Atomic Definition and 853 Threads

The relative abundance of various isotopes of silicon is as Si(28) = 92.25%, Si(29) = 4.65% and Si(30) = 3.10 % . Calculate the average atomic mass of Silicon. Ans : 28.11 u Attempt. : I don't know how to start this problem .

Homework Statement This is the statement out of a paper: Slurry 10 grams of ZnS with 3mL of .2N Cu(CH3COO)2 solution (corresponding to 0.6 atom % Cu) and 1.7 mL of .2N NH4Cl solution (corresponding to 0.34 atom % Cl) So my question is how did they calculate the .6 at. % and .34 at. %...

Homework Statement The hydrogen electron de-excites from its 3rd excited state, which are the true and false statements for it. 1. It emits radiation giving lines in Lymann, Balmer, Paschen series 2. It emits radiation of only UV and Visible region and not Infrared region 3. It emits radiation...

Homework Statement Suppose a nameless element (X) was found to occur in three different substances (A, B and C). The relative molecular masses of A, B, and C were found to be 25.80, 43.70 and 83.50 respectively, compared to an assigned value of exactly 2.00 for H2. Subsequently, these...

Imagine that we have got some vessel under standard temperature and pressure filled with atomic Hydrogen inside and the electrons of these atoms have got the same spin and therefore they cannot join into Hydrogen molecules, so the process of recombination does not occur. Then we begin cooling...

Hi When I read "popular" papers on atomic clocks, many journalists write that the clock loses 1 second in XX million/billion years. But when I look at some professional papers, people talk about a fractional instability of e.g. 10-14t-1/2, the authors never use the former way of characterizing...

Homework Statement Hi I have a question regarding the force that it used in Optical Molasses. The force is generally given by F = \frac{\hbar k}{2} \frac{s_0}{1 + s_0+ (2\delta/\Gamma)^2} where s0 is the saturation parameter. The force saturates to F = \frac{\hbar k}{2} It is normally said...

Hello. How big is day – night speed variations for stationary atomic clock placed somewhere on equator? And what experiment can measure such variations?

My question is about generalization of most simple problem in semi-classical quantum optics. Composite system of two-level systems. single system's diagram: http://ars.sciencedirect.com/content/image/1-s2.0-S0030401807009777-gr1.jpg where atomic frequency: wab=wa - wa; probing frequency...

Pardon my ignorance please, but they never taught us about that in school. I've never seen any mention in any of the chemistry/physics/electronics textbooks that I've ever read about how the atomic numbers of each element were empirically found in the first place. I understand it has something...

hi everyone! does a general Rydberg-like formula exist to predict the emission spectrum wavelengths of any atom? if not, why?

what are atomic energy levels? are they different in principle to electron energy levels? how to visualize atomic energy levels in any substance (solid, liquid and gas) I have read that during the formation of bose einstein condensate all the atoms comes to ground level from high energy levels...

A sample of carbon tetrabromide CBr4 contains 96.38% bromine and 3.62% carbon by weight, using the atomic weight of C as 12amu, find the exact atomic weight of bromine

Hi, For single-electron atomic systems, the electron can be specified by four quantum numbers n, l, m_l, m_s (principal, orbital, z-orbital, z-spin). The orbital quantum numbers are well defined since the problem is spherically symmetric. However, for many-electron systems, the spherical...

Suppose I have two acids HX and HZ. Say X is smaller then Z in atomic size. So then one would think that HX would be a more stable molecule then HZ since X has a higher charge density then Z (Both have same electronegativity) . HZ being a weaker molecule would dissociate more rapidly. Now my TA...

I know that the shape of s orbital is sphere, p orbital is dumbbell shaped and d orbital is like a doughnut but why do these orbitals have these shapes why not some other shape.

Homework Statement Hi I have a question - it is not homework, but something I have thought about for a long time. I really can't come up with a solution to the problem, and it is driving me crazy. Here is the problem: Say I have a linearly polarized monochromatic wave incident on an...

