UNITS 3&13- PERIODICITY

Essential ideas:

The arrangement of elements in the periodic table helps to predict their electron configuration.
Elements show trends in their physical and chemical properties across periods and down groups.
The transition elements have characteristic properties; these properties are related to their all having incomplete dsublevels.
d-orbitals have the same energy in an isolated atom, but split into two sub-levels in a complex ion. The electric field of ligandsmay cause the d-orbitals in complex ions to split so that the energy of an electron transition between them corresponds to aphoton of visible light.

What’s the periodic table?

The periodic table is a super awesome highly organised big chart that contains loads of relevant information about the elements.

The main block elements (also called the main group elements) in which the outermost electrons are s- and p- electrons.
F block metals metals are the guys at the bottom, where the outermost electrons are in f-orbitals.
D block metals are the green ones on the chart, with their outermost electrons in d-orbitals.

Groups:

The groups on the periodic table consist of the elements in each column of the periodic table. Elements in the same group of the periodic table have chemical properties due to the fact that they have the same number of valence electrons, and similar electron configurations.

Group 1 – Alkali metals. With the exception of hydrogen, the elements in group 1 are the alkali metals. These elements are metallic , soft, have low melting points, and are very reactive. This reactivity is caused by a burning desire to lose one valence electron to become like the most recent noble gas.
Group 2 – Alkaline earth metals. The alkaline earth metals are less extreme versions of the alkali metals. Reactive, but nowhere near as reactive as the alkali metals with low density (but higher than the alkali metals) and are fairly soft (but harder than alkali metals).
Groups 3-12 – Transition metals. When you think of your stereotypical metal, you’re thinking of a transition metal. Transition metals are generally hard, have high melting and boiling points, and have high density.
The first row of elements at the bottom – Lanthanides. Sometimes called the “rare-earth” or “lanthanoids”, these elements have properties similar to those of the alkaline earth metals. They’re used in small quantities in various scientific and industrial applications.
The second row of elements at the bottom – Actinides. The actinides have properties similar to the alkaline earth metals, except that they’re very dense with very high melting points. All of the actinides are radioactive, and many are not found in nature and need to be artificially synthesized.
Group 18 – Noble gases. The main property of the noble gases is that they’re stable. Like, really, really stable. You can do all sorts of stuff to noble gases and not much will happen with them. The reason they’re so stable is that they want to have a full electron shell, and since they already have that, they actually resist reactions. Some people have made a few noble gas compounds, but they don’t stick around long.⁹
Group 17: The halogens. The halogens are super reactive because they really really want to gain one more electron to get a full valence shell. They are only one element short of having a stable octet so readily react to make that happen. Halogens are diatomic elements (they have the general formula X2) and are used for loads of applications.
Hydrogen: The weirdo. Doesn’t really share the properties of the alkali metals. For one thing, it’s a diatomic gas not a metal. For another, it tends to either lose electrons (like the alkali metals) or gain electrons (like the halogens), but is far less reactive than either.

Metals, nonmetals, and metalloids

Metals:

In metals, delocalised electrons hold the atoms together. All of the electrons do all of the bonding in the entire chunk of metal and kind of float around holding everything together at once.

Metals conduct electricity because the electrons can move from one side of the metal to the other. Metals are bendy because the atoms aren’t locked tightly in place and can shift without destroying the network of bonds.

Nonmetals: Nonmetals that are solid are brittle, hard, and don’t conduct electricity because they have rigid localized bonds.

Metalloids: Metalloids have bonding that’s somewhere between metals and nonmetals. In metalloids, the bonds in metalloids become more delocalized when their temperature is increased or when high voltage electricity is applied.

Because the bonding in metalloids are similar to those with metals and nonmetals, the properties also tend to be somewhere in the middle. This includes the following: