Download Structure - The Crazy Scientist

Structure 1
Atomic
• Atoms are composed of three sub-atomic particles, one of which (electron) is a
fundamental particle.
E
L
P
• Protons (positive charge) and neutrons (neutral in charge) are located in the
nucleus at the centre of the atom. The nucleus contains 99.95% of an atoms mass
BUT only takes up a small space. (you could fit 100,000 nuclei across the diameter
of an atom)
• Electrons are negative charged particles that are found in descrete regions around
the nucleus called ‘shells’.
• The atomic number (Z) is the number of protons in the nucleus and is what makes one
element different from another element.
• The mass number (A) is the sum of the protons and neutrons in the nucleus.
M
A
S
E
A
Z
Nuclear symbols
A
Z
E
= element
= mass number protons + neutrons)
= atomic number (number of protons)
88
38
Strontium-88 has 38 protons (atomic number), 50 neutrons (atomic mass - atomic number). Since there
is NO charge there must be 38 electrons (same number as protons).
eg Calculate the number of protons, neutrons and electrons in
Sr
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