Periodic table is the representation of elements in an order
The history of periodic table can be summarized as
a) 1829 : Johann Dobereiner proposed the triad rule. According to him we can classify the elements in a triad where the atomic mass of middle element is average of atomic mass of the near by two atoms.
For example : Li, Na and K is a triad. Where atomic mass of Na is average of atomic mass of K
atomic mass of Na = 7+ 39 / 2 = 23
However, with the further discovery of elements the law was rejected.
b) 1864 : John Newland proposed the law of octave. According to him we can arrange the elements in a set of seven elements where the property of second set of seven elements will resemble the properties of first of seven elements or property will be repeated after seven elements. This was also rejected due to its limited applicability.
c) Meyer : He arranged some 28 elements into six different families based on their atomic masses. The members of each familiy shared some common properties.
d) 1869 : Mendleev : He actually developed a periodic table based on atomic mass of elements. He arranged the elements into groups and periods. He even left space for some undiscovered elements, which were later on discovered.
e) 1916 : Henry Moseley : He finally arranged elements based on their atomic number based on X-ray studies. He proposed the modern periodic law that the periodic properties of elements are due to atomic number of elements.
Answer is the mass of the atom. Protons + neutrons= mass
Let's say you have oxygen with a mass of 16.
Oxygen has 8 protons
To find neutrons subtract 16-8= 8
So it would also be 8 neutrons.
Example of how to find mass if you know protons + neutrons:
Sodium has 11 protons and 12 neutrons. Add the protons and neutrons
11 + 12= 23
Mass is 23
Answer:
I don't think so
Explanation:
The equation doesn't look balanced
Answer:
In strict SI units (highly recommended), express n in moles, R is the universal gas constant R=8.314Jmol−K , T is the temperature in Kelvins, and the volume V is in m3 . The resulting pressure P will be in Pa. R=0.082054L−atmmol−K , in which case the pressure is calculated in atm.
