Periodic table - Ch4 Flashcards
Boyle
Element: substance that cannot be split into simpler substances by chemical means
Davy
Passed electricity through salts and discovered lots of elements. (Eg. K)
Dobereiner triads
Groups of three elements, with similar chemical properties, in which the atomic weight of the middle element is the average of the other 2 elements. (Eg. Li, Na, K)
Newlands (law of octaves)
Elements in order of increasing atomic weight with the 8th under 1st according to similar chemical properties.
Mandeleev
Elements in order of increasing atomic weight. Left gaps + switched Te and I to be in the same group as similar chemical properties.
Moseley
Discovered atomic numbers using x-rays. (Proved mandeleev theory of switching Te and I)
Diff. today’s and mendeleevs P.T
Todays:
- More elements
- No gaps
- Increasing atomic number
Mendeleevs:
- Less elements
- Gaps
- Increasing atomic weight
Isotope
Atoms of same element with same atomic number but different mass number.
Principles of mass spectrometry
- Vaporisation
- Ionisation
- Acceleration
- Separation in a magnetic field according to their masses
- Detection
(Uses: drug tests on hair + forensic)
Sub level
Subdivision of main energy level that consists of one or more orbitals of the same energy.
S = 2
P = 6
D = 10
Aufbau principle
Electrons occupy the lowest available energy level called ground state.
Why does 4s fill before 3d?
Requires less energy
Why does lithium want to give out one electron? (Any question like this)
Satisfy octet rule
Hund’s rule of maximum multiplicity
When two or more orbitals of equal energy are available, the electrons occupy them singly before filling them in pairs.
Pauli Exclusion Principle:
No more than two electrons may occupy an orbital and they must have opposite spin.
Electron configuration exception:
Cr and Cu. To be more stable.
Relative atomic mass
Average mass of the isotopes of the element as they occur naturally, c ompared to 1/2 mass of carbon-12 atom.
