Cutting edge science In Aristotle’s times: 4 elements.

Prior to that there was an opinion that there is only 1 element – water.

Everything in the world must be made of water:

•Living things all need it – water is part of them, they are made of water!

•Nonliving things must also originate from water. The proof is in the stream!

•Elements

•Compounds

Physical stateSolidLiquidGas

Chemical reactivityEnergy

•Physical state and chemical reactions

LIFE IN THE ELECTRON CITYNAME: Valence Electron

City Ordinance (from * to ****)*NEIGHBORHOOD: Principle Energy Level (PEL): n

n = 1, 2, 3, 4**STREET: Energy Sublevels (ES): s, p, d, f***HOUSES: Orbitals – their number is “not negotiable”:

f = 7d = 5

p = 3s = 1

Electrons must occupy sublevels in a particular order. The lowest energy sublevel “s’ is occupied first, then “p”, then “d”, then “f”.

Not every PEL has all four sublevels on it. In fact, n = 1 has only “s”, n = 2 has “s” and “p”, n = 3 has “s”, “p” and “d”; only n = 4 has is all!

And here is why there is such a strict “city ordinance” about how many “houses”/orbitals can be on each sublevel:

The shape of the orbital determines how many electrons can “comfortably” occupy it. Low energy sublevels havefewer orbitals.

Empty orbitals are like vacant electron houses.

****Each orbital can fit only 2 electrons. The maximum of electrons is shown as a superscript notation above the orbital:

s2 p6 d10 f14

Nature is a no-nonsense city manager.The order of occupancy is determined by above mentioned rules: from n = 1 to n = 4 from s to f.

The final city ordinance is this: *****the street must be all occupied or all empty,

with a contradiction written in: single electrons must first occupy all available

“houses” (orbitals), before they are “allowed” to have a partner.

Have your heard of the workplace “rule” – last to come – first to go? It applies to electrons too.

After the more favorable - low energy sublevels have been occupied, the remaining electrons are

sent to the higher PEL, where they become Valence Electrons. They are the electrons that

can be “shared” or “spared” to comply with the “all street empty” or “all street full” rules. The PEL position determines weather the electron

will be used to “attract” another atom’s electron to “fill” the orbital or to “sent away” to vacate the

street where this lonely electron would have been the sole tenant:

H and Li need to give away an e־.F need to take one.He and Ne are in the Golden age - they have completed the outer layer and have no valence e־ in need for a change.

Now you can see why periodic table has uneven distribution of elements depending on PEL (PEL is represented as Period #) and why there are empty spaces in the first three periods.

F (halogen) with atomic number 9 has electron notation only one electron away from Ne By taking electron from another atom it can “fool” itself into “completeness”.All halogens (group VIIA) have the same electron configuration and the same chemical properties – they are “extreme takers”.

On the other side of the table Na and Li is also one step away from Ne. But what a huge step!To become “like the nobles”, they needs to give away the outer layer electron. They are “extreme donors”.

Be with atomic number 4 gives away 2 of the outer layer electrons to become positively Charged Be2+ - cation

O with atomic number 8 has an empty orbital on p sublevel.It is taking 2 electrons to become negatively charged O2- - anion.

Positively charged Be2+ and negatively charged O2- formneutral compound beryllium oxide: BeO.

Same happens when Li and Br enter into reaction. Resulting compound is called an ionic solid. Ionic solid dissolve in water produce the very same cation and anions that formed them.

Even though we often hear: “a molecule of salt” mentioned, the salts are not composed of molecules, but of ionic compounds. LiBr, NaCl, KCl are some examples. There is no easy way to determine that a material is a salt from its chemical formula, like you can with an acid or a base. Bases have the OH term in the end of their chemical formula (NaOH).Acids usually have an H at the start of the formula (HCl).

Salts normally do not have either the OH or the H terms.

Salts can be formed by several chemical reactions:

1. By exposure of active metal to active non-metal: 2K + Cl2 = 2KCl

2. By active metals reacting with active acid (at least one of them should be active): Zn + 2HCl = ZnCl2 + H2

3. By replacing one metal with another more active in the salt: Ni + 2AgNO3 = Ni(NO3) + 2Ag↓

4. By exchange between 2 salts: Ag2SO4 + 2NaCl = Na2SO4 + 2AgCl

5. By neutralization (acid-base reaction): Al(OH)3 + 3HI = AlI3 + 3H2O

Salt can be transformed into one another under heating:

KClO3 =>KCl + O2

Examples of Acids

Aqua Regia contains concentrated Nitric acid and concentrated Hydrochloric acid in the ratio 1:3. Aqua Regia means 'Royal Water' in Latin. It is used to dissolve noble metals like gold and platinum.

Milk contains lactic acid. It is named after the Latin word 'lac', which means milk.

Vinegar is very dilute acetic acid. The vinegar used in cooking contains approximately 4% of acid.The chemical formula of acetic acid is CH3COOH.

Sulfuric acid is used in the manufacture of many car batteries. It is also known as 'Oil of Vitriol'. The chemical formula of Sulfuric acid is H2SO4.

Carbonic acid is responsible for the 'fizz' in soft drinks. It decomposes into Carbon dioxide bubbles. The chemical formula of Carbonic acid is H2CO3.

Ascorbic acid is the chemical name of Vitamin C. The chemical formula of ascorbic acid is C6H8O6.

Acid Defined:

Arrhenius definition: acids form hydrogen ions (H+) in aqueous solution.

Brønsted-Lowry definition: acids donate hydrogen ions H+.

Lewis definition: an acid reacts with a base by forming a new covalent bond utilizing an empty orbital of the acid to share the extra electron pair of the base.[by this definition very far-reaching conclusions may be made, defining anything that accepts negatively charged particles as “acid”.]