Elodie Commissaris
ATOMIC STRUCTURE
> atom = basic unit of an element
>atoms contain subatomic particles (protons, neutrons + electrons):
1. Protons:
- +ve charge
- in nucleus
- relative mass = 1 protons + neutrons are the heavier
subatomic particles which both stay in
- contribute to mass of atom the nucleus and contribute to mass of an
atom ∴ the mass is concentrated @ the
2. Neutrons: nucleus.
- no charge no. of protons + neutrons = mass
- in nucleus number/nucleon number
- relative mass = 1
- contribute to mass of atom
no. of electrons = no. of protons
∴ atom is electrically neutral
3. Electrons:
- -ve charge
- in shells/orbitals
- relative mass = 1/2000
- insignificant mass which doesn’t have an effect on the mass of an atom
- only subatomic particle that moves (due to small mass)
ELECTRONIC CONFIRGURATION
(electronic structure)
= arrangement of electrons in an atom
>innermost shell can accommodate max. 2 electrons
>2nd shell = max. 8 electrons
>3rd shell = max. 8 electrons
, Elodie Commissaris
CHARGING ATOMS
>atoms can be charged either by gaining or losing electrons forming ions (=charged particles)
>when an atom gains electrons it will become negatively
charged
>when an atom loses electrons it becomes positively
charged
MASS NUMBER - ATOMIC NUMBER = NO. OF NEUTRONS
>isotopes = atoms of the same element w/different mass no. (due to different no. of neutrons)
eg.
>isotopes have same chemical properties because only electrons take part in chemical
reactions (not neutrons)
PERIODIC TABLE
=list of elements according to their proton numbers
>atomic number determines position of element on periodic table
>sections left to right are “periods”
period = no. of shells an atom has, atom w/same no. of shells are in same period
eg: 2,8,8,1 —> 4 shells ∴ in period 4
>downward columns are “groups”
group = same no. of electrons in outer shell
eg: 2,8,8,1 —> 1 valence electron ∴ in group 1
>elements in Group 8 (0) are “noble gases”. They have a full outer shell ∴ very stable +
unreactive
>atoms react to achieve a full outer shell making them more stable (usually through bonding)
ATOMIC BONDING
= chemical joining of atoms to form compounds/molecules
Types of bonding:
1. ionic bonding
2. covalent bonding
1. IONIC BONDING
(electrostatic bonding)
>involves transference of electrons from metal to non-metal
, Elodie Commissaris
>results in formation of oppositely charged ions which attract each other by electrostatic forces
>these forces constitute an ionic bond
eg: in the formation of NaCl —> Na (2,8,1) loses its outer shell
electron to form Na+ (2,8). The electron that has been lost is
gained by Cl (2,8,7) to form Cl- (2,8,8). The Na+ and Cl- attract
each other by electrostatic forces forming an ionic bond
>characteristics of ionic compounds:
- soluble in H20 (ions easily hydrated)
- conduct when in solution/molten (not when solid) - ions become free in solution/molten
- high m.p. and b.p. due to high strength of ionic bond
- mostly solids @ r.t.p
2. COVALENT BONDING
>occurs among non-metals
>involves sharing of electrons so that each atom will gain a full outer shell
>the no. of electrons needed by an atom for it to acquire a full outer shell is what it makes
available for sharing
>a single pair of electrons constitutes a single bond
eg: hydrogen (H2) H-H
water (H20) H-O-H
nitrogen (N2) N≡N
>characteristics of covalent molecules:
- weak bonds
- low m.p. and b.p.
- mainly gases/liquids @ r.t.p
- don’t conduct electricity
METALLIC BONDING
>bonding in metals
>lattice of +ve ions in a “sea” of delocalised electrons
>the presence of delocalised electrons enable metals to conduct
electricity
>the +ve ions are of uniform size and are regularly arranged
>when hammered, the uniformly sized ions can easily slip/slide over
each other forming a sheet (malleable)
>when stretched, the ions form a wire (ductile)
, Elodie Commissaris
>alloys = mixture of metals with different sizes of +ve ions. This non uniformity disrupts the
order or the lattice of +ve ions making them uneasy to slide over each other when hammered/
stretched
> ∴ alloys are brittle not malleable or ductile
**brass = copper + zinc
**bronze = copper + tin
GIANT MOLECULAR STRUCTURES
>carbon has 2 allotropes - carbon diamond + carbon graphite
DIAMOND
>each carbon atom is surrounded by 4 other carbon atoms
>very hard ∴ used in drilling and glass + graphite cutting
GRAPHITE
>carbon atoms are arranged in hexagonal layers which are held
together by weak forces with a “sea” of delocalised electrons in-
between which enable graphite to conduct electricity
>the layers can easily slide over each other and peel off ∴ graphite is
used as a lubricant or in pencils
STOICHIOMETRY
=quantitive aspect of chemistry
RELATIVE ATOMIC MASS (Ar) = mass of 1 mole as compared to 1/12 of carbon-12
>equivalent to the mass no. of an atom
RELATIVE MOLECULAR MASS (Mr) = mass of 1 mole of a molecule/compound as compared to
1/12 of carbon-12
>calculated by adding up the Ar values of the individual atoms which are up a compound
eg: Mr of H2SO4 = 2 x Ar(H) + Ar(S) + 4 x Ar(O)
= 2 + 32 + 64
= 98g/mol
MOLES
= the amount of a substance that contains 6.023 x 1023 particles
>this number is referred to as Avogadro’s Constant
ATOMIC STRUCTURE
> atom = basic unit of an element
>atoms contain subatomic particles (protons, neutrons + electrons):
