Lead Definition and 291 Threads

Lead is a chemical element with the symbol Pb (from the Latin plumbum) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cut, lead is silvery with a hint of blue; it tarnishes to a dull gray color when exposed to air. Lead has the highest atomic number of any stable element and three of its isotopes are endpoints of major nuclear decay chains of heavier elements.
Lead is a relatively unreactive post-transition metal. Its weak metallic character is illustrated by its amphoteric nature; lead and lead oxides react with acids and bases, and it tends to form covalent bonds. Compounds of lead are usually found in the +2 oxidation state rather than the +4 state common with lighter members of the carbon group. Exceptions are mostly limited to organolead compounds. Like the lighter members of the group, lead tends to bond with itself; it can form chains and polyhedral structures.
Lead is easily extracted from its ores; prehistoric people in Western Asia knew of it. Galena is a principal ore of lead which often bears silver. Interest in silver helped initiate widespread extraction and use of lead in ancient Rome. Lead production declined after the fall of Rome and did not reach comparable levels until the Industrial Revolution. In 2014, the annual global production of lead was about ten million tonnes, over half of which was from recycling. Lead's high density, low melting point, ductility and relative inertness to oxidation make it useful. These properties, combined with its relative abundance and low cost, resulted in its extensive use in construction, plumbing, batteries, bullets and shot, weights, solders, pewters, fusible alloys, white paints, leaded gasoline, and radiation shielding.
In the late 19th century, lead's toxicity was recognized, and its use has since been phased out of many applications. However, many countries still allow the sale of products that expose humans to lead, including some types of paints and bullets. Lead is a neurotoxin that accumulates in soft tissues and bones; it damages the nervous system and interferes with the function of biological enzymes, causing neurological disorders, such as brain damage and behavioral problems.

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  1. C

    How does U(1) guage symmetry lead to Maxwell's equations?

    Here are some questions that have been puzzling me about symmetry and charge. Any answers to any of these questions would be very helpful. Thank you. What does U(1) gauge symmetry mean? Does anyone have a simple explanation? Can Maxwell's equations be derived from the premise of U(1)...
  2. P

    A 5cm long, 30g lead bullet strikes a wall at 27°C and melts on the wa

    Homework Statement A 5cm long, 30g lead bullet strikes a wall at 27°C and melts on the wall without splatter. How fast was it going? What is the force on the wall? If the wall is made of 1kg of marble, what temperature will it reach? Homework Equations I don't know how to find the...
  3. G

    Find the Lead Pursuit Line to Reach a Planet

    Suppose you are at a point (x0,y0) in space. There is a planet at position (x1,y1) orbiting in a circle a distance r away from the orbit center (x2,y2). The planet has constant angular velocity as it orbits. You move at a constant speed towards the planet, and want to move in a straight line...
  4. C

    Can supercharging of an engine ever lead to reduced power?

    Hi, I have decided to increase inlet T and P of a typical diesel engine (operatiing on dual air standard cycle). THeoretically if all other parameters r same, I have observed that t2 (temp at the end of compression) and p2 increases, but t3 (temp at the end of constant volume heating) and...
  5. P

    What should be molten Lead Fluoride or Crayolite Contained In? (Best Crucible)

    Hello, I am willing to do some experiments with molten Lead Fluoride and Crayolite in an electric muffle furnace, but I am not sure what type of crucible to use? Platinum Crucibles are way too expensive and I am assuming Alumina Crucible is not suitable... so, are there any other...
  6. J

    Heating Mercury Affecting Floating Lead

    Homework Statement A flat, uniform cylinder of lead floats in mercury at 0 degrees Celsius. Will the lead float higher or lower then the mercury temperature is raised? Homework Equations None. The Attempt at a Solution Since the mercury is heated, then the density will be lower...
  7. 1

    Why being too logical will lead to failing.

    True or False: "The moon has no atmosphere because we never see any clouds on the moon." Apparently, "The moon has no atmosphere because we never see any clouds" and "We never see any clouds on the moon because it has no atmosphere" are logically equivalent statements to the layman...
  8. A

    Why should radiation lead to loss in mass @ Black holes?

