Unit 5 The Periodic Table
I. Development of Periodic Table Periodic law: when elements are arranged in order of increasing atomic number, their physical and chemical properties show a periodic pattern.
II. Reading the Periodic Table In each square 1. element symbol 2. atomic number 3. element s name 4. atomic mass Groups or families: elements in columns; have similar properties Periods: rows
A. Labeling & Naming Groups 3 ways to number Family Names 1A alkali metals 2A alkaline earth metals 7A halogens 8A noble gases
B. Metals, Nonmetals, Semimetals Metals on left side 1. Luster or shine 2. Conduct heat & electricity 3. Usually solids at room temperature 4. Malleable & ductile
B. Metals, Nonmetals, Semimetals Nonmetals on right side 1. No luster 2. Poor conductors of heat & electricity 3. Not malleable or ductile 4. Many are gases at room temperature; some are solids, one is liquid 5. Large variation in properties
B. Metals, Nonmetals, Semimetals Semimetals in between Also known as metalloids Properties are in between metals and nonmetals
C. Electron Configurations & Periodic Table Hydrogen 1s 1 Lithium 1s 2 2s 1 Sodium 1s 2 2s 2 2p 6 3s 1 All have one electron in the s orbital at the end. Valence electrons: outermost electrons Elements in groups are similar because they have similar valence electron configurations.
Figure 11.31: Orbitals being filled for elements in various parts of the periodic table.
D. Abbreviated Electron Configurations Atom s inner (core) electrons: represented by the nearest noble gas with a lower atomic number Li [He]2s 1 Na [Ne]3s 1 K [Ar]4s 1 Rb [Kr]5s 1 Cs [Xe]6s 1
E. The s, p, d, and f-blocks s-block: first two groups, only holds two electrons p-block: last six groups, can hold 6 electrons d-block: in middle (transition metals), can hold 10 electrons start with 3d f-block: on bottom (inner transition metals), can hold 14 electrons start with 4f
III. Periodic Trends A. Atomic radius: size of atom; distance from center (nucleus) to outer electrons 1. Atoms get larger going down a group because of increasing energy level 2. Atoms get smaller from left to right across a period because there are more protons in the nucleus to attract the electrons
Figure 11.36: Relative atomic sizes for selected atoms.
III. Periodic Trends B. Ionic size 1. Loses electrons (+) smaller than atom 2. Gains electrons (-) larger than atom
III. Periodic Trends C. Ionization energy: energy needed to remove an electron Li Li ( g ) ( g) e 1. Decreases down a group 2. Increases across a period (left to right) Small atoms hold electrons more tightly Large atoms lose electrons easily
III. Periodic Trends D. Electron Affinity: energy change when an electron is gained (+) electron affinity requires energy (-) electron affinity no energy required (loves electrons) 1. Nonmetals usually negative (most) 2. Metals small negatives or positive 3. Noble gases all positive
III. Periodic Trends Octet Rule: atoms tend to gain, lose, or share electrons in order to acquire a full set of valence electrons. (2 in s, 6 in p of highest energy level)
III. Periodic Trends E. Electronegativity: attraction of electrons to atoms involved in a bond Flourine has most (4.0) Cesium & francium least (0.7) 1. Increases from left to right across a period 2. Decreases down a group