Chemistry - Atomic Structure

Atom

A tiny particle that makes up matter, made up of subatomic particles called neutrons, protons and electrons

Proton

the positive charge which has a relative mass of 1 (in nucleus)

Neutron

Has no electric charge but a mass of 1 (in nucleus)

Electron

has a negative electric charge and has a relative mass of 1/2000 (1837 electrons to equal the mass of a proton/neutron) orbits the nucleus

Element Symbols

Short forms are used to represent the names of the elements— The first letter is always UPPER case and the second is always lower case (ex., Calcium - Ca)

Atomic Number

• the atomic number of an element can be found on the periodic table; it identifies the element

• the atomic number = number of protons

Atomic Mass

• the sum of protons and neutrons in an atom

• can be found on the periodic table

Number of Neutrons

number of neutrons = atomic mass − atomic number

Standard Atomic Notation

Standard atomic notation shows mass number (top left) and atomic number (bottom left):

_mass^​

_^atomic Symbol