Atomic Definition and 875 Threads

1 u = 1/12 of the mass of a neutral carbon atom with nuclear charge 6 and mass number 12, 1 u = 1/12 * 12.000000 /NA * 0.001 where NA is avogadro's number. I wonder is it that the scientists purposely make one mole of carbon-12 to be just 12.00000g? I want to ask is it when the...

I am doing some research on atomic clocks. From what I have read, I understand that in Rb atomic clocks you: -optically pump a cell of Rb, so that the electrons are all in a single hyperfine state -subject the cell to microwaves of appropriate frequency, so that the electrons will be...

A nuclear warhead for example doesn't seem to take a lot of energy to make, however it outputs massive amounts of energy in an instant. Why isn't this more energy out than in and why doesn't it break the law of conservation of energy? I think the answer is going to have something to do with...

Homework Statement Suppose that a human head is a sphere with the bone thickness 10% of the radius of the head. Find the fraction of the volume of the head occupied by the brain. Make a similar estimate (forget about factors of pi) in the N-dimensional space (d = N) in the limit N ->...

my question is : How would you make a 1, 3, 5, 7ppm solution from a 100ppm solution? do i just just this formula: C1V1 = C2V2 to calculate the amount i need? for example, for 5ppm solution => (5ppm) V1 = (100ppm)V2 so for V1, I just choose my final volume to be whatever i like... like...

all says electrons rounds the nucleus and revolves in its own axis if so in which direction electrons rounds the nucleus?

i have a big problem while i m trying to measure Cr with flame with Aanalyst 200 i m following the guidelines of perkin elmer. i m using a rich yello flame 4.5/10. i have made some standards 0.2, 1,2,4 with 0.2% nitric acid. i m doing calibration and when i finish i have noticed that the...

Ok, I just posted this in the advanced forum, but looking at some of the topics on there my question might belong in here instead.. I understand Rutherford proposed that electrons orbit around a central nucleus. However, since accelerating charges produce electromagnetic radiation, the...

I understand Rutherford proposed that electrons orbit around a central nucleus. However, since accelerating charges produce electromagnetic radiation, the orbiting electron should lose energy via E&M and spiral into the nucleus. But my question is: How do I calculate the time it takes for the...

Homework Statement The ground state electron configuration for phosphorus, which has 15 electrons, is 1s^2 2s^2 2p^6 3s^1 3p^4 1s^2 2s^2 2p^6 3s^2 3p^3 1s^2 2s^2 2p^6 3s^2 3d^3 1s^2 2s^2 2p^6 3s^1 3d^4 1s^2 2s^2 2p^6 3p^2 3d^3 Homework Equations The Attempt at a Solution...

Hello all! I realize these questions may have been more appropriately posted in another forum, however for their application I will use interstellar space. 1st: As I just read a few threads down, solar wind consists of protons and electrons, overall the charge of the sun (or any mass)...

Homework Statement Please help me calculate the center of mass of the polymer (radius) from atomic coordinates (more than 2000) given in Armstrongs. Can anyone help with the formula? I need to calculate the radius of gyration of the polymer. Thanks. Homework Equations The Attempt...

On the P.T.E., the atomic mass number of an element gives the number of protons and neutrons in its nucleus, ie. the number of particles in its nucleus. But this number also gives that particular elements molar mass, correct? eg. For carbon, it has 12 particles in its nucleus, and its molar mass...

i'd like to know what is the number of atoms per unit length for an atomic chain in the [1 1 1] direction of a BCC structure. i can figure out the unit length, however I'm not sure how many atoms to use. Is it 1/8+1/8+1? That means 1/8s for the two corner atoms and 1 atom for the middle? or...

The Little Boy bomb dropped on Hiroshima was very inefficient in terms of the amount of uranium fissioned. My questions are: What happened to the unreacted uranium and does it still pose a problem? I'm sure for most of you on this site this is an extremely easy question, but I am new to this and...

Big Question! In my chem class the teacher doesn't explain very much so I decided to see if this site may help. Ok, so my question is: The atomic mass of an element X is 46.80. A 35.78 gram sample of X combines with 84.10 grams of another element Y, to form the compound XY. Calculate the atomic...

Hi I was wondering if anyone could give me info about atomic electric dipole moment at a very fundamental level (fenomenological, basic quantum), I do not seem to find it when I google =( My Aim is just to understand van der Waals binding in solids a little bit more.

I need help with these two questions: 1. Electron diffraction can be used to investigate both the arrangement of atoms and the dimensions of nuclei. Explain how changing the energy of the electrons can be used to achieve this. And... 2. Uranium has atomic number 92. Two of its common...

https://www.physicsforums.com/showpost.php?p=899393&postcount=4 describes why photons are slower in some medium. After reading it, I've few more questions: When a photon hits an electron, if it absorbs the photon and reemits, here's my questions: 1. How does refraction possible? The...

i heard that there is an idea (i don't know if it's true) that we can make ANY ELEMENT radioactive! and i thought "wtf"!

Hello all, I'm having a little trouble researching this as I'm not sure what the exact field of study is called, googling Atomic Vibration doesn't come up with much. Basically I am looking to disprove a theory (with hard science) that thoughts can affect the crystalisation of water. The...

I can't understand how both the atomic weight of one atom of an element and the weight in grams of a mole of that element are the exact same thing. For example helium has an atomic mass of 4.0026. That was obtained by adding the amount of protons and neutrons in a helium atom together. On...

How to explain transmission, reflexion, refraction and diffraction at a atomic level. For example: 1 - how does light passes through a transparent material? 2 - what happens in the boundary of separation of two materials for light to be: partially reflected, partially refracted ad partially...

