SPM Form 4: Periodic Table of elements (Checklist)

• Periodic Table: the table showing the elements in order of increasing proton number; similar elements are arranged in columns called groups.
• Group: A vertical column of elements in the Periodic table.
• Period: A horizontal row of the Periodic Table; its number tells you how many electron shells there are.
• Alkali metals: the Group I elements of the Periodic Table, which include lithium, sodium, potassium, rubidium, caesium and francium.
• Alkaline earth metals: the Group II elements of the Periodic Table, which include beryllium, magnesium, calcium, strontium, barium, and radium.
• Halogens: the Group VII elements of the Periodic Table, which include fluorine, chlorine, bromine, iodine and astatine.
• Noble gases: the Group 18 elements of the Periodic Table; they are called ‘noble’ or inert gases because they are so unreactive, which include helium, neon, argon, krypton, xenon and radon.
• Transition elements: the elements in the wide middle block of the Periodic Table (elements in group 3 to group 12).
• Metal: an element that shows metallic properties (for example conducts electricity, and forms positive ions)
• Non-metal - an element that does not show metallic properties: the non-metals lie to the right of the zig-zag line in the Periodic Table.
• Amphoteric oxide: An oxide that exhibits both acidic and basic properties.
• The atomic radius is a term used to describe the size of the atom.
• The ionization energy is the energy required to completely remove an electron from a gaseous atom or ion.
• Electron affinity reflects the ability of an atom to accept an electron. It is the energy change that occurs when an electron is added to a gaseous atom.
• Electronegativity is a measure of the attraction of an atom for the electrons in a chemical bond. The higher the electronegativity of an atom, the greater its attraction for bonding electrons.

Explain how the melting and boiling points change when going down the Group 1.

Melting and boiling points of alkali metals decreases when going down Group 1. The atomic size of alkali metals becomes bigger when going down the group 1. Hence, the forces between alkali metal atoms are weaker when going down Group 1. Hence, less heat energy is required to break the weaker forces.

Overview of Periodic Table

• Alkali Metals (Group 1) : All group 1 metals have one valence electron. When they form ions, they will have a charge of 1+. Group 1 alkali metals are highly reactive and will react vigorously with water.

• Alkali Earth Metals (Group 2): All group 2 metals have two valence electrons. When they form ions, they will have a charge of 2+. Group 2 alkaline earth metals are highly reactive and will react with water.

• Transition Metals (Groups 3–10, d block): Transition metals are famous for the colored salts and colored solutions they form. Many gems contain numerous transition metals. It is hard to predict the charge of a transition metal ion because the transition metals have multiple oxidation states. One transition metal, Hg, exists as a liquid at room temperature.

• Halogens (Group 17): Halogens (salt formers) have seven valence electrons and form ions with a charge of 1−. The halogens exist in three phases at room temperature. Fluorine is a pale-yellow gas, chlorine is a green gas, bromine is a brown-orange liquid, and iodine is a purple solid.

• Noble (Inert) Gases (Group 18): Noble gases have a full outer shell and will not react to form ions or share electrons.

• Lanthanides and Actinides (f Block): These elements have their valence electrons located in the f orbitals and are radioactive in nature.

The alkali metals - trends in reactivity

As you go down the group, the atomic number of the alkali metals increases, and their properties change:

• their melting points decrease
• their densities increase
• they become softer
• they become more reactive

The alkali metals are soft, reactive metals. They react vigorously with water and become more reactive as you go down the group.

Reaction of Alkali Metals with Oxygen gas

Alkali metals are more reactive in their reactions with oxygen when going down Group 1. Lithium, sodium and potassium react with oxygen gas, O₂ to form solid metal oxides with alkaline properties. Alkali metals react quickly with oxygen and are stored under oil to prevent oxygen from reaching the surface of the bare metal.

• Lithium burns slowly with a red flame. White fumes are produced which become a white solid when cooled to room temperature. The white solid formed dissolves in water to form a colorless solution that turns a red litmus paper blue. 

4Li _(s) + O_{2 (g)} → 2Li₂O _(s)

• Sodium burns rapidly with a bright yellow flame. White fumes are produced which become a white solid when cooled to room temperature. The white solid formed dissolves in water to form a colorless solution that turns a red litmus paper blue. 

4Na_(s) + O_{2 (g)} → 2Na₂O_(s)

• Potassium burns very rapidly and violently with a lilac flame. White fumes are produced which become a white solid when cooled to room temperature. The white solid formed dissolves in water to form a colorless solution that turns a red litmus paper blue. 

4K_(s) +    O_{2 (g)} → 2K₂O(s)

Reaction of Alkali Metals with Water

Alkali metals are more reactive in their reactions with water when going down the group. Group 1 elements react with water to form an alkaline metal hydroxide solution and hydrogen gas, H₂.

• Lithium melts and moves slowly at random on the surface of water with plenty of fizz. A colorless solution that turns red litmus paper blue is formed. 

            2Li _(s) + 2H₂O _(l) → 2LiOH _(aq) + H_{2 (g)}

• Sodium melts and moves rapidly at random on the surface of water with a hissing sound. A colorless solution that turns red litmus paper blue is formed. 

2Na _(s) + 2H₂O _(l) → 2LiOH _(aq) + H_{2 (g)}

• Potassium melts moves very fast at random on the surface of water and ignites with a lilac flame, with ‘pop’ and hissing sounds. A colorless solution that turns red litmus paper blue is formed. 

2K _(s) + 2H₂O _(l) → 2KOH _(aq) + H_{2 (g)}

The arrangement of the Group 1 elements in ascending order of their reactivity is lithium, sodium and potassium. 

Alkali Metal on the Periodic Table

The alkali metals are the elements located in Group IA of the periodic table. The alkali metals are lithium, sodium, potassium, rubidium, cesium, and francium. Alkali metals have one electron in their outer shell, which is loosely bound. This gives them the largest atomic radii of the elements in their respective periods. Their low ionization energies result in their metallic properties and high reactivities. An alkali metal can easily lose its valence electron to form the univalent cation. Alkali metals have low electronegativities. They react readily with nonmetals, particularly halogens.

Summary of Common Properties

·         Lower densities than other metals

·         One loosely bound valence electron

·         Largest atomic radii in their periods

·         Low ionization energies

·         Low electronegativities

·         Highly reactive