Oxidation Numbers - An elements position in the periodic table can help us figure out what charge the ion has that they form.
1A family (alkali metals). 1 valence electron, loses an electron to form a cathion with +1 charge.
11A family (alkaline metals). 2 valence electrons, loses two electrons to form a 2+ cathion.
111A family. 3 valence electrons, loses three electrons to form a 3+ cathion.
VA family. 5 valence electrons, gains three to form an anion with a 3- charge.
V1A family. 6 valence electrons, gains two to form an anion with a -2 charge.
V11A family (halogens). 7 valence electrons, gains one for form an anion of -1 charge.
Multiple oxidation states - Some transition metals have multiple oxidation states e.g tin 2 (sn2+) and tin 3 (sn3+).
Polyatomic Ions - A polyatomic ion is composed of two or more atoms.e.g Mercury Ion (Hg2 2+) shows two mercury atoms bonded together. The plus two shows each mercury cathion has a +1 charge.
Compounds which are ionically bonded are commonly known as salts. In sodium chloride, each sodium cation is surrounded by 6 chlorine anions and each chlorine anion is surrounded by 6 sodium cations.
Balancing Charges - To work out the formula of a non-metal and a metal reacting, put the atoms side by side with the metal on the left.
Magnesium for example has 3s2 in its outer shell. This means it must lose two valence electrons to become stable. As a result it will create a cation of +2.
Bromine’s end configuration is 4s2 3d10 4p5 (the 4’s only add upto 7) showing it has 7 valence electrons and needs to gain one to become stable. Once it gains one more atom, it will become a bromide anion with a -1 charge.
Since the magnesium has a +2 charge, it needs 2 bromide anions each with a single negative charge in order to be balanced. The end formula will be MgBr2.
The same can be used to work out polyatomic formulas.e.g the ammonium cation is NH4+ and the sulfide anion is S2-. Two positive ammonium ions are needed to balance the two negative charges on the sulfide ion resulting in (NH4)2S.
Naming Ionic compounds - Write the name of the metal first, then the non-metal and add an -ide ending to the non-metal. e.g lithium and sulfur becomes lithium sulfide.
Rows - Elements in the same period have the same number of atomic orbitals. e.g Every element in the first period has one orbital for its electrons.
Groups - Groups are arranged in columns from top to bottom. Elements in the same group have the same number of electrons in the outer shell. e.g Every element in the first column has one electron in their outer orbital.
Metals - Approx 75% of all elements are metals. They are usually solid at room temperature (except mercury, liquid).
Good conductors of electricity and heat e.g silver (AG) and copper (CU) are two of the best conductors.
Metals are very reactive and form compounds with other elements easily.
Metals react with water to produce bases (hydroxides, OH-) and with acids to produce salts. Sodium Chloride (NaCl) when dissolved in water breaks apart sodium (Na+) and chlorine (Cl-) illustrating metals usually produce positive Ions.
Non-metals - These are usually found on the right of the table. They are usually brittle and are poor conductors of both heat and electricity. Then tend to gain electrons in chemical reactions.
Metalloids - These have properties that are a cross between metals and non-metals. They only partially conduct electricity. Boron, Silicon, Germanium and arsenic are examples.
Electrons furthest away from the nucleus can be gained, lost or shared. Electrons in the outermost energy level are called valance electrons.
Isotopes and Ions
If an element has varying numbers of neutrons, these atoms are then known as isotopes.
Atoms which have unequal numbers or protons and electrons are known as ions.e.g sodium (NA), atomic number 11, is neutral.It has 1 electron on its own spinning in the outer orbital so will give away this electron to make itself stable where possible.
Sodium Ions are represented as Na+ (It has lost one electron) and now contains more positive charges than negative charges. Magnesium Ion is represented as MG2+ as it has lost two electrons.
Electrons which have a positive charge are called Cathions.
Chlorine has 7 electrons in its valence shell, it needs one moer to become stable. By gaining another electron, it has turned negative (more electrons than protons). It is now repesented as Cl-.
Electrons which have a negative charge are called anions.
Ions are commonly found in salt compounds. When salts are dissolved in water they produce solutions which conduct electricity. These substances are known as electrolytes.
If a substance is an electrolyte, the compound is probably ionically bonded. If its a nonelectrolyte, probably covalently bonded.
Ionic Bonds - Where two or more elements transfer electrons.
Covalent Bonds - Where two or more elements share electrons. e.g H2O
Gas to liquid = condensation. (gas particles have a high amount of energy, as they are cooled energy decreases, the particles become closer together forming a liquid).
Liquid to Gas = Boiling (heating a liquid allows particles to absorb heat, they move faster to forma gas).
liquid to solid = Freezing (Energy decreases by cooling, the particles move closer together to form a solid).
Solid to liquid = Melting (heating a solid makes particles in the crystal lattice break free to form a liquid).
Sublimation = Solid to Gas skipping the liquid stage. e.g dry ice CO2(s)
Deposition = Gas to solid state skipping the liquid stage.
Matter can be divided into pure substances or mixtures.
Pure substances - Can either be an element or a compound
Mixtures - Made up of two or more substances.Easy to seperate. e.g through filtration. Mixtures can be heterogeneous (can easily see the different parts) or homogeneous (cannot easily see the different parts).
Elements - Are composed of a single type of atom.
Atom - Smallest particle of an element.
Compounds - composed of two of more elements in a specific ratio.e.g Water is made up on hydrogen and oxygen in a 2:1 ratio.
“The meeting of two personalities is like the contact of two chemical substances: if there is any reaction, both are transformed.” - Carl Jung
