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Atomic structure by Mind Map: Atomic structure
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Atomic structure

periodic table

atomic number

number of protons

mass number

number of protons and neutrons

What makes up an atom?

electron arrangement

2,8,8,8

nucleus

Protons (P+)

Neutrons (n)

ionic bonding

Metal + non-metal transfer electrons to from anions (-) and cations (+)

Ionic bonds are held together by strong electrostatic attractions between ions

Ions from a solid crystal lattice of alternating cation and anion

covalent bonding

Form between two or more non-metal atoms

Electrons are shared between atoms

Lewis structures

Total all valence electrons in the molecule

Place a pair of electrons into a bonding position between each atom

Place remaining pairs around the outer atoms so that they each have 8 electrons

If there are any remaining electron pairs place them around the central atom

Check the central atom has 8 electrons. If not move a non-bonding pair into a bonding position until the central atom has 8 electrons

Shapes of molecules

Tetrahedral, 4 groups off the central atom, Bond angle 109.5o

Trigonal pyramid, 3 groups off the central atom, Bond angle 109.5o, one pair of non-bonding electrons on the central atom

Trigonal planar, 3 groups off the central atom, Bond angle 120o, no non-bonding electrons off the central atom

bent, 2 groups off the central atom, 4 regions of electron density around central atom in the form of 2 pairs of non-bonding electrons, bond angle 109.5o, 3 regions of electron density around the central atom in the form of 1 pair of non-bonding electrons, bond angle 120o

linear, 2 or 1 group off the central atom, Bond angle 180o, no non-bonding pairs of electrons around the central atom.

Bond polarity

Caused by differences in electronegativity, If difference in electronegativity is less than 0.5, then the covalent is non-polar, Covalent bond needs to contain F,O, N to be classified as polar, If difference in electrnegativity is greater than 4.0, then the bond will be ionic and electrons will not be shared.

Polar covalent molecules

occur when the bond polarities do not cancel., when polar bonds are in the same plane, the the polarities will cancel eg in SO3. This is non-polar

Properties of ionic compounds

solubility

variable solubility in water (see solubility rules)

electrical conductivity

as molten and solution only as need free moving ions

melting point

high, due to strong electrostatic attraction between ions

hardness

brittle, when forced, layers of ions shift causing positive and negative ions to align and repel.

Metallic bonding

made up of metal atoms stacked in a lattice and a sea of free valence electrons

electrostatic attraction between atoms and valence electrons is non dimensional and strong

Properties of covalent compounds

giant covalent networks

diamond structure, solubility, insoluble in water and non polar substances, electrical conductivity, nil, no free electrons, melting point, very high -strong covalent bonds, hardness, very hard- strong covalent bonds

silicon dioxide structure

bucky balls structure

graphite structure, solubility, insoluble in water and nonpolar solvents, electrical conductivity, conducts electricity due to free electrons between layers, melting point, very high- strong covalent bonds, hardness, layers slide over eachother - weak Van Der Waals forces between layers

simple covalent molecules

solubility, soluble in water if polar, soluble in non-polar solvents if non-polar

electrical conductivity, nil- no free electrons or charged particles

melting point, Very low - MP is dependant on size of atoms in the molecule

hardness, nil, mostly gas, liquids of soft solids at room temperature

Breaking Van Der Waals forces

dipole-dipole interactions, in molecules containing polar covalent bonds

Hydrogen bonding, between molecules containing O, H or F atoms, these are stronger than the other types of Van Der Waal forces, This leads to higher than expected melting points

instantaneous dipole moments, halogens, melting point increases down the group, halogens contain non-polar covalent bonds have instantaneous dipole moments occurring between molecules., in molecules containing non-polar covalent bonds, These dipole moments get stronger the more electrons there are in the molecule