Atomic Structure

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The atomic number of an atom is:
the number of protons in the nucleus of one atom of the element.
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The mass number of an atom is:
the number of protons + the number of neutrons in the nucleus of one atom of the element.
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Isotopes are:
atoms of the same element with the same number of protons and electrons but different number of neutrons. Therefore they have the same atomic number but different mass number.
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Why are the chemical properties of isotopes of the same element almost identical?
Because isotopes have the same number of protons and electrons, and chemical reactivity is influenced by the number of protons and electrons.
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The different physical properties isotopes show are:
1) Rate of diffusion which depends on mass. 2) Slightly different boiling points (the heavier it is, the more energy needed to break it apart). 3) Nuclear properties such as radioactivity.
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Relative Atomic Mass is:
the average mass of one atom of an element multiplied by twelve, divided by the mass of one atom of 12C.
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The calculation for RAM is:
(mass x abundance of atom 1) + (mass x abundance of atom 2) + etc.
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What is covalent bonding?
Two atoms share one or more pairs of electrons.
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What is ionic bonding?
One or more electrons are transferred from a metal to a non-metal.
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What is coordinate bonding?
One atom donates a lone pair of electrons to an empty orbital on another.
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What is metallic bonding?
Outer electrons delocalise, resulting in positive ions in a sea of electrons.
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What is electronegativity?
It is an element's ability to attract the bonding electron pair, measured on the Pauling scale, in a covalent bond.
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The H3O+ ion is also known as:
hydroxonium ion, hydronium ion, and oxonium ion.
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The strength of metallic bonding depends on:
1) The charge on the metal ions. 2) The size of the metal ions.
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How does the charge of the metal ion affect the strength of bonding?
The greater the charge on the metal ion, the greater the attraction between the ions and the delocalised electrons, and the stronger the metal ions.
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How does the size of the metal ion affect the strength of bonding?
The smaller the metal ion, the closer the positive nucleus is to the delocalised electrons. This means there is a greater attraction between the two, which creates a stronger metallic bond.
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Why isn't electron density shared equally in a covalent bond between two different elements?
Because different elements have differing electronegativities.
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The electronegativity of an element depends on:
1) Atomic radius. 2) The number of unshielded protons.
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How does atomic radius affect electronegativity?
As the radius of an atom increases, the bonding pair of electrons become further from the nucleus. They are therefore less attracted to the positive charge of the nucleus, resulting in a lower electronegativity.
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How does the number of unshielded protons affect electronegativity?
The greater the number of protons in a nucleus, the greater the attraction to the electrons in the covalent bond, resulting in a higher electronegativity. However, full energy levels shield the electrons in the bond from the increased attraction.
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Electronegativity increases across a period because:
1) Atomic radius decreases. 2) The charge of the nucleus increases without significant extra shielding. New electrons do not contribute much to shielding because they are added to the same outer shell across the period.
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Electronegativity decreases down a group because:
1) The atomic radius increases. 2) Although the charge on the nucleus increases, shielding also increases significantly. This is because electrons added down the group fill new energy levels.
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What does it mean when the electronegativity of both atoms in a covalent bond is identical?
It means the electrons in the bond will be equally attracted to both atoms, resulting in a symmetrical distribution of electron density between the two.
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Why is bonding in elements always non-polar?
The electronegativity of the atoms in each molecule is the same.
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What is the effect of electronegativity on polar bonds?
The greater the electronegativity difference between two atoms in a bond, the greater the polarisation of that bond.
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Why aren't molecules containing polar bonds always polar?
If the polar bonds are arranged symmetrically, the partial charges cancel out and the molecule is non-polar, and vice versa.
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As polarisation increases, the character of the bonding changes from ______ to ______
It changes from covalent to ionic.
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What are intermolecular forces?
These are forces between a molecule and its neighbouring molecule.
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Do all molecules experience intermolecular forces?
Yes, although some are very weak.
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How does molecular size affect the strength of the dispersion forces?
The more electrons you have, and the more distance over which they can move, the bigger the possible temporary dipoles and therefore the bigger the dispersion forces.
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How does molecular shape affect the strength of the dispersion forces?
Long, thin molecules can develop bigger temporary dipoles.
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What is an orbital?
A region where an electron may be found.
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Why can each orbital only hold a maximum of two electrons?
Electrons in the same orbital cannot have the same spin, and since there's only two different spins (anticlockwise and clockwise), there can only be two electrons.
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What is the Pauli Exclusion Principle?
Each orbital can contain a maximum of 2 electrons - 1 spin up and 1 spin down.
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How many orbitals do the following sub-levels contain? 1) s; 2) p; 3) d; and 4) f.
1) one; 2) three; 3) five; and 4) seven.
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What is the Aufban Principle?
Electrons fill energy levels in order of increasing energy.
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What is the Hund's rule?
Electrons will occupy orbitals as single, unpaired electrons all with the same spin. They will only begin to pair up when there are no more empty orbitals in that sub-level.
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When electrons pair up, there are _____ forces between them.
Repulsive.
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What is ionisation energy?
The first ionisation energy is the energy needed to remove 1 electron from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous +1 ions.
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Are ionisation energies endothermic or exothermic?
Endothermic.
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The lower the ionisation energy, the _____ it is to form an ion.
easier
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The factors affecting ionisation energy are:
1) Nuclear charge. 2) Distance from nucleus. 3) Shielding.
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Ionisation energies provide vital information about:
1) Evidence of periods. 2) Evidence of groups. 3) Shell structure.
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What is the second ionisation energy?
The second ionisation energy is the energy needed to remove 1 electron from each ion in one mole of gaseous +1 ions to form 1 mole of gaseous +2 ions.
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What are successive ionisation energies?
This is when you keep removing single electrons from an atom until just the nucleus is left.
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How can we tell the number of electrons in each main energy level of an element using ionisation energies?
Look for the jumps in successive ionisation energies.
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What is the general trend in ionisation energies across a period?
Ionisation energies generally increase across a period because the nuclear charge is increasing and this makes it more difficult to remove an electron.
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Why is the increase in ionisation energies across a period not regular?
If the outer electron of an element is alone in a slightly higher energy level than the outer electron of the last element, it requires less energy to remove it. This is also true for when the outer electrons go from being single to being paired.
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What is the general trend in ionisation energies down a group?
There is a general decrease in first ionisation energies going down the group because the outer electron is in a main level that gets further from the nucleus in each case.
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Card 2

Front

The mass number of an atom is:

Back

the number of protons + the number of neutrons in the nucleus of one atom of the element.

Card 3

Front

Isotopes are:

Back

Preview of the front of card 3

Card 4

Front

Why are the chemical properties of isotopes of the same element almost identical?

Back

Preview of the front of card 4

Card 5

Front

The different physical properties isotopes show are:

Back

Preview of the front of card 5
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