Please enable JavaScript.
Coggle requires JavaScript to display documents.
A201 L01 Atoms, All reactions are exothermic - Coggle Diagram
A201 L01 Atoms
ATOMIC STRUCTURE
- Neutron
- Proton (+)
- Electron (-)
- Arrangement of electron: Electron configuration
- inner shell (2) valence shell (8)
- Electrons in inner shells have stronger attraction
Octet rule:
- Atoms have tendency to have 8 outer electrons,
- Atoms will lose, share, gain electrons just to fulfill this rule
- Duplet rule (2 valence electrons, similar)
Isotopes
- Isotope: different neutron no. , same proton & electron no.
- Most elements have 2/more isotopes
Relative atomic mass: (isotope mass X %) + (other isotope mass X %) + ,,,,,
ATOMIC RADIUS
- Increases as group descend
- Moving down the group, increase in valence shells
- Electrons are further and shielded by electron shells
- Outermost shell weaker attraction to nucleus
- Valence electrons not held tightly, increase atomic radius
- Across period, proton no. increase
- Nuclear charge increase
- However, valence shell no. remain constant
- Experience relative similar shielding effect
- Valence electron stronger attraction to nucleus
- Reduce atomic radius
IONIZATION ENERGY
Refers to the removal of 1 mole of valence electron from 1 mole of gaseous atom to produce 1 mole of cation (1+)
Process can repeated,
- however, more energy is needed as atomic radius decrease,
- increasing attraction between electron and nucleus
-
-
ELECTRON AFFINITY
Energy released when 1 mole of electron added to 1 mole of gaseous atom to form 1 mole of anion (1-)
The higher the energy release, the more the affinity (love) for electron
Metal and non-metal:
Metals: lower E.A., easier to lose electron due to low valence electron no.
Non-metals: higher E.A. easier to gain electron, valence electron shell closer to nucleus, easier to attract electron
Across the period, electron affinity increase
- Across period, proton no. increase, while valence shell no. remain
- Increase positive charge and valence electrons have stronger attraction
- Electrons are more attracted to the atom, increase electron affinity
Down the group, electron affinity decrease
- Down the group, increase in valence shells
- Increasing shielding effect due to increase in no.of inner electrons
- Valence electrons have a weaker attraction to nucleus
- Lesser attraction to electrons
GROUP 2 METALS
Alkaline earth metals
- Harder, more dense than grp 1
- Higher BP, MP than grp 1
- Higher I,E,
- Less reactive
- Reactivity increases down the grp
React with non-metals to form ionic compounds, losing 2 electrons (2+)
Ca + Cl --> CaCl
-
-
GROUP 1 METALS
Alkali metals.
- Soft metals
- Low density
- Low BP, MP
- Lowest I.E.
- Higher reactivity
- Reactivity increases down the grp
-
-
All alkali metals react with non-metal to form ionic compound, losing 1 electron (cation 1+)
2Na + Cl2 --> 2NaCl
GROUP 17 HALOGENS
- Diatomic molecules
- High E.A.
- Forms anions (1-)
- Reactivity decreases down the group
- Increase BP, MP down the group
- Increase in colour down the group
-
-
Reacts slowly with water to oxidize water (fluorine & chlorine)
3F2 + 2H2O --> 6HF + O3 (ozone)
Cl2 + H2O --> HCl + HOCl (hypochlorous acid)
GROUP 18 NOBLE GAS
- Completely filled valence electron shell
- High I.E.
- Highly UNREACTIVE
- Inert gas
-