Lead have:
82 electrons
82 protons
125 neutrons
Explanation:
The number of electrons and protons are given by the atomic number of the element.
Lead have 82 electrons and 82 protons.
The number of neutrons are given by the difference between the mass number and atomic number.
For lead number of neutrons = 207 - 82 = 125.
Learn more about:
particles in the atom
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Answer: To test the properties of the particles, Thomson placed two oppositely-charged electric plates around the cathode ray. The cathode ray was deflected away from the negatively-charged electric plate and towards the positively-charged plate. This indicated that the cathode ray was composed of negatively-charged particles.
Thomson also placed two magnets on either side of the tube, and observed that this magnetic field also deflected the cathode ray. The results of these experiments helped Thomson determine the mass-to-charge ratio of the cathode ray particles, which led to a fascinating discovery−-−minusthe mass of each particle was much, much smaller than that of any known atom. Thomson repeated his experiments using different metals as electrode materials, and found that the properties of the cathode ray remained constant no matter what cathode material they originated from. From this evidence, Thomson made the following conclusions:
The cathode ray is composed of negatively-charged particles.
The particles must exist as part of the atom, since the mass of each particle is only ~1/2000 the mass of a hydrogen atom.
These subatomic particles can be found within atoms of all elements.
While controversial at first, Thomson's discoveries were gradually accepted by scientists. Eventually, his cathode ray particles were given a more familiar name: electrons. The discovery of the electron disproved the part of Dalton's atomic theory that assumed atoms were indivisible. In order to account for the existence of the electrons, an entirely new atomic model was needed.
The answer is Make sure you are working with a properly balanced chemical equation.
Convert grams of the substance given in the problem to moles.
Construct two ratios - one from the problem and one from the chemical equation and set them equal. ...
Convert moles of the substance just solved for into grams. Step 1: Convert known reactant mass to moles. ...
Step 2: Use the mole ratio to find moles of other reactant. ...
Step 3: Convert moles of other reactant to mass. Balance the equation.
Convert units of a given substance to moles.
Using the mole ratio, calculate the moles of substance yielded by the reaction.
Convert moles of wanted substance to desired units.
The mass number goes on top, and the atomic number goes on bottom.
Therefore, the answer is C:
40
K
19
