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Atomic Structure
Structure of the Atom
Relative atomic mass (Ar)
The weighted average mass of an atom of an element, taking into account its naturally occurring
isotopes, relative to one twelfth of an atom of carbon 12
Relative molecular mass (Mr)
The mass of a molecule compared to one twelfth of an atom of carbon 12
Atoms of an element which have identical proton numbers but have a different number of electrons
Isotopes don't affect the chemistry of an element, because all that's different…read more

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The mass spectrometer is used to obtain the mass and percentage abundance of the isotope of an
1. The sample is ionised by bombarding it with high-energy electrons fired from an electron gun
2. The ions are accelerated by attracting them towards a negatively charged plate, which has a
small gap through which they can pass
3. The beam of positively-charged ions are deflected by a magnetic field from an electromagnet,
which can be adjusted
4.…read more

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Trends in ionisation energy
Elements Explanation
H He 1st ionisation energy increases because the atomic radius of He is
smaller than H so the force of attraction between the nucleus and the
electrons is greater
He Ne 1st ionisation energy decreases because Ne is losing an electron from
its 2nd shell, which is shielded by the 1st shell
it is similar from Ne Ar and Ar Kr
He Li 1st ionisation energy decreases because you are removing an electron
from the next shell, which is…read more

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The number of atoms or molecules in one mole is a constant known as Avogadro's Constant; 6.022 x
Molar mass
The mass of one mole of a substance is called the molar mass. The units of molar mass are gmol-1
mol = mass/Mr
Amount of substance per unit of volume
Concentration (moldm-3) = moles/volume (dm3)
Moles & gases
PV = nRT
P = Pa, T = K, R = 8.…read more

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Molecular formula
The actual number of atoms of each element in one molecule
Calculating molecular formula
1. Calculate the % of each element (mass/total mass)
2. Divide each % by the Ar of each element
3. Divide each answer by the smallest answer
4. Determine the empirical formula
5. Compare the Mr of each compound to mass of empirical formula
6.…read more

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Metallic bonding
Metals are shiny elements made up of atoms which can easily lose up to 3 outer electrons, leaving
positive ions
In a metal element, the outer shells merge; the outer electrons are no longer associated with a particular
Metals consist of a lattice of positive ions, surrounded by a `sea' of delocalised outer electrons
The positive ions in the lattice tend to repel each other, and this is balanced by the electrostatic
attraction of these positive ions for the negative `sea'…read more

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Pure carbon with covalent bonding throughout
Giant structure; bonding spread throughout the structure
Each carbon atom forms 4 single covalent bonds with other carbon atoms
The bonds point to the corners of a tetrahedron, as the bonds repel as far apart as possible
Atoms form a giant 3D lattice of strong covalent bonds
Very hard
Very high melting point
Does not conduct electricity ­ there are no free charged particles to carry charge
Pure carbon with two sorts of bonding; strong covalent &…read more

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Ionic bonding
Bonds between two oppositely-charged ions
Between groups 1&2 and groups 6&7
Electrostatic force of attraction
Metals have low ionisation energies; can lose electrons easily to form positive ions
Non-metals have high electron affinities; gain electrons easily to form negative ions
Oppositely charged ions are attracted electrostatically and form giant ionic crystals
Properties of ionic compounds
Very strong ­ giant structure with strong ionic bonds
High melting point ­ giant structure with strong ionic bonds
Conduct electricity when molten or in solution ­ ions…read more

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The ability of an atom to attract the bonding electrons towards itself in a covalent bond
If either atom has electronegativity greater than 1.9 & the difference in electronegativity between the
two atoms is similar (less than 0.5), the bonding is covalent
If the difference is large (greater than 2.1), the bonding is ionic
If either atom has electronegativity greater than 1.9 and the difference is between 0.5 and 2.…read more


umar ali

are these the only notes you used and how did you do on the exam


These are brill, I'm resitting for an A and really couldn't find the energy to sieve through the **** in the textbook. Thank-you! 

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