Inside an AtomInside an Atom

All All mattermatter is made up of one or more is made up of one or more elementselements

ElementElement: substance that cannot be broken : substance that cannot be broken down into smaller substancesdown into smaller substances

Examples: Hydrogen, Carbon, Examples: Hydrogen, Carbon, OxygenOxygen

AtomAtom: the smallest unit of an element: the smallest unit of an element

Parts of an AtomParts of an Atom

ProtonProton – positive charge (+) – positive charge (+)

NeutronNeutron – neutral (no charge) – neutral (no charge)

ElectronElectron – negative charge (-) – negative charge (-)

Protons and neutrons are found in the Protons and neutrons are found in the nucleusnucleus in the center of the atom in the center of the atom

Electrons are moving rapidly in a Electrons are moving rapidly in a cloud around the nucleuscloud around the nucleusDifferent energy levels around the nucleusDifferent energy levels around the nucleusElectrons may “hang out” in these levelsElectrons may “hang out” in these levelsValence electronsValence electrons – those that are farthest – those that are farthest

from the nucleus and most loosely heldfrom the nucleus and most loosely held

Properties of AtomsProperties of Atoms

An atom is An atom is neutralneutral when it has an equal when it has an equal number of protons (+) and electrons (-).number of protons (+) and electrons (-).

Sometimes when one atom reacts with Sometimes when one atom reacts with another atom, it gains or loses an electron another atom, it gains or loses an electron giving it a positive or negative chargegiving it a positive or negative charge

This charged particle is called an This charged particle is called an IONION

If an atom loses an electron (-), it now If an atom loses an electron (-), it now has a positive charge (cation)has a positive charge (cation)

If an atom gains an electron (-), it now If an atom gains an electron (-), it now has a negative charge (anion)has a negative charge (anion)

Properties continued…Properties continued…

More PropertiesMore Properties

Atomic NumberAtomic Number – number of protons – number of protonsIdentifies and determines the elementIdentifies and determines the element

Carbon: atomic # 6Carbon: atomic # 6 Sodium: atomic # 11Sodium: atomic # 11 Gold: atomic # 79Gold: atomic # 79

Atomic massAtomic mass – average mass of one – average mass of one atom of an elementatom of an element

Atomic Mass Unit (Atomic Mass Unit (amuamu))

SI unit used to measure the mass of SI unit used to measure the mass of particles in atomsparticles in atoms

Protons and Neutrons = 1 amuProtons and Neutrons = 1 amuApproximately 2000 Electrons = 1 amuApproximately 2000 Electrons = 1 amu

Almost all of an atom’s mass is in the Almost all of an atom’s mass is in the nucleusnucleus

IsotopesIsotopes

The number of protons for a certain The number of protons for a certain atom never changes, but sometimes atom never changes, but sometimes an atom may have different numbers an atom may have different numbers of neutronsof neutrons

Mass NumberMass Number – sum of protons and – sum of protons and neutronsneutrons

Hydrogen IsotopesHydrogen Isotopes