Periodic Table: History, Groups, Periods and Trends

Attempt the quiz above first, then review every question with its correct answer and a short explanation below.

1. Q1.In the modern periodic table, elements are arranged in order of increasing:

   • A.atomic number✓ Correct Answer
   • B.atomic mass
   • C.density
   • D.melting point

   Explanation: This is the modern periodic law.

2. Q2.The first widely accepted periodic table was proposed by:

   • A.Dmitri Mendeleev✓ Correct Answer
   • B.Henry Moseley
   • C.John Dalton
   • D.Niels Bohr

   Explanation: He arranged elements by atomic mass in 1869.

3. Q3.The modern periodic table has how many groups?

   • A.8
   • B.7
   • C.16
   • D.18✓ Correct Answer

   Explanation: Groups are vertical columns.

4. Q4.The modern periodic table has how many periods?

   • A.8
   • B.7✓ Correct Answer
   • C.18
   • D.5

   Explanation: Periods are horizontal rows.

5. Q5.Which of the following is a noble gas?

   • A.hydrogen
   • B.helium✓ Correct Answer
   • C.nitrogen
   • D.oxygen

   Explanation: Noble gases have complete outer shells.

6. Q6.The most electronegative element is:

   • A.chlorine
   • B.fluorine✓ Correct Answer
   • C.oxygen
   • D.nitrogen

   Explanation: Fluorine strongly attracts shared electrons.

7. Q7.The modern periodic law is based on the work of:

   • A.Dmitri Mendeleev
   • B.Henry Moseley✓ Correct Answer
   • C.Antoine Lavoisier
   • D.Lothar Meyer

   Explanation: Moseley showed atomic number is the fundamental property.

8. Q8.The elements of Group 1 (except hydrogen) are called:

   • A.alkaline earth metals
   • B.halogens
   • C.alkali metals✓ Correct Answer
   • D.noble gases

   Explanation: They include lithium, sodium and potassium.

9. Q9.The elements of Group 17 are called:

   • A.halogens✓ Correct Answer
   • B.alkali metals
   • C.chalcogens
   • D.noble gases

   Explanation: They include fluorine, chlorine, bromine and iodine.

10. Q10.The lightest metal is:

    • A.sodium
    • B.aluminium
    • C.magnesium
    • D.lithium✓ Correct Answer

    Explanation: Lithium is less dense than water.

11. Q11.Across a period from left to right, the atomic size generally:

    • A.increases
    • B.stays constant
    • C.doubles
    • D.decreases✓ Correct Answer

    Explanation: Nuclear charge rises while shells stay the same.

12. Q12.Down a group, the reactivity of alkali metals:

    • A.decreases
    • B.stays constant
    • C.increases✓ Correct Answer
    • D.becomes zero

    Explanation: The outer electron is held more loosely.

13. Q13.Which element has the highest first ionisation energy?

    • A.sodium
    • B.oxygen
    • C.helium✓ Correct Answer
    • D.carbon

    Explanation: Its small size and full shell hold electrons tightly.

14. Q14.Which non-metal is liquid at room temperature?

    • A.bromine✓ Correct Answer
    • B.chlorine
    • C.iodine
    • D.sulphur

    Explanation: Bromine is a reddish-brown liquid.

15. Q15.Which metal is liquid at room temperature?

    • A.lead
    • B.mercury✓ Correct Answer
    • C.zinc
    • D.tin

    Explanation: Gallium melts just above room temperature.

16. Q16.The f-block elements placed at the bottom of the table are the:

    • A.alkali metals
    • B.halogens
    • C.noble gases
    • D.lanthanides and actinides✓ Correct Answer

    Explanation: They fill the 4f and 5f subshells.

17. Q17.Mendeleev's "eka-aluminium" was later discovered as:

    • A.germanium
    • B.scandium
    • C.gallium✓ Correct Answer
    • D.indium

    Explanation: The match with his predicted properties confirmed his table.

18. Q18.Which element has the highest electron affinity?

    • A.fluorine
    • B.oxygen
    • C.chlorine✓ Correct Answer
    • D.bromine

    Explanation: Fluorine's small size causes electron repulsion that lowers its value.

19. Q19.A diagonal relationship exists between lithium and:

    • A.sodium
    • B.calcium
    • C.aluminium
    • D.magnesium✓ Correct Answer

    Explanation: Their sizes and charge densities are similar.

20. Q20.Transition elements belong to the:

    • A.d-block✓ Correct Answer
    • B.s-block
    • C.p-block
    • D.f-block only

    Explanation: They are found in groups 3 to 12.