Intro to Atoms & The Periodic Table

The Simplest form of a pure substance

​The smallest particle of an element that retains the chemical properties of an element.

​The atomic mass unit (amu) is used to mass atoms and equals 1.67 x 10-27  Kg

• ​The atom is composed of three subatomic particles

• ​Particles which are smaller than the atom

​Charge: +1 

​

Mass: 1 amu 

​

Location: In Nucleus

​Charge: -1 

​

Mass: 1/1836 amu ~ 0 amu

​

Location: Orbits nucleus in electron cloud

​Charge: 0 (neutral) 

​

Mass: 1 amu 

​

Location: In nucleus

The periodic table tells us important information about elements and atoms that make up elements.​

​The elements are numbered with whole numbers in order. 

​Atomic number always equals the number of protons in an atom.

This means that the protons are also used as the ID of an element

​

​The other number found on the periodic table is the atomic mass

The mass of an atom of the element

​Because the mass of an electron is so small

We can assume that the atomic mass is equal to the number of protons and neutrons.

​The mass number is the atomic mass rounded to the nearest whole number

​# of protons = Atomic number 

• # of electrons = # of protons = Atomic number

• # of neutrons = mass # - Atomic #  

* Mass #- rounded atomic mass (whole #)