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C1 - Principles of Chemistry
Atom = 3 subatomic particles
protons (found in nucleus with mass 1)
neutrons (found in nucleus with mass 1)
electrons (orbiting the nucleus with mass 1/1840)
Elements are made up of only one type of atom
The atomic number of the element in the periodic table tells us the number of protons and
electrons - this is the smaller number.
The number of neutrons = nucleon number - the atomic number
Gold (Au) - Nucleon number is 197 and atomic number is 79
- 197 - 79 = number of nucleons = 118
- Number of protons and electrons is 79.
Number of neutrons can change but the number of electrons and protons has to stay the
same. - Isotopes
eg: A sample of chlorine contains 75% Cl (nucleon number 35) and 25% Cl (nucleon number
37). What is its RAM (Relative Atomic Mass)?
Ans: (0.75x35)+(0.25x37)=35.5 (no units)
Balancing Equations - Same number of atoms of each element on both sides of a symbol
equations makes the equation balanced
H2SO4 + NaOH Na2SO4 +H2O
Left Side: H=3, S=1, O=5, Na=1 Right Side: H=2, S=1, O=5, Na=2
H and Na are not the same number.
So... H2SO4 + NaOH Na2SO4 +H2O = H2SO4 + 2NaOH Na2SO4 +2H2O
Relative Formula Mass of sulphuric acid (H2SO4)
RAM of each element of the compound = frequency of element x nucleon number (bigger
RAM of compound = RAM of each element added together
So H2SO4 =....
(2x1) + (32x1) + (16x4) = 98 (no units)