Classifying the Elements: The Periodic Law and the Periodic Table
- When the elements are arranged in order of increasing atomic mass, certain sets of properties recur periodically.
- The law is based on atomic volume, or atomic mass divided by the density of its solid form.
- The atomic volume increases as you go down in each growth, with the first group having the largest atomic volume.
- In group one, the melting point also decreases as you go further down, but that is limited to the first group only.
Metals and Nonmetals and their Ions
- Metalloids are elements that look like metals, but they have some nonmetallic properties
Ionization energy is the amount of energy a gaseous atom must absorb to be able to expel an electron.
Mg(g) -> Mg+(g) + e-
Mg+(g) -> Mg2+(g) + e- I2 = 1451 kJ/mol
The reason there is an I 1 and and I 2 is that they are the ionization energies to release another electron to get it to that number. So, the first I is called the first ionization energy, and the second is called the second ionization energy, and so on.
RULE: Ionization energies decrease as atomic radii increase.
Ionization is the energy an atom must absorb to expel an atom. Electron affinity is the measure of the energy change that occurs when a gaseous atom gains an electron.
When an atom gains an electron, it gives off energy, making it an exothermic reaction.