Chapter 4 - The Periodic Table Flashcards
Greek philosophers believed there were four elements, what were they?
Earth
Air
Fire
Water
What was Robert Boyle’s definition on an element?
A substance that cannot be split into a simpler substance by chemical means
What did Humphry Davy do?
○Split water into hydrogen and oxygen using electricity
○Tried this with other compounds
○Discovered potassium in this way in 1807 as globules caught fire during the experiment
○Later extracted calcium from lime
○Also discovered Ba, St and Mg
Who arranged elements into triads?
Dobereiner
Triad
A group of three elements with similar chemical properties in which the atomic weight (relative atomic mass) of the middle element is approximately equal to the average of the other two
Give three examples of Dobereiner Triads
Chlorine, Bromine and Iodine
Calcium, Strontium and Barium
Lithium, Sodium and Potassium
Newland’s Octaves
Arrangements of elements in order of increasing atomic weight in which the first and eighth element, counting from a particular element, have similar properties
What were the problems with Newland’s Octaves?
►Some groups didn’t match up
►Noble Gases hadn’t been discovered yet, so it should have been every ninth element
►Should have left gaps for undiscovered elements
►Only works for the first 16 elements
►Got a lot of criticism
Mendeleev’s Periodic Law
When elements are arranged in order of increasing atomic weight (relative atomic mass), the properties of the elements recur periodically
What did Henry Mosely do?
Used x-rays to count protons and discovered that each element had a different and unique number of protons in its nucleus and this is what caused each element to have unique properties
Atomic number
Number of protons in the nucleus of that atom
Modern Periodic Table
Arrangement of electrons in order of increasing atomic number
Modern Periodic Law
When elements are arranged in order of increasing atomic number, the properties of the elements recur periodically, i.e. the properties displayed by an element are repeated at regular intervals in other elements
Nucleus (atom)
Dense centre of an atom where protons and neutrons are found
Mass number
Sum of the number of protons and neutrons in the nucleus of an atom of that element
Isotopes
Atoms of the same element (i.e. they have the same atomic number) that have different mass numbers due to the different number of neutrons in the nucleus
What did Francis William Aston do?
Used a mass spectrometer to measure the number of atoms and discovered samples of an element that had atoms of different masses. He also calculated their % abundance in the sample
Relative atomic mass
The average of the mass numbers of the isotopes of that element
○as they occur naturally,
○taking their abundances into account and
○expressed on a scale in which the atoms of the carbon-12 isotope have a mass of exactly 12 units
What are the stages in a mass sectrometer?
- Vapourisation
- Ionisation
- Acceleration
- Deflection
- Detection
Principal of Mass Spectrometry
Charged particles moving in a magnetic field are deflected to different extents according to their masses and are thus separated according to their masses
What are the uses of a mass spectrometer?
○Identify the presence of isotopes
○Measure the relative abundance of isotopes
○Measure Ar and Mr
○identify unknown compounds like drugs
Electron configuration
Shows the arrangement of electrons in an atom of an element
How many electrons can the s sublevel hold?
2
How many electrons can the p sublevel hold?
6 (two in each p orbital)
How many electrons can the d sublevel hold?
10 (two in each d orbital)
Aufbau Principal
When building up the electronic configurations of atom in the ground state, electrons occupy the lowest available energy level
What order do you fill up orbitals?
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, ….
What elements break the pattern in the first row of d-block?
Cr
Cu
Ions
Are atoms (r groups of atoms) which carry an electric charge because they have either gained or lost one or more electrons
How do you write the electronic structure of s- and p-block ions?
Write the electronic structure for the neutral atom and then add (for negative ion) or subtract (for positive ion) electrons
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
Paulis Exclusion Principal
No more than two electrons may occupy an orbital and they must have opposite spin
Clarify the difference between energy levels, energy sublevels,and individual orbitals
energy levels → n=1, n=2…
energy sublevels → 1s, 2s, 2p…
individual orbitals→ 2px, 2py, 2pz
