2 6.1 DevelopmentAntoine Lavoisier (late 1700s) organized the 33 known elements (at the time) into a list with four categoriesJohn Newlands (1864) noticed that when elements were arranged by increasing atomic mass, properties repeated every 8 elementsperiodic pattern – the law of octaves
3 Meyer, Mendeleev, and Moseley 1869-Meyer and Mendeleev both saw a connection between atomic mass and propertiesMendeleev got more credit because he was first to publish itLeft holes of undiscovered elementsPredicted properties of some undiscovered element- Sc, Ga, GeStill not completely correctMosley arranged his table by atomic number based on protons instead massfixed the problems with Mendeleev’s table
4 The Periodic LawThe statement that there is a periodic repetition of chemical and physical properties of the element when they are arranged by increasing atomic number.horizontal rows are called periodsvertical columns are called groups or families
5 The Modern Periodic Table Groups 1A through 8A = Representative Elements (a.k.a Main) because they contain a wide range of chemical and physical propertiesGroups 1B through 8B = Transition Elements
6 Classifying the elements Metalsshiny, smooth, clean, solid room temperature, good conductors of heat and electricityAlkali Metals= 1A (excluding hydrogen)highly reactiveAlkaline Earth Metals= 2Ahighly reactive (not as much as 1A)
7 Classifying the Elements Continued… Transition metalsGroup B elements contained in the D block of the tableInner transition metalsthe lanthanide and actinide seriesbelow the table
8 Classifying the elements continued Nonmetals=Generally a gas or a brittle, dull-looking solidsPoor conductorsHalogens=7AREALLY REACTIVENoble Gases= 8Aunreactive and stable (all valence electrons are filled)
9 Classifying the Elements Continued… Metalloidscontains the physical and chemical properties of both metals and nonmetal
10 6.2 Classification of the Elements The properties of each element in each group are similar because they have the same number of valence electronsThe number of the group that the element is in = the number of valence electron (excluding the transition metals)The energy level of an element’s valence electrons indicates the period on the periodic table
11 S,P,D, and F Blocks 4 different energy levels: s, p, d, and f S block= 1a and 2aholds max of 2 electronsP block= 3A through 8Amax holds 6 electronsS block must fill before P block can fillNoble gases are stable because of filled S and P blocks
12 S,P,D, and F Blocks Continued… D block = transition metalsmax of 10 electronsF block= inner transition metalsunpredictable manner of fillingmax of 14 electrons
13 6.3 Periodic Trends Electron clouds are fuzzy. So what does atomic size or radius mean?Ideas?
14 Atomic Radius How it's normally done: Take a crystal of the pure elementFind distance between adjacent nucleii
17 Atomic Radius Why do atomic radii increase as you move down a group? Why does it decrease as you move across a period?
18 Atomic RadiusThe increase from top to bottom is due to adding electron shells.The decrease from left to right is due to increased nuclear charge as you move to the right, which draws electrons closer to the nucleus.
20 Ions Atoms can gain or lose one or more electrons to form an ion. An ion is an atom or a bonded group of atoms with a positive or negative charge.
21 Ionic Radius an ion’s radius will be affected by its formation Would a cation (positive charge) be smaller or larger than the corresponding neutral atom?Would an anion (negative charge) be smaller or larger than the corresponding neutral atom?Explain ionic radii trends within periods and groups.
22 Ionization Energy Remember excited states of electrons? As energy level increases, distance from nucleus increasesAdd enough energy, the electron is no longer bound to the nucleus.Now, the atom has more protons than electrons.What's its charge?
24 Periodic Trends: Ionization Energy Ionization energy= energy required to remove an electron from a gaseous atomOctet rule = atoms tend to gain lose or share electrons to acquire a full set of 8 valence electrons
25 Periodic Trends: Ionization Energy INCREASESDECRAS
26 Ionization EnergyWhy does ionization energy tend to increase across a period?Why does it tend to decrease down a group?
27 Periodic Trends: Electronegativity Electronegativity= relative ability of an atom to attract electrons in a chemical bond.
28 ElectronegativityArbitrary units called Paulings (after Linus Pauling) are used to express electronegativity.Electronegativity increases from left to right across a period and from top to bottom down a group.Why would these trends occur?