Midterm- Unit 2 Chemistry: Atomic Structure

Atom

* The building block of all matter


* Smallest unit of an element
* Can not be broken down
* Mostly made of of space

Electron orbital/ cloud

Rings surrounding the nucleus in which the electrons are located in

Atomic number

* Unique to each element
* It equals the number of protons and the number of electrons

Average atomic mass

The abundance of various isotopes of an element

* Calculated by multiplying the atomic mass by its natural abundance of all the isotopes then added them all together

Isotope

An atom of the same element that has a different number of neutrons but the same number of protons. Its atomic mass changes since the number of neutrons change.

Proton

* Atom with positive charge (p+)
* Located in the nucleus
* Mass of 1 AMU
* Determines the identity of an atom

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Neutron

* Atom with neutral charge (n0)
* Mass of 1 AMU
* Holds together the nucleus

Electron

* Atom with negative charge (e-)
* Located in the electron cloud
* Responds for reactivity

Ernest Rutherford

Shot alpha particles through a piece of gold foil and discovered the nucleus

J.J Thomson

* Performed experiments on beams of electricity passed through cathode ray tubes.
* Created the plum pudding/ chocolate chip model of an atom
* Proposed that all atoms have negative electrons in a positive sphere

Democritus

Conceived the idea of matter being made of indivisible particles.

Schrodinger

Proposed that electrons behave as both waves and particles, and their position cannot ever be exactly pinpointed.

Bohr

Compared the movement of electrons to planets orbiting the sun.

Dalton

Discovered that electrons occupy energy levels that they can “jump” between.