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# Chem. Section 1.

### Section 1- formulas and equations

atoms are made of? protons and neutrons are within the nucleus, and electrons surround the nucleus in orbitals.
What are electrons, protons and neutrons charge and relative mass? Electron- 1/200 relative mass, -1 charge. Proton- 1 relative mass, +1 charge Neutron- 1 relative mass, 0 charge
what is the mass number? the total number of neutrons plus electrons.
atomic number? the amount of protons in the nucleus. (also the same as the number of neutrons)
What are ions? Ions are elements with different numbers of protons and electrons. e.g Br - has a negative charge meaning it has one more electron than protons. e.g Mg 2+ has 2 fewer electrons than protons.
What are isotopes? Are atoms of the same element with different numbers of neutrons.
What is the relative atomic mass? is the average mass of an atom of an element on a scale of an atom of carbon-12 is 12.
what is the relative isotopic mass? is the average mass of an atom of an isotope of an element on a scale of an atom of carbon-12 is 12.
what is the relative molecular mass? is the average mass of a molecule on a scale where an atom of carbon-12 is 12.
What is the Molar mass? is just the same as the relative molecule mass.
how do you work out the molar mass? number of moles= mass of substance/molar mass
how do you work out how many moles is in a solution? number of moles= concentration x volume (in dm3)
how many dm3 in a cm? dm3= 1000 cm
what is parts per million? ppm- used for very small amounts e.g % of gasses, like there is 0.000 009% xenon in the atmosphere. Therefore there are this amount in every 100 parts of air. So you can multiply both by 10 000 to make it easier to work with making 0.09 ppm of xenon!
Empirical and molecular formulas? Are ratios empirical- smallest whole number ratio of atoms in a compound. Molecula- gives the actual number of atoms in a molecule. (for more info see page 8 & 9 in textbook)
Look at page 10 & 11 for equations and calculations and page's 12 & 13
Created by: brontemunro