Chemistry Summary
Unit 1
Energy levels: specific distances from the nucleus
corresponding to the energy of the electrons
Experiments with subatomic particles
Electrons: very light, negatively charged.
They are deflected more than p+
because of their small mass. Attracted to
the positive pole
Neutrons: neutral
Protons: heavy, positively charged.
Attracted to the negative pole.
Charge of e-: 1.602 x 10-19 C
Mass of e-: 9.109 x 10-21 kg
Plum pudding: e- were seen as being randomly
distributed in a sphere of positive charge
Conclusions made
Mass Relative mass Charge Relative charge
Proton 1.6 x 10-27 1 1.602 x 10-19 +1
Neutron 1.6 x 10-27 1 0 0
Electron 9.109 x 10-21 1/1836 1.602 x 10-19 -1
,Periodic table notation
Atomic Number (Z): number of protons and e-; position in
the Periodic table
Nucleon/Mass Number (A): number of particles in the
nucleus; protons + nucleus
Isotopes
Atoms of the same element with same mass/proton numbers, but different
neutron/nucleon number
Chemical Properties Physical Properties
Isotopes of the same element have the Isotopes have different number of
same chemical characteristics because neutrons, which are neutral but still
they have the same e- number in their add mass to the atom
outer shells
e- are the ones that take part in n are the ones that influence the
chemical reactions and therefore physical properties such as mass and
determine the chemistry of an atom density, due to their mass
, Unit 2
Electron shells
e- form the outer part of the atom, and are only involved in changes during
chemical reactions
● Bohr and Plank proposed that e- could only possess energy quanta, and
could only exist in a stable way when in shells
● Quantum numbers (n): number of rows in periodic tables
Energy shell Max e- number
1 2
2 8
3 18
4 32
5 50
However, these models are simple, so they can be divided into subshells
● The region where an electron is most likely to be found is an orbital
● They can be divided into 4 types: s, p, d and f (where each one has its own
characteristic shapes)
e- number of orbitals types of orbitals
n=1 2 1 s
n=2 8 4 s, p(px,py,pz)
n=3 18 9 s, p, d
n=4 32 18 s, p, d, f
s orbitals
*Spherical shape
*Their size increases with
increasing shell number
p orbitals
● Dumbbell shape
● Their lobes become larger
and longer with increasing
shell number
, ● s orbitals: maximum 2 e-
● p orbitals: maximum 6 e-
● d orbitals: maximum 10e-
Energy level max e- number
1st 2
2nd 8
3rd 18
Box notation
The e- in Titanium. e- occupy the
lowest energy levels first before filling
those with higher energy.
- The e- are represented by
opposite arrows to show their spin
- The boxes are arranged in
order of increasing energy, from
lowest to highest
● Group 1: s1
● Group 17: p5
Unit 1
Energy levels: specific distances from the nucleus
corresponding to the energy of the electrons
Experiments with subatomic particles
Electrons: very light, negatively charged.
They are deflected more than p+
because of their small mass. Attracted to
the positive pole
Neutrons: neutral
Protons: heavy, positively charged.
Attracted to the negative pole.
Charge of e-: 1.602 x 10-19 C
Mass of e-: 9.109 x 10-21 kg
Plum pudding: e- were seen as being randomly
distributed in a sphere of positive charge
Conclusions made
Mass Relative mass Charge Relative charge
Proton 1.6 x 10-27 1 1.602 x 10-19 +1
Neutron 1.6 x 10-27 1 0 0
Electron 9.109 x 10-21 1/1836 1.602 x 10-19 -1
,Periodic table notation
Atomic Number (Z): number of protons and e-; position in
the Periodic table
Nucleon/Mass Number (A): number of particles in the
nucleus; protons + nucleus
Isotopes
Atoms of the same element with same mass/proton numbers, but different
neutron/nucleon number
Chemical Properties Physical Properties
Isotopes of the same element have the Isotopes have different number of
same chemical characteristics because neutrons, which are neutral but still
they have the same e- number in their add mass to the atom
outer shells
e- are the ones that take part in n are the ones that influence the
chemical reactions and therefore physical properties such as mass and
determine the chemistry of an atom density, due to their mass
, Unit 2
Electron shells
e- form the outer part of the atom, and are only involved in changes during
chemical reactions
● Bohr and Plank proposed that e- could only possess energy quanta, and
could only exist in a stable way when in shells
● Quantum numbers (n): number of rows in periodic tables
Energy shell Max e- number
1 2
2 8
3 18
4 32
5 50
However, these models are simple, so they can be divided into subshells
● The region where an electron is most likely to be found is an orbital
● They can be divided into 4 types: s, p, d and f (where each one has its own
characteristic shapes)
e- number of orbitals types of orbitals
n=1 2 1 s
n=2 8 4 s, p(px,py,pz)
n=3 18 9 s, p, d
n=4 32 18 s, p, d, f
s orbitals
*Spherical shape
*Their size increases with
increasing shell number
p orbitals
● Dumbbell shape
● Their lobes become larger
and longer with increasing
shell number
, ● s orbitals: maximum 2 e-
● p orbitals: maximum 6 e-
● d orbitals: maximum 10e-
Energy level max e- number
1st 2
2nd 8
3rd 18
Box notation
The e- in Titanium. e- occupy the
lowest energy levels first before filling
those with higher energy.
- The e- are represented by
opposite arrows to show their spin
- The boxes are arranged in
order of increasing energy, from
lowest to highest
● Group 1: s1
● Group 17: p5
