Atoms and Bonding Honours

Revision A=Nucleus B =Protons Neutrons Electrons First Shell Second Shell C = D = E = F =

C 12 6 Mass Number Atomic Number

Drawing Atoms How many protons? Atomic Number The small number How many electrons? Same as protons. How many neutrons? Subtract small from large Mass Number – Atomic Number tells us how many neutrons.

Drawing Atoms 1. Write down how many protons, electrons, neutrons. 2. Give out the electrons. 3. Draw the nucleus (put in protons & neutrons) 4. Draw in electrons – ones then double up 5.Check – number of dots = small number

Electrons Max of 2 in first shell Max of 8 in all the rest. So “give out” the electrons like this 6 electrons = 2,4 11 electrons = 2,8,1

Now Draw an atom of sodium Na Draw an atom of Chlorine Cl 35 17

Sodium and Chlorine

Plus and Minus attract each other Extra electron brings extra minus charge Both ions have FULL outside shell– they are STABLE

Ionic Bonds formed

Magnesium & Oxygen

Mg and O Mg + 0  MgO Burn Mg in oxygen gas White light White powder formed is MgO MgO turns litmus blue --- base

Ionic Bond Is the force of attraction Between oppositely charged ions E.g. Na + Cl - bond to form NaCl

Ionic Compounds Solids at room temp. High melting points and boiling points Soluble in water Conduct electricity when molten or dissolved (as the ions can move and carry charge) Fast reactions Formed between left and right of PTE

RESULT Bulb lights Conclusion Liquid conducts elec. (or opposite)

Covalent Bond Atoms SHARE at least one pair of electrons Become STABLE as they have FULL outside shell

Hydrogen (H 2 ) Little 2 shows they are a molecule Burns with a pop Zinc + HCl

Water

Methane CH 4 In natural Gas Adds to greenhouse effect

Oxygen O 2 Double Bond – 2 pairs shared electrons

Oxygen Carried by red blood cells (haemoglobin) Used in respiration To release energy from food (all cells) MADE by plants in photosynthesis MADE in lab – hyd.per and manganese dioxide Taken in by animals and out by plants Neutral gas Supports combustion

Covalent Compounds Liquids or gases Low melting points and boiling points Insoluble in water Do NOT Conduct electricity when molten or dissolved (as the ions can move and carry charge) Slow reactions

Compare Covalent Liquids/Gas Insoluble in water Don’t conduct Low M.pt & B.pt Slow to react Ionic Solids Soluble in water Conduct High M.pt & B.pt Fast to react

PERIODIC TABLE Group One (Li, Na, K) Alkali Metals One electron in outer shell – valency =one Form positive ions – give electron away Highly reactive – water Stored under oil

Alkali Metals Same structure =same properties React with water sodium + water  sodium hydroxide + hydrogen gas xxxxxx + water  ……. Hydroxide + hydrogen gas React with air Tarnish Form sodium oxide ( or lithium oxide etc)

Group Two Alkaline Earth Metals Two electrons in outer shell Valency of 2

Group 8 Halogens Seven electrons in outer shell Valency = one Cl 2 and F ions in water treatment Group 7 Noble Gases Eight electrons in outer shell Valency = zero STABLE Unreactive (role model for all the others – they want to be like nearest Noble gas)