Periodic Table Families

If you arrange the elements in order of atomic number, certain patterns emerge. One of these patterns is that elements in vertical columns behave similarly. These are known as groups or families. Examples are shown in the table below:

Family	Members	Valence Number (see definition below)	Common ion formed when reacting	Physical properties	Chemical properties
Alkali Metals Alkali = Arabic for ashes. Ashes are basic (opposite of acids)or alkaline.	Li, Na, K, Rb, Cs, Fr	1	+1	Soft, low melting, shiny metals: conduct heat and electricity	React vigorously with acids, water, oxygen and halogens. The reaction with water generates hydrogen gas and a base.
Alkaline earth metals	Be, Mg, Ca, Sr, Ba, Ra	2	+2	Harder, higher-melting metals: conduct heat and electricity	React with acids, water, oxygen and halogens, but not always as violently as alkali metals. The reaction with water also generates hydrogen gas and a base, but unlike the alkali metal bases, these are not too soluble in water, just like mud or “earth”, hence their name.
Halogens	F, Cl, Br, I, At	7	-1	Some are gases (Cl₂ and F₂), liquid (Br₂) and solids(I₂, At₂) at room temp. No other family is found in all three states at room temperature. Poor conductors.	React with most metals, and form diatomic molecules. F₂ is so reactive that it will attack gases that would not normally react such as Xe.
Noble or "Inert gases"	He, Ne, Ar, Kr, Xe, Rn	8	0	All gases at room temperature. Poor conductors.	Generally, not chemically active. None of the noble gases are flammable. They will only react with strong electron muggers

Valence Number: number of electrons found in last shell or energy level.(need not be memorized: just count number of horizontal blocks in periodic table from left to right, until you get to that element.)

Why Families Assume A Certain Charge

Why is the common ion for alkali metals +1, but +2 for alkaline earths and -1 for halogens? Each of the above families strives to get a noble gas electron arrangement. Alkali metals all have one valence electron, one more than what the nearest noble gas has. So they like to lose it and form a +1 ion. Remember electrons have a negative charge. So by losing 1 electron, they end up with one more proton (positive charge) than electrons:

Charge = # of protons - # of electrons

Each halogen has 7 valence electrons, 1 less than the neighbouring noble gas. So they like to gain an electron to imitate the stable noble gas shell diagram.

For this reason, noble gases are relatively inert, but halogens, alkali metals and alkaline earth metals are all very reactive. In nature are not found in their neutral state: they have already reacted! Instead we find them in compound form: as ions bounded to other ions.

Examples:

Alkali Metals

Sodium is found in oceans, neurons and in minerals but always in the Na⁺¹ form. Na would destroy living cells and cause explosive reactions in the ocean. To make it, we pass electricity through molten NaCl, thus forcing Na⁺¹ to take back its electron.

Alkaline Earth Metals

The calcium that's in your bones or in limestone as part of caves, atolls or marble is in the Ca⁺² form, usually bound to CO₃^-2.

Neutral calcium, if mistakenly put in calcium supplements(God forbid), would severely burn your mouth and esophagus as it reacts with water.

Halogens

Neutral fluorine (F₂) is extremely reactive: it is also one the most poisonous of the elements. But fluoride (F^-1) is far less reactive and not as poisonous. In small quantities, fluoride even prevents tooth decay.