    According to theory of black hole radiation, black holes are expected to emit a thermal spectrum of radiation, and thereby loss mass, owing to the E=mc2 equation. Well, everything was clear to me till I got to the last point. why should there be loss only in mass?? couldn't the mass be same and...
  9. I

    One mole of Lead contains how many atoms

    How many atoms are in one mole of the element Lead(Pb) -Intrepid Elder
  10. T

    Where would the observation of a static Universe have lead us?

    Had our observations shown shown that the Universe was not expanding, and was instead static, where would that have lead us as far as Cosmology is concerned?
  11. I_am_learning

    What is the impact of long-term storage on sealed lead acid batteries?

    I am offered Sealed Lead acid batteries at heavy discount (half the price) at local Sale. But they were manufactured some 5 years back. How much damage does long storage do to them? They have never been touched. Just bought 5 years back, and stored.
  12. B

    Why does current lead the voltage in capacitor?

    We discussed this manner in terms of inductor, not so long ago. I fully understood from many posts provided why does it lag. I mean, not everything can be fully understood but I got a good intuition about it. Question arose not so long ago, and I couldn't find anything good on the...
  13. khurram usman

    How do lead batteries (rechargeable) supply both AC and DC power?

    lead battery(rechargeable)...? i was just wondering that the common lead batteries (the ones used in cars) supply us AC or DC? i saw a battery attached to a UPS and it steps up the 12V to 240V. so what i concluded was that it must give us AC. but how does it supply AC? i mean its positive and...
  14. O

    Lead Block inside 52' US-type Trailer Experiement

    Can someone calculate the weight of the object and what would most likely happen in the following experiment that I have always been curious about: Imagine you have a brand new 52-foot standard refrigerated cargo trailer mounted on a brand new standard heavy duty sleep cab tractor (i.e., an...
  15. T

    Does doubling the sum of prime factors always lead to 16?

    Here is the process: For example, take 28. Its prime factors (taken with multiplicity) are 2, 2, and 7. The sum of these is 11. Double it and you get 22. So, the sum of prime factors of 28 multiplied by 2 is 22. Repeat this process until you reach a loop or a stable number. For 28, if you...
  16. reddvoid

    Is Direct Rectification Suitable for Charging Lead-Acid Batteries?

    I want to charge a led-acid battery it needs 12V DC 1.i have transformer to convert 220V AC to 12V AC after that can i give 12V AC to bridge rectifier and from bridge rectifier to battery terminals directly or should i use a filter to remove the fluctuations in DC ? 2. what should be the...
  17. Redbelly98

    Lifetime of rechargeable battery (sealed lead acid)

    I have a cordless electric lawnmower that runs on sealed lead acid batteries. It is on it's second battery, which has noticeable degraded performance and will need replacing soon. My question is why the original battery, which was rated at 17 Amp-hours, lasted twice as long as this second...
  18. C

    Melting point of lead at 100atm

    Homework Statement Homework Equations use clausius-clapeyron equation: \frac{dp}{dt} = \frac{L}{T(V_{2}-V_{1})} which can be rearranged (i think) in the following: p = p_{0}+\frac{L}{\Delta V}ln(\frac{T}{T_{0}}) The Attempt at a Solution so using the above equation i solved...
  19. F

    Car things (Why does lead increase the octane rating)?

    Hey guys and girls The first thing I should probably ask is why do fuels (Hydrocarbons) spontaneously ignite when they are compressed, this seems rather strange to my brain in fact it makes my brain feel like it's having a meltdown (if you have ever had that feeling). The whole idea confuses...
  20. E

    Why does a lead acid battery spark when connecting to opposite terminals

    Sorry about the intrusion as I really don't belong here as I have absolutely no background in physics but I have a couple of questions regarding lead acid batteries that I have been unable to find answers to on the internet. First question - why does a battery spark/arc when the negative is...
  21. Astronuc

    News Lead presidential candidate - in 2032

    I hope so. Teen who challenged Bachmann to Constitution showdown is running for class president http://news.yahoo.com/s/yblog_thelookout/20110516/ts_yblog_thelookout/teen-who-challenged-bachmann-to-constitution-showdown-is-running-for-class-president There is hope for this country. We...
  22. P

    News Will protests in the middle east lead to any real change?

