Atomic Structure and Bonding. The Structure of Atoms. Specific Learning Outcomes. Describe or label a diagram of a model of an atom using the terms protons, neutrons, electrons and nucleus. Define atomic number (Z) Define mass number (A) Define and give examples of isotopes.
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The Structure of Atoms
In 1806 John Dalton reintroduced the idea of an atom. His theory suggested that all elements were made up of atoms. These atoms were unique to the element and could not be created or destroyed. When atoms from different elements joint together they would form compounds.
Devised the “Chemical Symbol”
First letter uppercase, second letter lower case.
J J Thomson
Discovered a lot more about atomic structure – like polarity and density.
Discovered that some elements existed in combinations atoms like Cl2 or O2
Learnt how to count the positive charges in an atom and how electrons were arranged.
Chemists have a symbolic way of representing atoms which enables them to quickly see how many protons, neutrons and electrons an atom has…
Mass Number =
Number of protons plus neutrons in the nucleus
Atomic Number =
Number of protons in the nucleus or
Number of electrons outside of the nucleus
Atoms of the same element can have different numbers of neutrons; the different possible versions of each element are called isotopes.
For example, the most common isotope of hydrogen has no neutrons at all; there's also a hydrogen isotope called deuterium, with one neutron, and another, tritium, with two neutrons.
What's the most important thing to learn in chemistry?Never lick the spoon.
An electron configuration of an atom is a description of the number of electrons in each energy level.
Whatever is left over
To complete an electron configuration take the atomic number (Z) and spread it out through the levels – each level has a maximum number of electrons that it will hold as demonstrated above.
For example for the element calcium where Z = 20, the electron configuration would be as 2,8,8,2.