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Ionization energy is the energy required to remove one electron from an atom. The stronger the electrostatic attraction the harder it is to remove.
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Electronegativity is the tendency of an atom in a bond to draw the bonding electron towards itself.
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Ionization energy increases along periods and up groups.
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Electronegativity follows the trend of ionization energy.
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Simple equation?
Balance normally
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Combustion reaction? (CHO)
Carbon, then hydrogen, then oxygen.
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Complex equation?
Simultaneous equations in which each substance has a variable, and an equation is written for each element.
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Melting point
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Related to strong electrostatic attraction
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Malleability
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Whether the substance can be shaped or snaps. Depends on how the attraction changes when it is deformed or stressed.
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Electrical conductivity
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Needs mobile charged particles.
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Combination
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Two or more reactants come together to form a product
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Decomposition
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A single reactant breaks into two or more products
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Single displacement
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A singular element displaces another element in a bond
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Double displacement
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Two substances break down and the cations and anions switch
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Combustion
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Reaction of oxygen with a fuel. When complete it produces carbon dioxide and water.
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Ionic bonding occurs between a metal and a non metal ion with the electrostatic attraction between the ions. The electron will leave the low electronegative metal and move to the high electronegative non-metal.
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Properties of ionic substances:
- High melting point (strong bonds) - Brittle (when deformed ions repel) - Non-conductive when solid - Conductive when dissolved in water (aqueous) |
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Covalent bonding occurs between two non-metals that have high electronegativity. This means that neither atom wants to give up electrons and they rather share them.
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The electrostatic attraction occurs between the positively charged nucleus and the negatively charged electrons. The positive nuclei will repel each other.
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The electrons move around the two atoms freely however they spend most of the time in between. Unlike metallic bonds the electrons are unable to drift away.
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In general the shorter the bond the stronger the electrostatic attraction. This is because the distance that balances the attractive and repulsive forces balance is shorter.
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Properties:
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Molecular covalent
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Covalent lattice
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-Low melting point
-Brittle as solid, weak -Doesn't conduct |
-High melting point
-Brittle but strong -Doesn't conduct |
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Shows the atoms involved in bonding.Only the valence electrons are shown.
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A single bond has two electrons and can be represented as two dots or one line.
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The fewer the valence electrons the more bonds the atom can form.
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If the atom is smaller it usually forms stronger bonds, however if there are multiple bonding pairs it will be stronger.
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Atoms don't always bond the same way. An allotrope is a different bonding arrangement of a certain element.
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Different bonding at the atomic level leads to different properties on the macroscopic level.
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Example 1: Carbon
Diamond: three-dimensional tetrahedral lattice hard, strong, clear, nonconductive. Graphite: two-dimensional hexagonal lattice soft, grey, conductive. Amorphous carbon (coal, soot): no regular pattern, but three-dimensional bonding. soft, black, nonconductive |
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Example 2: Tin
alpha-tin: covalent lattice structure like diamond grey, dull, crumbly beta-tin (stable above 13°C): metallic lattice Silvery-white, malleable. |
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Metallic bonding occurs between two metals. Due to the low ionization energy metals lose their electron easily. The repulsion from the neighbouring ions repel while the electrons act as a glue pulling it together.
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Properties:
- Melting points vary (reflects range of bond strength) - Malleable (Electrons act as glue, whatever the shape) - Conductive (The electrons move freely) |
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Scientific notation
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Count place values from new and old decimal point
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Decimal notation
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Count place values specified by the exponent
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Significant figures
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-Non zeros count
-Captive zeros count -Leading zeros don't count -Trailing zeros after decimal count |
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Multiplying and dividing
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Give your answer to the smallest number of sig figs given
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Adding and subtracting
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Give your answer to the number of decimal places used
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The empirical formula is the lowest whole-number ratio of atoms in a substance. For a lattice the empirical formula will be the same.
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For molecular substances they will be expressed in a molecular formula which can sometimes be simplified.
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The empirical formula can be derived from mass percentages using the pneumonic:
Percent to mass, Mass to moles, Divide by small Times ‘til whole. |
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We can find the molecular formula by finding the simplification factor which is the molecular molar mass divided by the empirical molar mass.
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Cheatography n. The art of mapping complex subjects into clear, instantly navigable reference guides.
