Atoms

ATOMS

→ the smallest mediaeval unit of time, equal to fifteen ninety-fourths of a second.

→ a theoretical particle of matter, imagined to be incapable of further division; the smallest possible unit of substance.

Sub-atomic Particles:

Protons:

→ a positively charged subatomic particle forming part of the nucleus of an atom → determines the atomic number of an element.

Electron:

→ the subatomic particle having a negative charge

→ orbiting the nucleus; the flow of electrons in a conductor constitutes electricity.

Neutron:

→ subatomic particle forming part of the nucleus of an atom

→ no charge.

How to Determine the Atomic and Mass Number:

• Atomic Number

→ number of protons in the nucleus of an atom determines an element's atomic number

• Mass Number

→ determined by the number of protons and neutrons in an atom

Ex:

* Isotope - Any of two or more atoms of an element having the same number of protons, but a different number of neutrons in its nucleus. (same atomic number but not mass number)

Ex:

IONS

→ an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge

• Anion – gains electrons (negative)

Ex:

• Cation - loses electrons (positive)

Ex:

AZPEN*

Formula:

• A (mass number) = P + N

• Z (atomic number) = P

• P (proton) = Z

• E (electrons) = P - [charge of ion]

• N (neutron) = A - Z