Topic 3: Chemistry

Atomic theory

The atomic theory was developed by many people throughout time. The ones that helped develop this theory are: Democritus, Aristotle, Dalton, Thomson, Rutherford, Bohr.

Subatomic particles

The particles the atom is made of. Protons, neutrons, and electrons.

Neutrons

No charge, makes up part of the mass in an atom, located in the nucleus.

Protons

Positive charge, cation, makes up part of the mass in an atom, located in the nucleus.

Electrons

Negative charge, anion, found in the electron cloud(energy levels).

Atomic number

Number of protons. Unique to each atom. #p+ = #e-(except in an ion).

Atomic mass

Composed of neutrons and protons.

Isotopes

Atoms of the same element that have different numbers of neutrons in the nucleus. Mass number is determined by the number of protons and neutrons in the nucleus. Average atomic mass is a mixture of isotopes. Same atomic number, different amounts of neutrons.

Valance electrons

they are located in the outermost shell and are responsible for forming chemical bonds. The number of valence electrons is equal to the group number.

Bohr model

Proposed that electrons move in paths at certain distances around the nucleus. Electrons can jump from a path on one level to a path on another level.

Lewis structure

Electrons of an atom are of two types: core electrons and valence

electrons. Only the valence electrons are shown in Lewis dot-line structures.Shows or represent valence electron as a dot surrounding the element symbol.