Basic chemistry

 ALKALI METAL  Alkali Metal are   lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr) 1.Physical state of alkali metal  One electron in outermost shell & General formula ns¹.   Francium is radioactive element.  All are silvery white.  Light soft, malleable and ductile metals with metallic lustre.   Alkali metals are paramagnetic, diamagnetic and colourless in form of ions. 2.Atomic size of alkali metal  Biggest in their respective period (except noble gas element)  Size increases from Li to Fr due to addition of an extra shell.  Li < Na < K < Rb < Cs < Fr 3. Softness of alkali metal  Alkali metals are soft because of-  (i) Large atomic size  (ii) BCC crystal structure (HCP in Li)  (iii) Loose packing (68% packing efficiency)  (iv) Weak metallic bond  Cs is the softest metal in s-block 4. Melting point and boiling point of alkali metal  Weak interatomic bonds are due to their large atomic radii and presence of only one valence elect