Atomic Structure

Bohr model of a helium atom

-An atom consists of a nucleus made of protons and neutrons that is orbited by electrons

Atomic Structure

-The number of protons, not electrons or neutrons, determines the unique properties of an element

-The number of protons is called the element’s atomic number

-Most of the time, the number of protons will be the same as the number of electrons

Atomic Structure-The size of a nucleus is very small (10,000 to 100,000 times smaller than the atom), but the nucleus contains almost all the mass (protons + neutrons).

If the nucleus (1 proton) of a hydrogen atom were as large as the width of a human thumb, the electron would be on the average about a little more than half a mile away with only empty space in between

-The electrons occupy a large area around the tiny nucleus, and this is what determines the size of an atom.

Atomic Structure

Atomic StructureSubatomic Particles

proton electron neutron

Symbol p+ e- n0

Charge +1 -1 0

Mass 1 1/1837 1

Elements on the Periodic Table

Label the four parts of this element.

atomic number

element symbol

element name

atomic weight