Why are the atomic weights of elements not integers and how many grams would there be in 1 amu (atomic mass unit) of a material? I know these are trivial questions but it's been a long time since I left school! Thanks. -SK

Oh god, please help... 1. Describe the attraction forces between atomic solids. Upon what factors do the strength of these forces depend? 2.Which of the noble gases would have the highest melting point? Why? :blushing:.. I'm not very good at chemistry

Kindly give me a link to some place I can study about Atomic Structure and Periodicity/Classification for IIT-JEE

Homework Statement Find the wavelength of the sodium transition 3p^{1},^{2}P -> 3s^{1},^{2}S Homework Equations E_{n,l} = -\frac{hcR}{(n - d(n,l))^{2}} d(3,s) = 1.374 d(3,p) = 0.884 \lambda = \frac{\hbar c}{\Delta E} The Attempt at a Solution Plugging the numbers in ain't...

Homework Statement In Clark's tables, the atomic masses of various isotopes are given which are decimal form. Are these experimentally obtained masses? Moreover, while writing nuclear reactions we do not use these, instead they are represented as integers. Is it just for convenience or is...

Can anybody tell me why atomic decays are usually only through electric dipole transitions, while nuclear decay often shows many different multipoles? i think that the transition rate for electric dipole transitions is much larger than for magnetic ones, but that doesn't really explain it. would...

Homework Statement I am having some trouble with this one, Suppose an atomic bomb was exploded in a box that was strong enough to contain all the energy released by the bomb. After the explosion the box would weigh: a) more than before the explosion b) less than before c) no change...

Is there a particular reason why the probability density distribution function of atomic orbitals bears a similarity to the modes on a circular membrane? Is this just a coincidence? Is it not actually that similar?

Hello, I'm Eddie and this is my first post here. I'm almost a Junior in college going for a B.S. In chemistry but I must say that time dilation is one of the most interesting things in science. I was wondering if anyone has actual figures with regards to the difference in time between a...

Lets say that you took a Hydrogen Atom and expanded it to the size of let's say a basketball. I am not just saying the atom itself but the nucleus. If the nucleus expanded to the size of a basketball; how would the electron size up porportionally. Now keeping it all porportional what would the...

Homework Statement What is the de Broglie wavelength of an ^{14}\mbox{N} atom that has been laser cooled to a temperature of T=77K. The Attempt at a Solution This is a trivial problem, and I can do the physics... But how do I calculate the mass of ^{14}\mbox{N}? My chemistry is obviously...

Are integers such as n=1,2,3 etc in Bohr's atomic theory, exactly whole numbers or just very close to being whole numbers?

It's interesting that TV series these days are adding suspense to the show by adding the threat of atomic bombs and nuclear explosions. But have the writers done their homework? Is this stuff anywhere near plausible? I'd like to know other peoples' opinions. Example 1, "24" An unmanned...

Hi Physics Forum. I've a question and hope you guys could give me some advice. I've been offered the chance to pursue a Phd in the field of atomic physics. The project involves investigating the spectral properties of Helium atoms using semiclassical techniques. It seems the project will be...

1: Why are the elements of a basis set taken to be orthogonal? But in real sense atomic orbitals do overlap.

As I understand it, electrons orbit a nucleus in a sort of spherical "cloud", kept in tow by said nucleus' protons. However, when two or more atoms combine, what keeps the negative charge in the electron "clouds" from simply pushing them apart?

Homework Statement Hi, I'd doing question 1 of the attached sheet and just wondered if someone could help me out. I'm a bit unsure of my calculus and need it reviewed, alsoam not entirely sure how to break down my workings (using the supplied equations in the hint) to find C. So any input...

Homework Statement A molecule with angular momentum L and moment of inertia I has a rotational energy that can be written as E=\frac{L^2}{2I}. Assuming that angular momentum is quantized according to Bohr's rule L = n\hbar, find the wavelength of the photons emitted in the n=2 to n=1...

Homework Statement To study the structure of the lead nucleus, electrons are fired at a lead target. Some of the electrons actually enter the nuclei of the target, and the deflection of these electrons is measured. The deflection is caused by the charge of the nucleus, which is distributed...

I recently purchased a new book that reviews most historical models of the atomic nucleus: http://www.brownstationers.com/BookItem.aspx?item=9783540285694 This is the only book on this subject in the past 40+ years that gives positive review (well--any review actually) for the 1965 Linus...

Homework Statement That's the problem statement (above). I basically need help knowing which fields to cover while talking about said topic in a 5-minute oral presentation. Pretty much, what I need to talk about (specifically). Homework Equations None. The Attempt at a Solution...

I came across this looking for something else. I'm curious as to what, if any, objective reality is associated with it. http://www.rense.com/general3/8000.htm

Homework Statement which of the following mass ration is ture? Mass of alpha-particles: mass of neutrons : mass of gamma- rays equal to A. 4 : 1 : 0 B. 4 : 0 : 1 C. 1 : 1 : 1 D. 1 : 1 :0 Homework Equations nil The Attempt at a Solution I thought it's D but the...

Homework Statement 1. Which of the following statements is / are not correct? (1) In fission, two large fragments of equal masses are produced from a nuclide. (2) Natually occurring elements perform fission spontaneously. (3) 2 H2O --> 2H2 + O2 involves nuclear fission. Homework...

Homework Statement Which of the following reactions will release large amount of energy (1) Nuclear fusion (2) alpha - decay (3) Nuclear fission (4) gamma - decay two of the options are: B (1) and (3) only D (1), (2), (3), (4) Homework Equations none The Attempt at a...

I spent my Thanksgiving trying to solve my homework and I will need some help: 1)For fixed electron energy ,the orbital quantum number l is limited to n-1.We can obtain this result from a semiclassical argument using the fact that the larges angular momentum describes circular orbits,where...

which atom has a larger atomic radius: K+ or Ar ?