

2.      They have three electrons in their outermost shell

3.      They form weakly electrovalent compounds with Non-metal

4.      Boron is a non- metal, forming covalent bond while Aluminium is a metal.

GROUP FOUR ELEMENTS

   Group 4 elements are quite mixed. Metallic properties increases down the group, while carbon is a non –metal, Silicon and Germanium are metalloids, Tin and Lead are metals.

            However, both Silicon and Lead form amphoteric oxides.

Group five elements

            This the Nitrogen family, Nitrogen is a gas at room temperature, Phosphorus is a solid, while Antimony and Bismuth are metals.

GROUP SIX ELEMENTS

1.      This group also include both non-metals and metals.

2.      Oxygen and Sulphur are non-metals while Selenium and Tellurium are metals.

GROUP SEVEN ELEMENTS

1.      They are popularly known as HALOGENS

2.      They include Fluorine, Chlorine, Bromine, Iodine and Astatine.

3.      They are highly electronegative

4.      They have seven electrons in their outer most shell.

5.      Their electronegativity decreases down the group. However, Fluorine is most Electronegative Element and the most reactive of all the elements.

GROUP EIGHT ELEMENTS:

1.      They are called the noble gases

2.      They are all gas at room temperature

3.      They include, Helium, Neon, Argon, Krypton, Xenon and Radon

4.      They have completely filled shell and hence, they are all unreactive.

TRANSITION ELEMENTS

Between group 2 and 3 is a block of elements which shows similar and strange behaviour the other metals. They are called the transition elements. They are all metals with metallic properties. Their strange behaviour include:

1.      Variable oxidation state

2.      Paramagnetic in nature

3.      Formation of coloured compound

4.      Catalytic ability.

5.      They include: Scandium, Titanium, Vanadium, Chromium, Manganese, Iron, Cobalt, Nickel, Zinc.

LANTHANIDE AND ACTINIDE

            Apart from the various groups of elements discussed so far, there are set of another element isolated below the periodic table. They are originally located between period six and seven. These elements are called the lanthanide and the actinide series respectively. (See the table above) they start from Lanthanum to Lawrencium.