Which of the following neutral atom configurations satisfies the octet rule? a. 1s2 2s2 2p6 3s2 3p6 b. 1s2 2s1 c. 1s2 2s2 3s2 3p4 d. 1s2 2s2 3s2 3p6 4s1 which group of atoms always has a complete octet, a full s and p orbital at the end of the configuration? a. alkaline earth metals, group 2a b. halogens, group 7a c. noble gases, group 8a d. transition metals a neutral atom of sodium (na) has 11 electrons and an electron configuration of 1s2 2s2 2p6 3s1. how will it ionize to achieve an octet in its valence shell? a. it will gain 7 electrons in the 3rd energy level to have a valance configuration of 3s2 3p6. b. it will lose 1 elecrtron for the 3rd energy level to have a valance configuration of 1s2 2s2 2p6 c. it will not ionize, it already has an octet of electrons in its valance shell.

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

explanation: