Which compound is an exception to the octet rule? h2o hcl ccl4 clf3

is an exception to the octet rule.

Explanation: Octet rule is general rule for most of the atoms which says that the atoms must have 8 electrons in their valence shell in order to be stable. For this they can gain, loose of share the electrons from the other elements.

The valence electrons can be determined by the lewis dot structures. Lewis dot structures are the structures in which the valence electrons around the nucleus of an element are shown.

For the given compounds, only one compound do not follow octet rule which is

In the given compound, the octet of all the 3 fluorine atoms are complete but chlorine has 10 electrons around it which is not followed by octet rule.

part 1: the half-life of the element is 22 years.

part 2: it will take 132.02 year for the sample to decay from 308.0 g to 4.8125 g.

explanation:

part 1: there are two ways to determine the half life time.

first way: the half life time can be determined directly from its definition as it is the time required for the sample to decay to its half concentration.

from the data the initial concentration was 45.0 g and decayed to its half value (22.5 g) in 22.0 years.

second way: the radio active decay is considered first order reaction so we can use the laws of first order reactions.

k = (1/t) ln (a/a-x), where k is the rate constant of the reaction,

t is the time of the reaction

a is the initial concentration of the reactant

a-x is the remaining concentration at time (t)

a = 45.0 g the initial concentration at t = 0 year.

at t = 22 year, a-x = 22.5 g

then k = (1/22 year) ln (45.0 g/ 22.5 g) = 0.0315 year-1.

the half-life time (t1/2) = ln 2/ k = 0.693/ k =0.693/ 0.0315 = 22 years.

part 2:

using the same law k = (1/t) ln (a/a-x),

using the given data; a = 308.0 g and a-x = 4.8125 g and the calculated k from the part 1 (k = 0.0315 year-1)

t = (1/k) ln (a/a-x) = (1/0.0315) ln (308.0/ 4.8125) = 132.02 years

c is the answer because when something is left after something evaporates that shows the chemical change.