The Modern View of Atomic Structure Section 2.3 The Modern View of Atomic Structure

Three Subatomic Particles Proton Neutron Electron

Proton Positively charged particle Located in the nucleus of the atom Charge of +1.602 x 10-19 C Expressed in multiples of the charge= +1

Electron Negatively charged particle Orbit the nucleus of the atom Account for most of the volume of the atom Charge of -1.602 x 10-19 C Expressed in multiples of the charge = -1

Neutron Uncharged and electrically neutral particle Located in the nucleus of the atom

The Atom

Every atom has an equal number of protons and electrons, and so atoms have no net electrical charge.

Mass of the Atom Expressed in the atomic mass unit (amu) 1 amu = 1.66054 x 10-24 g 1 g = 6.02214 x 1023 amu

Particle Charge Mass (amu) Proton Positive (+1) 1.0073 Neutron None (neutral) 1.0087 Electron Negative (-1) 5.486 x 10-4

Atomic Number References the number of protons in the nucleus of an atom of a particular element Every element has a unique atomic number

Question If Pb has an atomic number of 82, how many protons are in the nucleus of every atom of Pb? How many electrons must be orbiting the nucleus of every Pb atom?

Mass Number Total number of protons plus neutrons in the nucleus of an atom of an element. Uses the number of neutrons in the most abundant form of the element

How many protons? How many electrons? How many neutrons?

Isotopes Atoms with identical atomic numbers but different mass numbers