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2.4 The Discovery of the Electron -- Part 2
As we discussed earlier, both particles have the same mass.
The mass of the protons is 1.67262 and the mass of the neutron is 1.67493 in SI units.
The mass of a rice grain is about the same as the mass of a protons.
The mass of electrons is less than 10 or amu.
The electron has a charge of -16 and the protons has a charge of +2.
There is no charge for the neutron.
Rice grain trons are usually present in equal numbers so matter is usually charge neutral.
When matter acquires charge imbalances, they usually equalize quickly.
The negative charge builds up on the clouds.
During electrical storms, there is an increase in charge imbalances.
A sample of matter composed of only protons or electrons would be unstable due to repulsive forces within it.
Matter is not that way.
The properties of protons, neu charge imbalance are summarized in Table 2.1.
There is a positive charge on the ground.
An atom with two protons in its nucleus is a helium atom, an atom with six protons in its nucleus is a carbon atom, and an atom with 92 protons in its nucleus is a uranium atom.
Evidence for the synthesis of additional elements is currently being considered, but the atomic numbers of known elements range from 1 to 118.
The elements are arranged so that they are in the same column.
The symbol for carbon is C, the symbol for He is C, and the symbol for U is U.
The atomic number and chemical symbol always go together.
This is another way of saying that the element is defined by the number of protons.
The English name of the element is what most chemical symbols are based on.
The symbol for sulfur is S, the symbol for oxygen is O, and the symbol for chlorine is Cl.
The symbol and atomic number represent each element.
There are elements in the same column.
Scientists give new elements names that reflect their properties.
The elements are named after figures from Greek or Roman mythology.
The places where they were discovered or where their discoverers were born are where europium, polonium, and berkelium are named.
Some elements have been named after scientists, for example, rutherfordium for Ernest Rutherford.
All elements have the same number of protons and neutrons, but they do not necessarily have the same number.
Each of the three types of neon atoms has a slightly different mass.
Some elements, such as beryllium and aluminum, have only one naturally occurring isotope, while other elements, such as neon and chlorine, have two or more.
The relative amount of different elements in a sample is constant.
In any natural sample of neon atoms, 90.48% of them are the isotope with 10 neutrons, 0.21% are the isotope with 11 neutrons, and 9.05% are the isotope with 12 neutrons.
Each element has its own abundance of isotopes.
Mass spectrometry has allowed accurate measurement of the natural abundance of isotopes for many elements.
For neon with 10 protons, the mass numbers of the three different naturally occurring isotopes are 20, 21, and 22, corresponding to 10, 11, and 12 neutrons.
If the atomic number is 10, the symbol must be Ne.
The mass numbers for the different isotopes are different, reflecting the different number of neutrons in each one.
The chemical symbol is followed by a dash and the mass number of the isotope.
All elements have the same number of protons, otherwise they would be different elements.
The chemical behavior of the different isotopes of an element is the same.
17 is the number of protons that chlorine has.
The number of protons is specified by the atomic number.
The number of protons and the number of neutrons are related.
The number of protons is indicated by 24 lower left.
The number of electrons is equal to the number of protons.
The number of neutrons is equal to the mass number minus the atomic number.
In many chemical reactions neutral Li atoms lose one electron 1e-2 to form Li+ ion.
The charge of an ion is shown in the upper right corner of the chemical symbol.
The Li + ion's charge is 1+ since it contains three protons and two electrons, and the 1 is usually dropped and the charge is written as simply +.
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