    What do you think about this? Are all these uprisings a sign that Muslims are ready for self-determination and will finally enter the world stage, or is this just an opportunity for the next round of corrupt politicians and dictators to grab power? Is democracy even possible in the Muslim world...
  23. A

    Solving for Melting Ice: 500g Lead & -10C Ice Block

    Homework Statement a 500 g lead mass is heated to 150 C and placed on a block of ice at -10 C. how much ice, if any will melt? 52 kg = block of ice Homework Equations The Attempt at a Solution i didint know where to start so i did qmcdeltaT + qmcdeltaT = 0, and i failed at it i...
  24. P

    Elastic collision of an alpha particla and Lead

    Homework Statement An a particle of mass 6.6 x 10-27 kg came closest to an atom of lead with a distance of 4.8 x 10-14 m. At what velocity will the a particle rebound directly away if the collision is totally elastic? Mass of the Alpha Particle - 6.6 x 10^-27 kg Alpha particles are...
  25. S

    How does asthma lead to cyanosis?

    As title suggest. Thanks :smile:
  26. D

    How does a gauge field lead to charge superselection?

    How does the electromagnetic gauge field lead to charge superselection and why does this fail when the symmetry is broken as e.g. in superconductors?
  27. I

    Thermal Expansion of lead rod question

    A lead rod and a common glass rod both have the same length when at 21.0° C. The lead rod is heated to 50.0° C. To what temperature must the glass rod be heated so that they are again at the same length? I did this: L = a*L0*T a (thermal expansion) of lead = (29e-6) a (thermal expansion) of...
  28. J

    Calculating Speed of Lead Bullet on Steel Sheet

    Homework Statement A lead bullet at 320K is stopped by a sheet of steel so that it reaches its melting point of 600K and completely melts If 80% of the k.e of the bullet is converted into internal energy calculate the speed with which the bullet hits the stee sheet. Homework Equations...
  29. M

    Why Does the Charge of a Lead Nucleus Affect Electric Field Calculation?

    Homework Statement The nucleus of a lead atom has a charge of 82 protons a. what are the direction and magnitude of the electric field at 1.0x10^-10 m from the nucleus? Homework Equations E=Kq/r^2The Attempt at a Solution I did E= ((9 x10^9)(1.6X10^-19)^82)/ (1.0x10^-10)^2 but when I...
  30. M

    Help to prove that an interval will lead to positive functions?

    Homework Statement Let f be continuous at c and f(c)>0. Prove that there is an open interval (a,b) centered at c such that f(x)>0 for all x that are elements of (a,b) Homework Equations we are supposed to use the sign preserving property?? The Attempt at a Solution I tried...
  31. B

    Clausius Clapeyron Equation of lead

    Homework Statement When lead is melted at atmospheric pressure the melting point is 327.0 degrees C, the density decreases from 1.101 x 10^4 to 1.065 x 10^4 kg/m^3 and the latent heat is 24.5 kJ/kg. Estimate the melting point of lead at a pressure of 100 atm. Homework Equations...
  32. H

    Parameters for Root Locus Method using Lead Compensator

    Hi everyone, I would please like some suggestions regarding where my error is, designing a lead compensator with the root locus method for a unity feedback control system where G = [12.5] / [2.5 1 2500]. I want to set the overshoot zeta = 0.5 for an overshoot of 16%, and settling time Ts =...
  33. S

    Why does vasodilation in periphery lead to reduction in blood pressure?

    Hello everyone, Ok generally what do they mean when they say vasodilation in periphery lead to reduction in blood pressure? Do I have to think of this as expanding the size of a fluid filled container so less fluid splashes againts the walls reducing pressure. Or do I have to think of this...
  34. D

    Lead screw and frame calculations

    Hi I am new to the design game as it where and I have scoured books and the internet looking for calcs, examples, help with a design I am putting together which involves raising and lowering a heavy object using a lead screw. I know its not strictly CNC stuff but I believe someone may be able...
  35. L

    Why lead can be used for protection ?

    Hi all, anybody knows why x-ray cannot penetrate into a sheet of lead paper deeply? Do only the big amount of electrons in lead atoms diffract the x-ray, or the protons in the atoms also contribute the diffraction ? Thank you for your time!
  36. L

    What's the Difference Between Ground Lead Screws and Lead Screws?

    What's ground lead screws ? What's the differences between the ground lead screws and lead screws ?
  37. H

    Why is it harder to start a car battery in winter?

