Module 2: Foundation in Chemistry
- Created by: Mollymadworld
- Created on: 11-06-18 20:29
2.1.1 Atoms and Reactions
A particle consists of; protons, neutrons, electron.
Protons - Same mass as a neutron so is regarded as 1
- Have a +1 Charge
- Is within the nucleus
- Different elements have different numbers of protons
- The number of protons is the atomic number
Neutrons - Same mass as a proton so is regarded as 1
- Have a neutal charge
- Is within the nucleus
- Mass number - atomic number = neutrons
Electrons - Mass is 1/1836
- Have a -1 Charge
- Electrons cancel out the positive charge from the protons
- Electrons are held within sheilding
Istopes; Same number of protons just different number of neutrons resulting in a different mass. Isotopes of the same element contain the same electron structure so react in the same way, however there may some small physical changes e.g. higher melting point, boiling point, density.
Ions; An ion is a charged atom. The number of electrons is different from the number of protons.
- Cations are positively charged and have fewer electrons than protons.
- Anions are negatively charged and have more electrons than protons.
Relative Isotopic Mass - Is the mass of an isotopic relative to 1/12th of the mass of an atom of carbon-12.
Relative Atomic Mass - Is the weighted mean mass of an atom of an element relative to 1/12th the mass of an atom of carbon-12.
The weighted mean mass takes into account;
- Percentage abundance of each isotope.The relative isotopic mass of each isotope.
- The percentage abundances of the isotopes in a sample of an element are found experimentally using a mass spectrometer.
- This method is limited to ions with single charges.
Relative atomic mass = (Abundance x Atomic number) / Total abundance
For simple molecules the term relative molecular mass will be used.
For compounds with giant structures, the term relative formula mass will be used.
2.1.2 Compounds, formulae and equations
Simple ions from the periodic table;
- Group one - 1+
- Group two - 2+
- Group three - 3+
- Group five - 3-
- Group six - 2-
- Group seven - 1-
Other noteworthy ions = Ag+, Zn 2+
Some metals, usually transitional metals can form ions with different charges.
- Copper can form two ions - Copper (l), Cu +. Copper (ll), Cu 2+.
- Iron can form two ions - Iron(ll), Fe 2+. Iron (lll), Fe 3+.
Polyatomic ions; NH4 +, OH-, NO3 -, NO2 -, HCO3 -, MnO4 -, CO32-, SO42-, SO22-, Cr2O72-…
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