Which of the following is a naturally occurring radioactive element? MCQ with Answer and Explanation

Explanation:
Bronze is Cu + Sn. Brass is Cu + Zn. Solder is Pb + Sn. Duralumin is Al + Cu + Mg. Bronze was one of the earliest alloys used by humans.

Explanation:
Magnesium (Z=12): configuration 2,8,2. Period = number of shells = 3; Group = 2 (2 valence electrons). Be is Group 2, Period 2; Ca is Group 2, Period 4; Sr Period 5.

Explanation:
A catalyst lowers the activation energy (Ea) by providing an alternative reaction mechanism, thereby increasing the rate of both forward and reverse reactions equally. It does not affect the equilibrium constant, enthalpy change (ΔH), or the position of equilibrium. It remains chemically unchanged after reaction. Positive catalysts speed up, negative catalysts slow down. Enzymes are biological catalysts.