2REVIEW ATOMSAtomAn atom is the smallest particle of an element that still has the properties of that element50 million atoms, lined up end-to-end = 1 cmAn atom = proton(s) + neutron(s) + electron(s)The Greek root for the word atom, "atomon," means "that which cannot be divided.”
3The structure of the atom The Ancient Greeks used to believe that everything was made up of very small particles. Some experiments in 1808 proved this and called these particles ATOMS:ELECTRON – negative, mass nearly nothingPROTON – positive, same mass as neutron (“1”)NEUTRON – neutral, same mass as proton (“1”)
5The Atom Hydrogen: Proton Electron Hydrogen has one proton, one electron and NO neutrons
6The Atom Sodium Valence Shell Electrons Protons Neutrons Sodium has eleven electrons, eleven protons and twelve neutrons.
7area surrounding the nucleus Atomic Theory:Atoms are made up of smaller particles known as sub-atomic particles.The nucleus is at the center of an atom.The nucleus is composed of protons and neutrons.Electrons exist in the space surrounding the nucleus.# of protons = # of electrons in every atomNuclear charge = charge on the nucleus = # of protonsAtomic number = # of protons = # of electronsNameSymbolChargeLocationRelative MassProtonp1+nucleus1836NeutronnElectrone1–area surrounding the nucleus1See page 170
8Mass and atomic number 4 He 2 Particle Relative Mass Relative Charge Proton1NeutronElectron-1MASS NUMBER = number of protons + number of neutronsHe24SYMBOLATOMIC NUMBER = number of protons (obviously)
9Subatomic ParticlesGroup 1Element symbol1 HHydrogen1.001Period 1Element nameAtomicnumberAtomic massAtoms are split into subatomic particles (electrons, neutrons, protons)Nucleons are particles of the nucleus of the atomThese include protons (1 +), neutrons (no charge)Number of protons in element is the atomic number (ie H has 1 proton)Electrons have charge (1-) are located outside of nucleusNeutral atom, their number of electrons equals atomic number (ie. H has 1 electron)
10SUBATOMIC PARTICLES: (think parts of atoms) Protons(p): positively charged ions located in the nucleus. Number of protons=atomic numberNeutrons(n): neutral particles located in the nucleus; no charge.Use the formulaAtomic Mass - Atomic Number= # neutrons
11Subatomic Particles Continued: Electronsexist in space surrounding the nucleus in invisible shells (energy levels)electrons are transferred or shared between atoms to form chemical bondsCarry a negative ion chargeEach energy shell has electrons.First shell always has 2 electronsThan 8 electrons on each other shell.MUST REMEMBER:Atomic Number=# of protons = # of electrons in every atom
13EXAMPLE:How many protons, neutrons and electrons are found in an atom of13355CsMass number = sum of protons and neutronsNeutrons= Mass # (133) - atomic # (55) = 78There are 78 neutronsAtomic NumberHow do you get the number of protons?Protons=Atomic #How do you get the number of ElectronsElectrons=Atomic #Therefore, theAtomic number = protons and electronsThere are 55 protons and 55 electrons in Cesium.
14H 1 1 Protons: 1 Neutrons: 0 Electrons: 1 Calculate how many protons, neutrons and electrons the element Hydrogen has.Protons: 1Neutrons: 0Electrons: 1H11
15Na 23 11 Protons: 11 Neutrons: 12 Electrons: 11 Calculate how many protons, neutrons and electrons the element Sodium has.Protons: 11Neutrons: 12Electrons: 11Na2311
16Cl 36 17 Protons: 17 Neutrons: 19 Electrons: 17 Calculate how many protons, neutrons and electrons the element Sodium has.Protons: 17Neutrons: 19Electrons: 17Cl3617
17Al 27 13 Protons: 13 Neutrons: 14 Electrons: 13 Calculate how many protons, neutrons and electrons the element Sodium has.Protons: 13Neutrons: 14Electrons: 13Al2713
18Re 186 75 Protons: 75 Neutrons: 111 Electrons: 75 Calculate how many protons, neutrons and electrons the element Rhenium has.Protons: 75Neutrons: 111Electrons: 75Re18675
19REVIEW:From your knowledge of subatomic particles, fill in the chart belowElement NameAtomic #Atomic Mass# Protons# Neutrons# ElectronsAluminum12195
20Focus Questions:How does the mass of protons compare with the mass of electrons?What reason could there be for the number of protons being equal to the number of electrons in an electrically neutral atom?Is a particle an atom if it has no protons?