I've attached a graph of the pair potential between Mg and O. The peak attractive force experienced between the atoms is 1.6 eV, or 10^-19 Joules. From F=ma, with an O mass of 2.66*10^-26 kg the acceleration experienced by the atom is about 9650000 m/s^2, or 9.65 nm/fs (nanometers per...

Homework Statement Two questions : 1. find the (mass) density of Sodium. Atomic weight: 22.9898. Crystal structure: bcc. a=4.23 angstrom (crystal constant). 2. Given the (mass) density of Aluminum : 2.7 g/cm^3. Atomic weight: 26.982. Find the number of atoms density (# of atoms per cm^{3})...

Homework Statement I am trying to use interatomic pair potentials to calculate forces from velocities, but I seem to arrive at ridiculous values. 2. Homework Equations (and 3. Solution attempt) Consider that I have a potential function where (r is distance, E is potential energy, Ang is...

What is differences between the definition of.. Nucleon number, atomic number, and mass number. Is there any differences as i knew that those three symbol is A. am I right?

Hello my name is Brendon. I'm a graphic designer currently studying an MA. My major project is based around Eames' Power of 10 film and more recently the Huang twins Scale of the Universe website. I'm trying to reproduce these ideas in print, using folding to represent the orders of...

Hi all, I am preparing for a job interview in some nuclear facility and have to refresh my knowledge about nuclear stuff. So I started reading the book of Lewis "Fundamentals of reactor physics". I got stuck at page 35, formula (2.24). Does anyone have a clue how to arrive at this equation...

On the part “(0.8022 x 11.009) + (0.1978 x W) = 10.81 amu (natural atomic weight),” how do I know what to multiply 0.1978 by if W is unknown? How did they arrive at 10.81?

Hi I am looking at strontium, and I wish to find the difference in energy between the 1S0-1P1 transition (~ 461nm) in Sr-88 and Sr-86. I don't need to calculate it, I need to look it up in a table. I thought that NIST would be helpful (http://physics.nist.gov/PhysRefData/ASD/lines_form.html)...

Homework Statement Although H-atom contains one electron yet we get a number of lines in the spectrum of Hydrogen. Why??

For physics between QM and String Theory I've heard a lot of different names. Quantum Electrodynamics seems to be the physics of the electron and the photon. Quantum Chromodynamics seems to be the physics of quarks. But High Energy/Nuclear/Particle Physics, Atomic physics, QFT, I don't...

Hi, I have been researching antennas all day but I can't figure out how specifically they work in that; they seem to oscillate AC through like a band-pass filter (LC circuit) to get a signal. I'm assuming there is some sort of current 'sloshing' in and out of the antenna as they do. Also that...

Hello PF. I thought this would be a good place to ask around for information pertaining to "where we are at" in controlled creation of ultra-cold environments for atoms; for example, how cold an environment can we actually make today, etc.? I am especially interested in the BEC phenomena. When I...

the product of velocity of an electron and the principal quantum number is independent of which variable ? options given : a) velocity b) principal quantum number c) speed of revolution d ) energy of electron I wrote c, is it correct ?

I studied it in a book that Rutherfords Atomic Model was Unsatisfactory bcz the revolving electrons in his model would lose energy.How would they lose energy as far as I know they are kept in rotation by the centripetal force and work done by centripetal force is 0.NO work done no energy...

I have recently started using an AFM machine, and have some issues with the way it saves the data. The people who maintain the machine haven't been very helpful with my concerns, so I'm hoping somebody here might be able to help me. I have been using Gwyddion to display the raw data images...

Homework Statement The uranium isotope 235U captures a neutron and undergoes fission to produce 93Rb and 141Cs. Calculate the energy released in this process. The nuclear masses of the relevant isotopes are 235U 235.0439u, 93Rb 92.9217u, 141Cs 140.9195u Homework Equations...

