Module 2 – Foundations in chemistry

Shapes of Molecules and Ions

Electron- Pair Repulsion Theory: Electron pairs arranged as far apart as possible to minimise repulsion. Number of bond pairs and lone pairs of electrons surrounding central atom determine shape. This holds the bonded atoms in a definite shape. - Name shape. - State...

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Electronegativity and Polarity

Electronegativity: The ability of an atom to attract electrons in a covalent bond. • Periodic Table: - Across the periodic table, the nuclear charge increases and the atomic radius decreases. - Electronegativity increase up the periodic table and across the periodic...

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Hydrogen Bonding

The third of the three intermolecular forces… • Hydrogen Bonding: A strong dipole- dipole attraction between an electron deficient hydrogen atom of –NH, -OH or –HF on one molecule and a lone pair of electrons on a highly electronegative N, O or F on a different...

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Gas- moles

Gas Volumes: At the same temperature and pressure, equal volumes of different gases contain same number of molecules. • Molar Gas Volume: Vm. It is the volume per mole of gas molecules. Volume of gas depends on pressure and temperature. • RTP: At RTP, 1 mole of gas...

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Reacting Quantities

Stoichiometry: The ratio of moles of each substance in a chemical reaction. • Balanced Equation: The balancing numbers gives molar ratio. • Find Moles- Various States: Can have solid go to gas or liquid. If asks to calculate volume of gas, remember there might be more...

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Atomic Structure and Isotopes

Relative: Subatomic particles have tiny masses so use relative masses instead of grams. • Electron: An electron has about 1/ 1800th mass of a proton, positioned in the shell. • Protons: Number of protons identifies element- atomic number, the number on top in periodic...

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Relative Masses

Relative Mass: No units as it is ratio of two masses- it’s relative. • Carbon-12 Isotope: One atom of carbon 12 is 12 atomic mass units. 1 atomic mass unit is 1/12th of an atom of carbon- 12 = mass of a proton or neutron. • Relative Isotopic Mass: It is the mass of an...

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Formulae and Equations

Ion Charges: Group 1 = 1+ ions etc. Group 7 = 1-. • Need to know also Zn2+ and Ag+ . • Transition Metals: Form several ions with different charges. Ionic charge shown with Roman numeral in name. • Binary Compound: Compounds containing two elements. For the second...

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Electron Structure

Shells are energy levels. • Atomic Orbitals: It is region around a nucleus that can hold up to two electrons, with opposite spin. Must have opposite spin due to repulsion between two negative electrons. • Four Different Atomic Orbitals: s-, p-, d- and f-. The greater...

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Ionic Bonding and Structure

Bonding Questions: E.g. melting point question ‘in terms of bonding and structure.’ - Name structure. - Name bond. - Write what the attraction is between e.g. + metal ions and –ve delocalised electrons in metallic, atoms in covalent bond and molecules in simple...

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Covalent Bonding

Covalent Bonding: It is the strong electrostatic force of attraction between a shared pair of electrons and the nuclei of the bonded atoms. Covalent bonding occurs between non- metallic elements and polyatomic ions. • Orbital Overlap: A covalent bond is the overlap of...

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Acids, Bases and Neutralisation

Acids: Solid H2SO4 not an acid, when aqueous it is an acid. They ionise into (2)H + and SO4 2 . Need to know acids- HCl, H2SO4, H3PO4, HNO3 and CH3COOH. • Strong Acid: When dissolved in water, a strong acid completely dissociates in aqueous solution, releasing H + . •...

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Acid- Base Titrations

Titrations: Technique used to accurately measure the volume of one solution that reacts exactly with another solution. Used to find concentration of solution, identify unknown chemicals and find purity of substances. • Volumetric Flask: They make up standard solutions...

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Redox

Oxidation Number: Aka oxidation state. Oxidation number sign placed before the number, unlike ionic. • Rules in Most Cases: - Elements- Oxidation number is zero. Even Cl2. - Most Metals- Oxidation number of group 1, 2 and 3 same as ionic charge, +1 or +2 or +3. Look...

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Moles

Avogadro Constant: One mole = 6.02 x1023 particles, easier way to count number of particles. As mole linked to carbon- 12. 1 mole in grams = relative atomic mass. • Number of atoms = 6.02 x1023 x molar mass. 0.12 moles of S8 molecules means need to multiply by 8 as...

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Determination of Formula

Molecular Formula: Covalent compounds and elements exist as molecules. • Empirical Formula: It is the simplest whole number ratio of atoms of each element in a compound. Used for giant structures of metals and ionic. • Relative Molecular Mass: Mr. Add relative atomic...

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Hydrated Salts

Water of Crystallisation: Water molecules that are bounded into crystalline structure of a compound. • Dot or .xH2O shows number of waters of crystallisation. Anhydrous means no waters of crystallisation. • Copper (II) Sulphate: When blue crystals of hydrated copper...

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Liquid- moles

1 cm3 = 1 ml. 1dm3 = 1000 cm3 . • Concentration: Unit mol dm-3 . It is the amount of solute, in moles, dissolved in each 1 dm3 of solution. • Calculating Moles with Volumes: Moles (mol) = Concentration (mol dm-3 ) x Volume (dm3 ). If in cm3 / 1000 = dm3 . Standard...

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The shapes of simple molecules and ions

The shapes of simple molecules and ions Predict the shape and bond angle of ____. _____ because it has n of electron pairs and n lone pairs. Electron pairs repel to become as far apart as possible. Lone pairs of electrons repel more strongly than bonding pairs. Draw...

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Shapes of molecules and intermolecular forces

Shapes of molecules and intermolecular forces Define ionic bonding An ionic bond is the electrostatic force of attraction between positive and negative ions Explain the solid structures of giant ionic lattices This is a result of oppositely charged ions strongly...

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Acids and redox

Acids and redox Explain the difference between acids, bases and alkalis. Acids dissolve in water and release H+ ions in aqueous solution. They are proton donators.  A base neutralises an acid to form a salt. Alkalis are water-soluble bases that dissolve in water to...

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Acid-Base Titrations

Describe the techniques and procedures used when preparing a standard solution of required concentration and carrying out acid–base titrations. A standard solution is a solution with a known concentration. Weigh the solid substance and divide this number by its...

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Electrons and bonding

Electrons and bonding Describe the number of electrons that can fill the first four shells. 1st shell = 2                          2nd shell = 8                         3rd shell = 18                       4th shell = 32 Define atomic regions / orbitals. A region...

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Amount of Substance

Amount of Substance Define relative isotopic mass. The mass of an isotope relative to 1/12 of the mass of an atom of carbon-12. Define relative atomic mass. The relative atomic mass is the weighted mean mass of an atom of an element relative to 1/12 of the mass of an...

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