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3 years ago

A radioactive nucleus alpha decays to yield a sodium-24 nucleus in 14.8 hours. What was the identity of the original nucleus?

Chemistry

1 answer:

Rudik [331]3 years ago

5 0

Answer:

2813Al

Explanation:

You know that alpha decay takes place when a α-particle is being ejected from the nucleus of a radioactive isotope.An

α-particle is simply the nucleus of a helium-4 atom. A helium-4 atom has a total of two protons and two neutrons in its nucleus, and two electrons surrounding that nucleus.

In that case, if a α-particle is the nucleus of a helium-4 atom, then it must have a mass number equal to 4, since it has two protons and two neutrons, and a net charge of (2+) since it no longer has the two electrons that the helium-4 atom has.

So, you know that an unknown radioactive isotope decays via alpha decay to yield a sodium-24 nucleus.

A sodium-24 nucleus contains 11 protons and 13 neutrons. This means that you can write

AZX→2411Na+42α

Here A and Z represent the unknown element's mass number and atomic number, respectively.

So, if you take into account the fact that mass number and atomic number must be conserved in a nuclear reaction, you can say that

A=24+4 and Z=11+2

The unknown isotope will thus have

{A=28Z=13

A quick look at the periodic table will show you that the element that has 13 protons in its nucleus is aluminum, Al. This means that you're dealing with aluminum-28, an isotope of aluminum that has 15 neutrons in its nucleus.

The complete nuclear equation will be

2813Al→2411Na+42α

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does the nitro group on the pyridine ring make the ring more electron rich or more electron deficient

Arte-miy333 [17]

Answer:

more electron deficient

Explanation:

The nitro group is an electron withdrawing group. It withdraws electrons from the pyridine ring by resonance.

This electron withdrawal by resonance makes the pyridine ring less electron rich or more electron deficient.

Hence, the nitro group makes the pyrinde ring more electron deficient

3 0

3 years ago

J. Explain how an atom's valence electron configuration determines its place on the periodic table.

Darya [45]

Answer:

Elements having same valence electrons are placed in same group.

Explanation:

First, let's start with some basic concepts of modern periodic table:

1. Modern Periodic table : It is the arrangement of element in the increasing order of their atomic numbers

The Modern periodic table is divided into Periods and groups .

Periods : These are the horizontal rows. There are seven periods in the periodic table . Period 1 has 2 element. Period two and three has 8 elements , period 4 and 5 have 18 elements and the period 6 and 7 have 32 elements.

Same period have same number of atomic orbital(Shell)

Group : The group is the vertical columns . There are 18 groups in the modern periodic table.Those element which have same group number will also have same number of electron in their outermost shell. The number of electron in the outermost shell determines the valency of the element.

So, elements showing same valency are placed in same group.

All alkali are place in group 1 and have 1 valance electron in the outermost shell

5 0

3 years ago

How many total moles of ions are released when the following sample dissolves completely in water? Enter your answer in scientif

Katena32 [7]

Answer: The number of moles of strontium bicarbonate is $7.5\times 10^{-9}mol$

Explanation:

Formula units are defined as lowest whole number ratio of ions in an ionic compound. It is calculate by multiplying the number of moles by Avogadro's number which is $6.022\times 10^{23}$

We are given:

Number of formula units of $Sr(HCO_3)_2=4.55\times 10^{15}$

As, $6.022\times 10^{23}$ number of formula units are contained in 1 mole of a substance.

So, $4.55\times 10^{15}$ number of formula units will be contained in = $\frac{1}{6.022\times 10^{23}}\times 4.55\times 10^{15}=7.5\times 10^{-9}mol$ of strontium bicarbonate.