With reference to the periodic table, name (a) A halogen element in the fourth period, (b) An

Question:

With reference to the periodic table, name
(a) A halogen element in the fourth period,
(b) An element similar to phosphorus in chemical properties,
(c) The most reactive metal in the fifth period,
(d) An element that has an atomic number smaller than 20 and is similar to strontium.