1. Protons:
- +ve charge
- in nucleus
- relative mass = 1 protons + neutrons are the heavier
subatomic particles which both stay in
- contribute to mass of atom the nucleus and contribute to mass of an
atom ∴ the mass is concentrated @ the
2. Neutrons: nucleus.
- no charge no. of protons + neutrons = mass
- in nucleus number/nucleon number
- relative mass = 1
- contribute to mass of atom
no. of electrons = no. of protons
∴ atom is electrically neutral
3. Electrons:
- -ve charge
- in shells/orbitals
- relative mass = 1/2000
- insignificant mass which doesn’t have an effect on the mass of an atom
- only subatomic particle that moves (due to small mass)
ELECTRONIC CONFIRGURATION
(electronic structure)
= arrangement of electrons in an atom
>innermost shell can accommodate max. 2 electrons
>2nd shell = max. 8 electrons
>3rd shell = max. 8 electrons
, Elodie Commissaris
CHARGING ATOMS
>atoms can be charged either by gaining or losing electrons forming ions (=charged particles)
>when an atom gains electrons it will become negatively
charged
>when an atom loses electrons it becomes positively
charged
MASS NUMBER - ATOMIC NUMBER = NO. OF NEUTRONS
>isotopes = atoms of the same element w/different mass no. (due to different no. of neutrons)
eg.
>isotopes have same chemical properties because only electrons take part in chemical
reactions (not neutrons)
PERIODIC TABLE
=list of elements according to their proton numbers
>atomic number determines position of element on periodic table
>sections left to right are “periods”
period = no. of shells an atom has, atom w/same no. of shells are in same period
eg: 2,8,8,1 —> 4 shells ∴ in period 4
>downward columns are “groups”
group = same no. of electrons in outer shell
eg: 2,8,8,1 —> 1 valence electron ∴ in group 1
>elements in Group 8 (0) are “noble gases”. They have a full outer shell ∴ very stable +
unreactive
>atoms react to achieve a full outer shell making them more stable (usually through bonding)
ATOMIC BONDING
= chemical joining of atoms to form compounds/molecules
Types of bonding:
1. ionic bonding
2. covalent bonding
1. IONIC BONDING
(electrostatic bonding)
>involves transference of electrons from metal to non-metal
, Elodie Commissaris
>results in formation of oppositely charged ions which attract each other by electrostatic forces
>these forces constitute an ionic bond
eg: in the formation of NaCl —> Na (2,8,1) loses its outer shell
electron to form Na+ (2,8). The electron that has been lost is
gained by Cl (2,8,7) to form Cl- (2,8,8). The Na+ and Cl- attract
each other by electrostatic forces forming an ionic bond
>characteristics of ionic compounds:
- soluble in H20 (ions easily hydrated)
- conduct when in solution/molten (not when solid) - ions become free in solution/molten
- high m.p. and b.p. due to high strength of ionic bond
- mostly solids @ r.t.p
2. COVALENT BONDING
>occurs among non-metals
>involves sharing of electrons so that each atom will gain a full outer shell
>the no. of electrons needed by an atom for it to acquire a full outer shell is what it makes
available for sharing
>a single pair of electrons constitutes a single bond
eg: hydrogen (H2) H-H
water (H20) H-O-H
nitrogen (N2) N≡N
>characteristics of covalent molecules:
- weak bonds
- low m.p. and b.p.
- mainly gases/liquids @ r.t.p
- don’t conduct electricity
METALLIC BONDING
>bonding in metals
>lattice of +ve ions in a “sea” of delocalised electrons
>the presence of delocalised electrons enable metals to conduct
electricity
>the +ve ions are of uniform size and are regularly arranged
>when hammered, the uniformly sized ions can easily slip/slide over
each other forming a sheet (malleable)
>when stretched, the ions form a wire (ductile)
, Elodie Commissaris
>alloys = mixture of metals with different sizes of +ve ions. This non uniformity disrupts the
order or the lattice of +ve ions making them uneasy to slide over each other when hammered/
stretched
> ∴ alloys are brittle not malleable or ductile
**brass = copper + zinc
**bronze = copper + tin
GIANT MOLECULAR STRUCTURES
>carbon has 2 allotropes - carbon diamond + carbon graphite
DIAMOND
>each carbon atom is surrounded by 4 other carbon atoms
>very hard ∴ used in drilling and glass + graphite cutting
GRAPHITE
>carbon atoms are arranged in hexagonal layers which are held
together by weak forces with a “sea” of delocalised electrons in-
between which enable graphite to conduct electricity
>the layers can easily slide over each other and peel off ∴ graphite is
used as a lubricant or in pencils
STOICHIOMETRY
=quantitive aspect of chemistry
RELATIVE ATOMIC MASS (Ar) = mass of 1 mole as compared to 1/12 of carbon-12
>equivalent to the mass no. of an atom
RELATIVE MOLECULAR MASS (Mr) = mass of 1 mole of a molecule/compound as compared to
1/12 of carbon-12
>calculated by adding up the Ar values of the individual atoms which are up a compound
eg: Mr of H2SO4 = 2 x Ar(H) + Ar(S) + 4 x Ar(O)
= 2 + 32 + 64
= 98g/mol
MOLES
= the amount of a substance that contains 6.023 x 1023 particles
>this number is referred to as Avogadro’s Constant
