Test: Periodic Table of Elements - Chemistry MCQ

The elements having similar valence shell electrons have similar chemical properties like reactivity, nature of bonds in their molecules etc. Hence in the modern periodic table, they were grouped in vertical columns called ‘groups’.

Modern periodic table places elements having the same maximum principal quantum number in one period. There are seven periods, though the seventh period consists of many unstable artificial elements.

Non-metals are located at the right end of their respective periods. As we move from left to right in a period or from top to bottom in a group, atomic number increases. Due to increasing charge on the nucleus, atomic size also decreases on moving right in a period. This is also the reason of increasing electronegativity or decreasing electropositivity.

Ground state Uranium and Thorium atoms have partially or totally empty 5f-orbitals. They are members of the actinide family and their naturally occurring isotopes are radioactive.

Radon is a radioactive noble-gas at room temperatures. It is one of densest gases and the only naturally occurring radioactive gas. However, its daughter nuclei are solids. Not many compounds of Radon are known.

As we move down a group, atomic size increases which means that the valence electrons are much farther from the nucleus and hence experience less force of attraction. Hence the electronegativity decreases down the group.

IUPAC has assigned temporary systematic name Ununseptium [= Un(1) +un(1) + sept(7) + ium] to the element with atomic number 117. It belongs to group 17 of the periodic table and is predicted to be a halogen. As of 2015, its discovery has not been officially confirmed.

Due to a small increase in successive ionization enthalpies, most d-block elements exist in multiple oxidation states. However, Zn(I) compounds are very rare and the ion exists in a dimeric form.

Due to the addition of one shell on moving down a group, the neighbourhood of the atom is better shielded by the electrons from an attractive pull of the nucleus.

Ionization energy is the energy required by an isolated gaseous atom to lose the least tightly bound electron to form a cation. It decreases down the group as atomic size increases.