Which of the following trends is observed in Group 1 (alkali metals) down the group?
A. Ionization energy increases
B. Reactivity decreases
C. Atomic radius increases
D. Electronegativity increases
Answer: Option C
Solution (By JKSSB Mock Tests)
Down Group 1 (Li → Fr), atomic radius increases due to addition of electron shells. Ionization energy and electronegativity decrease. Reactivity with water increases because the outer electron is more easily lost. Density generally increases, melting/boiling points decrease. Cesium and francium are most reactive. The increase in radius is due to principal quantum number increase.
Explanation:
Permanent hardness is due to dissolved sulfates and chlorides of calcium and magnesium. Boiling does not remove it. It requires chemical treatment (washing soda, ion exchange) or distillation. Temporary hardness (bicarbonates) is removed by boiling.
Explanation:
Atomic number is the number of protons, which is 17 for all chlorine atoms. Mass numbers differ due to different neutrons (18 and 20). Isotopes have same atomic number, different mass number.
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