Carbon-14 (half-life ~5730 years) is used to determine the age of archaeological and geological organic samples up to ~50,000 years. Cobalt-60 for cancer; Am-241 for smoke detectors.
Explanation:
Atomic number (Z) is the number of protons in the nucleus, which defines the identity of the element. In a neutral atom, the number of electrons equals Z. Neutrons contribute to mass number but not atomic number. Isotopes have same Z but different number of neutrons. Nucleons are total protons + neutrons = mass number. The modern periodic table is based on atomic number.
Explanation:
Chadwick (1932) produced highly penetrating neutral radiation by bombarding Be with α-particles, identified as neutrons. Reaction: ⁹Be + ⁴He → ¹²C + ¹n.
Assertion (A): Aluminum is highly reactive but is used for making cooking utensils. Reason (R): Aluminum forms a protective layer of aluminum oxide on its surface.
A.A is true but R is false.
B.Both A and R are true but R is NOT the correct explanation of A.
C.Both A and R are true and R is the correct explanation of A.
Explanation:
Aluminum is a highly reactive metal, yet it is widely used for cookware. This is because it rapidly reacts with atmospheric oxygen to form a thin, tough, and invisible layer of aluminum oxide (Al2O3) on its surface. This passivation layer prevents further corrosion and reaction with food.
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