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Atomic Structure
4.4.1 Atoms and isotopes
Structure and Model of the Atom:
Atom: a particle with no overall charge. (radius of about 1 x
10^-10, nucleus’ radius is 1/10000th size of that)
Isotope: atoms of an element with the same number of protons but
a different number of neutrons (so different masses).
Isotopes share the same atomic number (identity), may have
different charges if ionized, and always differ in mass due
to their neutron count.
Ion: a charged particle.
The number of protons is called the atomic number
The number of nucleons (is a proton or neutron) is called the
mass number
Protons - +1 charge, mass of 1 and found in nucleus
Atomic Structure 1
, Neutrons - 0 charge, mass of 1 and found in nucleus
Electrons - -1 charge, mass is negligible and found in shells
around nucleus
Basic structure of atom:
Nucleus: At the centre of the atom lies the nucleus, which
contains:
Protons (positively charged)
Neutrons (neutral)
Electron Shells: Surrounding the nucleus are electrons
(negatively charged) that orbit in defined energy levels or
shells.
Absorption: When an atom absorbs energy (like light), an
electron gains that energy and jumps to a higher energy level
—further away from the nucleus.
Emission: When the electron falls back to a lower energy
level, it releases energy in the form of electromagnetic
radiation (often visible light).
Discovery of the model of the atom:
1. Dalton - Assumed that they were tiny spheres that could be
divided.
2. J.J Thomson (PLUM PUDDING MODEL) - discovered the electron.
Atoms are balls of positive mass embedded with negative
electrons.
3. Rutherford (NUCLEAR MODEL) - after discovering alpha
particles (helium nucleus 2+) he fired them at thin gold
foil.
His observations and conclusions:
Atomic Structure 2
Atomic Structure
4.4.1 Atoms and isotopes
Structure and Model of the Atom:
Atom: a particle with no overall charge. (radius of about 1 x
10^-10, nucleus’ radius is 1/10000th size of that)
Isotope: atoms of an element with the same number of protons but
a different number of neutrons (so different masses).
Isotopes share the same atomic number (identity), may have
different charges if ionized, and always differ in mass due
to their neutron count.
Ion: a charged particle.
The number of protons is called the atomic number
The number of nucleons (is a proton or neutron) is called the
mass number
Protons - +1 charge, mass of 1 and found in nucleus
Atomic Structure 1
, Neutrons - 0 charge, mass of 1 and found in nucleus
Electrons - -1 charge, mass is negligible and found in shells
around nucleus
Basic structure of atom:
Nucleus: At the centre of the atom lies the nucleus, which
contains:
Protons (positively charged)
Neutrons (neutral)
Electron Shells: Surrounding the nucleus are electrons
(negatively charged) that orbit in defined energy levels or
shells.
Absorption: When an atom absorbs energy (like light), an
electron gains that energy and jumps to a higher energy level
—further away from the nucleus.
Emission: When the electron falls back to a lower energy
level, it releases energy in the form of electromagnetic
radiation (often visible light).
Discovery of the model of the atom:
1. Dalton - Assumed that they were tiny spheres that could be
divided.
2. J.J Thomson (PLUM PUDDING MODEL) - discovered the electron.
Atoms are balls of positive mass embedded with negative
electrons.
3. Rutherford (NUCLEAR MODEL) - after discovering alpha
particles (helium nucleus 2+) he fired them at thin gold
foil.
His observations and conclusions:
Atomic Structure 2