I'm currently reading about nuclear and particle physics in B.R.Martins 'An introduction to nuclear and particle physics'. In chapter 7.3 he introduces the shell model of the nucleus and draws an analogy to the periodic table and how we think of it being constructed of progressively placing...

Homework Statement Despite extensive searches of the web and my old honors freshman chem text, I have yet to find a kj /mol value for either the standard Gibbs' Free Energy (Delta-G-naught (298° K)) or standard ENTROPY (Delta-S-naught) for the ionization of gaseous ATOMIC Hydrogen (or for...

Homework Statement Argon (atomic weight 40) exists as a monatomic gas at room temperature and pressure. The density of liquid argon is 1784 kg m−3. (a) Calculate the atomic density (atoms m−3) in liquid argon. (b) Calculate the atomic density (atoms m−3) in gaseous argon at a pressure...

and nuclei are so small(on an atomic level!). is it that there are SO many atoms around and that thermal neutrons are still incredibly fast, that if there is a reflector surrounding(lets say we're talking about a critical mass of uranium and an uncontrolled chain reaction), that the neutron will...

Homework Statement In question 50 in this link: http://www.tarleton.edu/Faculty/alow/prob21.htm I was wondering how the numbers 4.00260 amu + 1.00867 amu – 2.01410 amu – 3.01605 amu been obtained? Thank you. Homework Equations The Attempt at a Solution

I'm a year 12 physics student and I have a keen interest in the inner workings of a magnet. I know that magnetic fields are created by the motion of charged bodies. 1. Is this somehow related to the how magnets create their fields, within their structure at an atomic level? I've heard that...

What state of matter are atomic particles be in? A friend of mine suggested they might be virtual particles.

It is well known that, "Neil bohr failed in his model in which he described an electron as a charged particle moving in well defined circular orbits about the nucleus." However he failed because of the two major reasons.. a) It didn't consider the wave nature of the electrons b) contradicts the...

I am terribly confused. I have always been hearing that in the hydrogen atom, 2s and 2p orbitals have the same energy. Similarly, the 3s, 3p and 3d orbitals have the same energies. This is also suggested by the hydrogen spectrum, my professor also believes the same, and I am unable to find...

Hiroshima "Little Boy" Atomic Bomb Physics Help I just wanted some feedback on a paper I just finished. Did I do everything correctly and does it make sense? It seems my data supports information I found online: "It contained 64 kg (140 lb) of uranium, of which less than a kilogram underwent...

Hi all, Can we use Gauss's law to find the electric field near an electron, or is Gauss's law invalid in atomic scales? I ask this basic question because I know nothing about Quantum physics.

Hi, Not sure how stupid my question might be. Could anyone please clarify me, why the atomic clock in a spaceship is taken as a reference while explaining a special theory of relativity?. I always wonder how 2 people one outside the spaceship and the other inside it feels about a time in...

Hey guys, I am thinking about world at small scale and world at larger scale. Why world is more chaos at smaller scale and why it is more smooth and uniform in larger scale?

Dear friend, I am getting confused in this question;what i learned till now is that number of proton+number of neutron=atomic mass. But while searching the net i got this equation atomic mass = mass a x fract a + mass b x fract b. can anyone tell me which is the correct (not approximate)...

When dissolved in water, which of the following ions will form stronger ion-dipole bonds with the water molecules? Li+ or Na+? Both have roughly the same charge... Na has greater radius, but I don't see why or how that has any bearing on the problem.

I'm having some troubles understanding the unit used in solid state physics. In a paper I read \Lambda a \sim 1 where \Lambda is a momentum cutoff and a is the lattice spacing of a crystal. Questions: 1) What kind of units are customarily used in solid state physics scientific...

Hi, long time user, first time poster. A while back someone posted a great question https://www.physicsforums.com/showthread.php?t=33584 To paraphrase, can you explain on a spin-by-spin level exactly how a 181* pulse is possible? You always hear this really intuitive explanation of...