    Homework Statement Why is it harder to start a battery in winter rather then summer? Homework Equations Nerst Equation Ecell = Ecell - RT/zf(lnQ) The Attempt at a Solution Isn't the lead sulfate bettery unique such that the electroyte for the anode and cathode is the same...
  38. R

    Dropping voltage (variable) of a sealed lead acid battery

    Hi, firstly apologies for what might seem like a 'basic' question, but I've been trying to work this out for a while. I have a sealed lead acid (SLA) battery - 6V 4AH. I would like to use this battery to power a 4V coil (for a display) - that is capable of (potentially) drawing the full...
  39. L

    Lead acid battery experiment reaction

    My set up was simply putting two lead plates into a beaker of sulphuric acid, then connect the lead plates to a power supply. What is the reaction for charging and discharging the cell? All equations I could found contain lead (IV) oxide... Is the reactions of my set up differ from a real...
  40. L

    Calculating Final Temperature of Lead Bullet

    Homework Statement A 5 g lead bullet moving at 343 m/s is stopped in a block of wood. All of the kinetic energy goes into heat energy added to the bullet. The initial temperature of the bullet is 24 degrees C. What is the final temperature of the bullet in degrees C? (cPb = 0.128 kJ/kg . K...
  41. G

    Calculating the Minimum Proton Speed Near a Lead Nucleus

    1. Predict the minumum speed of a 20.0MeV proton as it passes within 1.0x10^-13 meters of a lead nucleus having 82 protons. (Note: 1eV = 1.6x10^-19 Joules) 2. How do I start off? 3. All i can think of is to get a charge for the lead nucleus by using q=ne which is the number of...
  42. C

    Use dimensional analysis to show that increase in g due to lead

    Homework Statement A clock is placed on a floor covered with lead density \rho and thickness d. Use dimensional analysis to show that increase in gravitational field strength at the clock dueo to the layer of lead is proportional to Gd\rhoHomework Equations The Attempt at a Solution to show...
  43. A

    Lead/Lag compensator - lead and lag time to pole and zero locations

    Hi, I am having difficulty understanding how to convert pole and zero locations of a lead lag compensator into lead and lag time and vise versa. I have a digital lead and lag compensator which requests: gain, lead time (min) and lag time (min). However i have the gain zeros and poles of...
  44. X

    How Do You Calculate Lead Time for a Moving Target?

    Moving Target Lead Time ?? I am new to the forum...so I thought I would start with a simple question.. How do you figure up the lead time on a moving target Example 1.Target is moving from right to left @ 3.0 fps 2.Target is @ 60 ft out 3. Projectile is shot @ target @ 100...
  45. Chi Meson

    Kids' Jewelry Recalled Due to Cadmium

    Jewelry for kids! Guess where it was made? http://www.nytimes.com/aponline/2010/01/29/health/AP-US-Cadmium-Jewelry.html
  46. Wellesley

    Specific Heat molten lead Question

    Homework Statement If you pour 0.50 kg of molten lead at 328°C into 2.5 liters of water at 20°C, what will be the final temperatures of the water and the lead? The specific heat of (solid) lead has an average value of 3.4 X 10-2 kcal/kg • °C over the relevant temperature range.Homework...
  47. 8

    Half-Life of ^{208}_{82}Pb (alpha decay)

    Homework Statement Calculate the half life for alpha decay of ^{208}_{82}Pb (in years) Homework Equations gamow factor transmission probability coloumb potential The Attempt at a Solution...
  48. F

    Pressure and Displacement sound waves. Pressure always lead?

    A sound wave can be interpreted in any of four ways. Two of those involve the correspondence between (1)displacement and position and (2)pressure and position. [By "position" here I refer to the distance from the source. Positive refers to going away from the source.] These waves are 90...
  49. I

    Melting Lead in a Kiln: How Long Will it Take?

    Homework Statement A girl wishes to make a lead casting of an object which will require 2kg of melted lead. if the lead was stored in her basement at approximately 55 degrees F, and it is melted to a 1/4" thick steel pot of approximate cross sectional area of 12in^2, how long will it take...
  50. J

    Finding the distance of a gamma ray travels in lead

    Homework Statement The ‘half-thickness’ tells us the thickness of a given material needed to absorb half the incident photons from a particular source. Find the average distance of a gamma ray in lead before its first collision. I have a value for the half thickness (and equivalent half...
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