4.3 Group 1 Elements

Physical properties
■ Elements of Group 1

	►	Lithium, Li Natrium, Na Kalium, K Rubidium, Rb Caesium, Cs Francium, Fr
	►	The following mnemonic method can be used to memorize the sequence of elements in Group 1. ○ Little Nasty Kids Rub Cat's Fur

■ Physical properties of alkali metals

	►	All alkali metals are grey in colour with shining surfaces just like other metals.
	►	All alkali metals are soft and can cut easily. Elements Density (gcm-3) Melting point (℃) Boiling point (℃) Atomic radius (nm) Lithium, Li 0.534 186 1609 0.133 Natrium, Na 0.970 98 880 0.157 Kalium, K 0.860 64 760 0.203 Rubidium, Rb 1.530 39 700 0.216 Saesium, Cs 1.900 29 670 0.235
	►	All alkali metal conduct heat and electricity.
	►	All alkali metals have high melting and boiling point. ○ The melting and boiling point are not as high as other metals. ○ The melting and boiling point decrease down the group. This is because as the atomic radius increases, the bonds between the atoms become weaker.
	►	The atomic radius and density of elements increase down the group. ○ An increase in the number of filled electron shells will result in increased atomic size, mass and density.
	►	The animation below shows the changes in physical properties of Group 1 elements down the group.

Chemical properties
■ Arrangement of electron in alkali metals.

Element Electron configuration Arrangement of electron Lithium 2.1 Natrium 2.8.1 Kalium 2.8.8.1 Rubidium 2.8.18.8.1 Caesium 2.8.18.18.8.1

■ Chemical reaction.

	►	Alkali metals are very reactive elements and therefore must be kept in paraffin.
	►	All alkali metals shows similar properties when reacting with certain compounds. ○ All alkali metals react vigorously with water to produce alkaline metal hydroxide solution and hydrogen gas. Laboratory Activity 4.3.1: Studying the reaction of alkali metals with oxygen ○ All alkali metals burn in oxygen gas rapidly to produce solid metal oxides. Laboratory Activity 4.3.2: Studying the reaction of alkali metals with water ○ All alkali metals burn in halogen gas rapidly to produce white solid metal halides. Laboratory Activity 4.3.3: Studying the reaction of alkali metals with halogen
	►	Brief explanation on the reaction of alkali metals. ○ All alkali metals have one valence electron. ○ They donate this electron to attain the noble gas stability. $Y\to Y^{\text{+}}+e^{\text{-}}$
	►	The reactivity of alkali metals increases as down the group.
	►	The animation below shows the explanation on the changes on the reactivity of alkali metals.

■ This video contains information about the physical properties and the reactions of the Group 1 elements.

← 4.2 Group 18 Elements

4.4 Group 17 Elements →

⇲ For exercise(objective and subjective), download for free on Android OS.