Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: kanefears on December 08, 2010, 08:29:36 PM

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I have no Idea what to do. I was absent, and didn't have time to ask the teacher last week. Any help would be appreciated.

First find out what the symbols represent. They will be needed to write the nuclear reaction below.

Start by reading these;
 Alpha decay (http://en.wikipedia.org/wiki/Alpha_decay)
 Beta decay (http://en.wikipedia.org/wiki/Beta_decay)
 Gamma decay (http://en.wikipedia.org/wiki/Gamma_ray)

Thankfully, you were absent for a very simple topic.
In the format of superscript, subscript, and particle. We are looking at the nucleus of an atom, so for now, let's ignore the electrons in the shells
The format for all nuclear equations is that the superscript is the atomic mass  the number of protons + number of neutrons.
The subscript is the charge of the particles, in "elementary charges"  a proton is +1, a neutron is 0 , and there will be some particles with a 1, which are essentially electrons, even if we don't want to think of them that way.
The first part, then, is thus:
5.) Atomic mass of 1, charge of zero. That means that it is a particle with mass and no charge...and its symbol is little n . That would make sense that it is a neutron, then, right?
6.) Atomic mass of zero, a charge of negative 1. What particle, do we know of, that has no mass, and a negative one charge?
7.) Atomic mass of zero, a charge of positive 2. What nucleus has 2 positive charges, with mass? And a symbol He....what do you know with the symbol He, and a +2 nuclear charge.
8.) Looks much like number 7, but this time, it is symbolized by the greek letter alpha. Well, if it walks like a duck, it quacks like a duck, is it a duck? Yes  it is exactly the same particle as in number 7, except that it saves us a syllable, and doesn't look like its chemically interacting.
Nuclear equations require 2 things: a knowledge of basic math, and standard tables that tells us how these things break down (that's what they are doing).
Let's look at number 1:
231,91 Pa is what? The 91 in the bottom tells us the number of positive charges  the number of protons in the nucleus. What element is number 91? It is Protactinium, with a Wiki page here (http://en.wikipedia.org/wiki/Protactinium).
The 231 tells us that the isotope has a mass of 231 AMUs  which we know decays by alpha emission (see the wiki page).
231,91 Pa > 4,2 alpha + x,y ?
Laws of conservation of mass and charge apply  the numbers on the left must be the same as the numbers on the right.
Let's look at the top numbers  the mass.
231 = 4 + x
x = 237
Let's look at the bottom numbers  the charges
91 = 2 + y
y = 89
237,89 is given by what nucleus? Well, th 89 tells us that it is Actinium: http://en.wikipedia.org/wiki/Actinium . So, Actinium, with a mass of 237 is symbolized by
237,89 Ac (237 on top, 89 on bottom  no dash, it's not a math equation) would be that answer. Do the rest here, and we'll look it over.