Atoms and Bonding

Honours

Revision

A= Nucleus

B = Protons

Neutrons

ElectronsFirst 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 = 2,411 electrons = 2,8,1

Now

Draw an atom of sodium Na23

11

Draw an atom of Chlorine Cl35

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 (H2)

Little 2 shows they are a molecule

Burns with a pop

Zinc + HCl

Water

Methane CH4In natural Gas

Adds to greenhouse

effect

Oxygen O2

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

CovalentLiquids/GasInsoluble in waterDon’t conductLow M.pt & B.ptSlow to react

IonicSolids

Soluble in waterConduct

High M.pt & B.ptFast 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 • Cl2 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)