41b: groups of the Periodic Table Metals:Good conductorsSolid (except mercury)Lose electronsExample = aluminumSemi-metals (metalloids):Have properties of both metals and non-metalsCommon use =semi-conductorsExample = siliconNon-metals:poor conductorsMostly liquid/gasgain electronsExample = nitrogenHalogens:Extremely reactiveGain 1 electronMostly gasesExample = fluorine
5Summary 2 Describe the differences between metals and non-metals. Give an example of a metalGive an example of a non-metal
61c: Periodic Groups Alkali metals Transition metals Extremely reactive Lose 1 electronExample: sodiumAlkaline earth metalsReactiveLose 2 electronsExample: calciumTransition metalsCan lose different numbers of electronsExample: copperNoble gasesExtremely un-reactiveGases!Example: helium
7Summary 3Which group of metals are most reactive?
81a: organization of the periodic table The Periodic Table: organizes elements in groups and periods.Groups/families: elements have the same physical and chemical properties.Rows/periods: elements have the same number of electron shells.
9Summary 4Name another element that would have similar chemical properties to chlorine.Name an atom that is in the same period as chlorine.
10C The Periodic Table: organizes elements according to atomic number Atomic number = number of protonsAtomic number6C12.01112345678910
11MassMass number: the number of protons and neutrons in an atom (units = amu)Atomic mass (shown on the periodic table): the average mass of all isotopesIsotope: an atom with the same number of protons and a different number of neutronsNote: atomic mass generally increases across the periodic table but not always… (look at atomic number 27&28, 52&53)
13Summary 5What is the mass number for each isotope of neon shown in the example?What is the atomic mass for neon?
14Standard 1d: electronsAll atoms have an equal number of protons and electronsAtoms are electrically neutralAtoms have no chargeSymbol: NeAn equal number of positive protons and negative electrons results in zero charge
15Summary 6How many electrons are in a magnesium atom?
16When an atom gains or loses electrons it becomes an ion Ion = charged particlenumber electrons ≠ number protonssymbolsymbolNaNa+
17Summary 7If a magnesium atom loses two electrons, how many electrons will this magnesium ion have?
18Valence electrons are: responsible for chemical behavior of atom used for chemical bondinglocated in the outer orbital1 valence e valence e-
19Summary 8 How many valence electrons does nitrogen have? How many total electrons does nitrogen have?
20Identifying Atoms by Emission Spectrum: Adding energy ‘excites’ electrons.Electrons release energy when they return to the ‘ground state’ (lowest energy level)Released energy = ‘emission spectrum’Each atom has a unique emission spectrumScientists use this information in many ways:CSI can identify elements in an unknown sampleAstronomers can identify elements in stars across the universe
221c: Periodic TrendsElectronegativity: The ability of an atom to attract an electronExample: chlorine is very electronegative because it wants to ______ an electron.Example: sodium is not very electronegative because it wants to ______ an electron.
23General trend for electronegativity: Increasing electronegativityIncreasingNote: for noble gases electronegativity = zero
24Summary 10 Which is more electronegative: iodine or chlorine? Which is more electronegative: argon or chlorine?
25Ionization energy: the energy needed to remove an electron from an atom Example: fluorine has a high ionization energy because it wants to ______ an electron.Example: potassium has a low ionization energy because it wants to ______ an electron.
26General trend for ionization energy: Increasing ionization energyIncreasingNote: noble gases have a high ionization energy
27Summary 11 Which has a higher ionization energy: iodine or chlorine? Which has a higher ionization energy: argon or chlorine?Which has a lower ionization energy: chlorine or magnesium?
28General trend for atomic size (volume) Decreasing atomic sizedecreasingIncreasing
29Summary 12 Which is larger: magnesium or calcium? Which is larger: magnesium or chlorine?
30General trend for ionic size. When atoms lose electrons they get much smallerWhen atoms gain electrons they get much larger
32Standard 1e: The structure of an atom All the mass of an atom is in the nucleus (Protons & neutrons are in the nucleus)In between the nucleus and the electrons there is only empty space
33Summary 14Which particles inside the atom have mass?
34Earnest RutherfordRutherford demonstrated that the entire atom is 10,000 times larger than the nucleusThe rutherford experiment:A stream of positive particles (alpha particles) is aimed at a piece of gold foil.Only 1 in 8000 particles is deflected (pass close to the gold nucleus).All other particles travel through ‘empty space’Rutherford’s gold-foil experiment yielded evidence of the atomic nucleus. a) Rutherford and his coworkers aimed a beam of alpha particles at a sheet of gold foil surrounded by a fluorescent screen. Most of the particles passed through the foil with no deflection at all. A few particles were greatly deflected. b) Rutherford concluded that most of the alpha particles pass through the gold foil because the atom is mostly empty space. The mass and positive charge are concentrated in a small region of the atom. Rutherford called this region the nucleus. Particles that approach the nucleus closely are greatly deflected.
35Summary 15How does Rutherford’s experiment demonstrate that an atom is mostly empty space?