What is an element?
An element is a substance that cannot be split into simpler substances by chemical means.
What contribution did Dobereiner make to the periodic table? (3 points)
Triads, Li-Na-K or Cl-Br-I, mass of the middle is an average of the first and third.
What contribution did Newland make to the periodic table? (3 points)
Octaves, every 8th element had similar properties, only worked for the first 16, tried to make them fit into a table, didn’t take into account undiscovered elements, arranged by increasing atomic mass.
What contribution did Mendeleev make to the periodic table? (3 points)
Arranged elements by increasing mass, left gaps for undiscovered elements, switched Te and I to make them fit in a column with similar properties, didn’t know about noble gases.
What is the difference between Moseley’s periodic table and Mendeleev's periodic table?
Mendeleev’s Periodic Table | Modern Periodic Table |
Elements listed in order of increasing atomic mass | Elements listed in order of increasing atomic number |
Noble gasses missing (undiscovered) | Noble gasses now included |
No atomic numbers listed (undiscovered) | Atomic numbers now listed, discovered by Moseley |
d-Block elements arranged as subgroups | d-Block elements now listed in a separate block |
Gaps left for undiscovered elements | All gaps filled |
What is the mass number?
The mass number of an element is the sum of the number of protons and neutrons in the nucleus of an atom of that element.
What is the definition for relative atomic mass?
The relative atomic mass is defined as the average of the mass numbers of the isotopes of the element, as they occur naturally, taking their abundance into account and expressed on a scale in which the atoms of the carbon-12 isotopes have a mass of exactly 12 units.
What are isotopes?
Atoms of the same element with different mass numbers due to the different amounts of neutrons.
What are the 5 parts of the mass spectrometer in order?
Vaporisation, ionisation, acceleration, separation, detection.
Why are Cr and Cu exceptions when writing the s, p, configurations?
Cr - better having a half filled 3d - more stable 4s1, 3d5
Cu - better having a full 3d - more stable. 4s1, 3d10
How many electrons can the 3rd energy level hold?
18
How many electrons in an S orbital, P orbital and D orbital?
S = 2, p = 6, d = 10
Why does the 4s orbital come before the 3d orbital?
Takes less energy to go into the 4s than the 3d
What is the difference between the 3p orbital and a 3p sublevel?
The 3p sublevel is a level within the 3rd energy level (n = 3)
The 3p orbital is a dumbbell shape, and is split into px, py and pz.
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