Atomic structure

An atom is…

The smallest unit of matter that makes up an element

A molecule is…

2 or more atoms chemically bonded together

What are the 3 sub-atomic particles?

Protons

Neutrons

Electrons

What is the relative mass, relative charge & position of protons?

Relative mass: 1

Relative charge: +1

Position: In the nucleus

What is the relative mass, relative charge & position of neutrons?

Relative mass: 1

Relative charge: 0

Position: In the nucleus

What is the relative mass, relative charge & position of electrons?

Relative mass: 1/1836

Relative charge: -1

Position: In electron shells orbiting the nucleus

Describe the structure of an atom

Atoms have a nucleus which contains protons & neutrons

The nucleus is orbited by electrons shells which contain electrons

How many electrons can go into each electron shell?

1st electron shell → 2 electrons

2nd electron shell → 8 electrons

3rd electron shell → 8 electrons

The mass number is…

The total number of protons & neutrons an atom has

The atomic number is

The number of protons at atom has

(number of protons = number of electrons because atoms are neutral)

An isotope is…

Atoms of the same element that have the same number of protons but a different number of neutrons

This means that the atomic number is the same but the mass number is different

How is the relative atomic (A_r) mass calculated?

(isotope A mass × isotope A abundance %) + (isotope B mass × isotope abundance B %) ÷ (total number of atoms)