What is the maximum number of electrons that can fill the first four shells?
2n^2 = 32 (n = shell number)
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What are shells?
Energy levels.
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Define atomic orbital.
A region around the nucleus that can hold up to two electrons with opposite spins. There are different types of orbitals: s-, p-, d- and f-orbitals.
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How many orbitals are there per shell?
from n= 1 there's 1 s-orbital in each shell, from n= 2 there's 3 p-orbitals in each shell, from n = 3 there's five d-orbitals in each shell.
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What are the shapes of s- and p- orbitals?
s- orbital = sphere. p-orbital = dumb-bell shape
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How do orbitals fill?
In order of increasing energy: 1s^2, 2s^2, 2p^6, 3s^2, 3p^6, 3d^10
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How do orbitals with the same energy fill?
Before the electrons pair up, each orbital is occupied singly. This prevents any repulsion between paired electrons until there is no further orbitals available at the same energy level.
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Define ionic bonding.
The electrostatic attraction between positive and negative ions.
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What is the structure of ionic compounds like?
Each ions attracts oppositely charged ions in all directions, resulting in a giant ionic lattice.
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What are the properties of ionic compounds?
High melting and boiling points, dissolve in polar compounds, Conduct electricity in liquid/aqueous state only.
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Why don't ionic compounds conduct electricity when solid?
In solid state the ions are in fixed positions in the lattice and there are no mobile charge carriers (no free electrons)
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Define covalent bonding.
strong electrostatic attraction between shared pain of electrons.
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Define a dative covalent bond.
A covalent bond where the shared pair of electrons has been supplied by one of the bonding atoms only.
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What is the average bond enthalpy?
A value used to measure how strong the covalent bond is.
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Describe the Electron-pair repulsion theory.
The electron pairs repel one another so that they are arranged as far apart as possible. Lone pair - lone pair angles are the biggest, bonded pair-bonded pair angles are the smallest.
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Name the shape of a molecule with 4 bonded pairs and no lone pairs. Give bond angle.
Tetrahedral. 109.5*
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Name the shape of a molecule with 3 bonded pairs and 1 lone pair. Give bond angle.
Pyramidal. 107*
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Name the shape of a molecule with 2 bonded pairs and 2 lone pairs. Give bond angle.
Non-linear. 104.5*
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Name the shape of a molecule with 4 bonded pairs in 2 bonding regions. Give bond angle.
Linear. 180*
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Name the shape of a molecule with 3 bonded pairs in 3 bonding regions. Give bond angle.
Trigonal planar. 120*
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Name the shape of a molecule with 6 bonded pairs in 6 bonding regions. Give bond angle.
Octahedral. 90*
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Define electronegativity.
The ability of an atom to attract the bonding electrons in a covalent bond. Increases towards F in the periodic table.
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Define intermolecular forces.
Weak interactions between dipoles of different molecules. Largely responsible for physical properties such as melting and boiling points.
Movements of electrons produces a dipole in a molecule. This is an instantaneous dipole. It can cause an induced dipole on a molecule next to it, causing a chain reaction and causing all molecules to attract each other. It is temporary and weak.
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Describe permanent dipole-dipole interactions.
Occur in polar molecules as those have permanent dipoles. Similar to London forces but results in stronger forces.
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Define simple molecular substances
Made up of small unis containing a definite number of atoms with a definite molecular formula.
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Describe simple molecular lattice.
The molecules are held in place by weak intermolecular forces, and the atoms within each molecule are bonded together strongly by covalent bonds.
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What are the properties of simple molecular substances?
Low melting and boiling points, soluble if polar only, do not conduct electricity as there are no mobile charged particles.
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Define Hydrogen bonding.
A special type of permanent dipole-dipole interaction found between an electronegative atom with a lone pair of electrons and a hydrogen atom attached to an electronegative atom.
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What are the properties of water?
Solid ice is less dense than water as hydrogen bonds hold water more further apart in the lattice when solid, water has a high melting and boiling point, it has a high surface tension and viscosity.
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