Chemistry, 09.10.2019 17:30 samy14

the elements in alkali metal and halogen groups of the periodic table are the most reactive since they only need to gain or lose one electron to become stable by filling their valence orbital. what happens to reactivity, moving down the column of a group?

a) reactivity stays the same because they are in the same group.
b) reactivity increases because the valence level is further from the nucleus of the atom.
c) reactivity decreases because the increased number of protons and electrons provides more stability.
eliminate
d) reactivity stays the same because the number of electrons needed to fill the valence orbital remains the same.

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Answer from: mahmudabiazp3ekot

Reactivity increases because the valence level is further from the nucleus of an atom.

Explanation:The reactivity of elements in the periodic table depends on the position of the element in the periodic table. The trend in the reactivity across the period and down the group depends on whether one is dealing with metallic elements or non-metallic elements.Reactivity of metals such as alkali metals and alkali-earth metals increases down the group as the number of energy levels increases making valence electrons to be further from the nucleus.Reactivity of non-metallic groups such as halogen decreases down the group as energy levels increase which reduces the nuclear attraction of the valence electrons to the nucleus.

Answer from: Quest

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

Answer from: Quest

You know how the first one if filled up like the objects do the same but with the other categories

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