[owned123]

So i dropped one of my favourite classes to get into this class and i'm a little behind because i did it 3 days after school started.

Shes already given out a bunch of homework that i've been doing since 1:00

I've spent most of my weekend on it but still don't understand these are only a few of the questions that i really can't understand.




Here are some questions and help would be great.


How does bohrs atomic theory explain periodic trends?


From a representative element's position in the periodic table, how would you determine each of the following?
(a)number of protons
(b)Number on electrons
(c) number of valence electrons
(d)Number of occupied energy levels


Chemical Name and symbol corresponding too each of the thoertical descriptions
(a)11 protons and 10 electrons which i think is sodium (Na)
(b)18 electrons and a net charge of 3- magnesium?
(c)16 protons and 18 electrons

Determine the number of Protons electrons and neutrons isotopes
(a)Calcium-42
(b)strontium-90
(c)cesium-137
(d)iron-59
(e)sodium-24

Iodine-123 in the compound sodium iodide is a common radiosiotope for medical use

what does the difference suggest about the abundance of iodine-123 in an average sample of iodine atoms

[nj_bartel]

You need to show some work.

[owned123]

Well for this question
"From a representative element's position in the periodic table, how would you determine each of the following?
(a)number of protons
(b)Number on electrons
(c) number of valence electrons
(d)Number of occupied energy levels"


I knew protons are found using atomic number and electrons, valence are found using the group its in then subtracting by 10
and occupied i used my equation 2n^2 or however you do squared

[Yggdrasil]

I knew protons are found using atomic number and electrons, valence are found using the group its in then subtracting by 10
and occupied i used my equation 2n^2 or however you do squared

a,b) Correct.  Number of protons and number of electrons in an atom are equal to the element's atomic number. 

c,d) However, your answer for the number of valence electrons and number of occupied energy levels are incorrect.  There is any easy way of finding these: to find one, you look at which row the element sits, and for the other, you look at the column in which the element sits.  I'll leave it to you to figure out which one goes with which.

Chemical Name and symbol corresponding too each of the thoertical descriptions
(a)11 protons and 10 electrons which i think is sodium (Na)
(b)18 electrons and a net charge of 3- magnesium?
(c)16 protons and 18 electrons

a) 11 protons gives sodium, but Na is not correct.  You have to account for the fact that it is an ion (Na⁺).

b)  If an ion has 18 electrons, and a charge of -3, how many protons will it have?

[dabaichi]

Bohr's atomic model shows that the nucleus of the atom is positively charged with electrons surrounds it moving in orbits form. Every orbit has a new level of energy (quantum). This explains why the periods (rows) of the periodic table appears as such- because every row represent a new level of energy.

a) For increase in proton number, you count the element from left to right across every period.
b) Since neutral elements have the same number of protons to electrons, the explanation is the same for protons.
c) Valence electron is the number of electrons in the most outer shell. The column number is equal to the number of valence electron for most elements.

Chemical names:
a) 11 protons = atomic number 11 which is sodium (Na). But it has 10 electrons, which means it is oxidized to a cation Na+.
b) 18 electrons but with net charge of -3, this means it is reduced to an anion. To find the neutral element, you need to remove 3 electrons from it. So it has 15 electrons in neutral state. Atomic number 15 is element phosphorus (P).
c) 16 protons = atomic number 16 which is sulfur (S). It has 18 electrons which has a net charge of -2. So it is S2-.

Isotopes:
a) Calcium-42 has atomic number 20 which means it has 20 protons. To find the number of neutron, you subtract the mass of the element by the proton number. So in this case, 42-20= 22 which is the neutron number.
b) Sr-90, Z#(proton number)= 38, N# (neutron number)=52
c) Cs-137 Z#=55, N#=82
d) Fe-59 Z#=26, N#=33
e) Na-24 Z#=11, N#=13