### PERIODIC TABLE OF ELEMENTS

1. PERIODIC TABLE OF ELEMENTS Module 3 Enhanced Science Grade 8
2. Elements Known Throughout History:
3. JOHANN DOBEREINER (1817) • a German chemist who formed the triads of elements with similar properties.
4. JOHN NEWLANDS (1863) • an English chemist proposed the Law of Octaves. • He based his classification of elements on the fact that similar properties could be noted for every eight element when they are arranged in order of increasing atomic masses.
5. Lothar Meyer and Dmitri Mendeleev • They both came up with periodic tables that showed how elements should be grouped. • Both scientists were teachers living and working in different places. – Meyer lived and worked in Germany – Mendeleev in Russia. • Both arranged the elements in order of increasing atomic mass while putting in groups those with similar properties. • Both of them also left blank spaces in their tables, believing that these spaces would be filled later with elements yet to be discovered.
6. Dmitri Ivanovich Mendeleev • Father of the Periodic Table • He noticed patterns in the properties and atomic weights of halogens, alkali metals and alkaline metals. • In an effort to extend this pattern to other elements, he created a card for each of the 63 known elements. • he developed his statement of the periodic law and published his work. • One vote shy of being awarded the Noble Prize for his work in chemistry.
7. Mendeleev’s Table (in German)
8. Henry Moseley (1914) • an English physicist observed that the order of the X-ray frequencies emitted by elements follows the ordering of the elements by atomic number. ** This observation led to the development of the MODERN PERIODIC LAW which states that “the properties of elements vary periodically with atomic number.”
9. MODERN PERIODIC TABLE ---organizes elements in such a way that information about the elements and their compounds are easily revealed
10. MODERN PERIODIC TABLE • The vertical columns of the periodic table, called GROUPS, identify the principal families of elements. Some families have their special names.
11. MODERN PERIODIC TABLE • The horizontal rows or PERIODS are numbered from the top to bottom. Examples: the elements lithium (Li) across neon (Ne) form Period 2.There are 7 horizontal rows or periods in the periodic table.
12. MODERN PERIODIC TABLE • The elements are grouped into blocks or series in the periodic table. Group 3 to Group 12 constitutes one block wherein elements in this block are referred as the transition elements. The lanthanides and actinides are special series of elements but are also part of the transition block; they are also called the inner transition elements. Elements from the taller columns (groups 1, 2, and 13 through 18) are called the representative elements or main groups of the periodic table.
13. Types of Elements 1. Metals: elements that have luster, are malleable and ductile, and are good conductors of heat & electricity. (left, in blue) 2. Nonmetals: elements that are usually brittle solids or gases at room temperature and poor conductors. (right, in yellow) 3. Metalloids: elements that share some properties with metals and some with nonmetals. (stair-step, under gases, in green) 4. Representative elements: columns 1 & 2, 13 – 18 5. Transition elements: columns 3 – 12 6. Inner Transition elements: below the main table
14. REACTIVITY The ease and speed with which a metal reacts with another substance. • Metals vary in reactivity. • The most reactive metals will react even with cold water while the least will not react even with acid. • The reactivity of metals can cause deterioration of materials. **The gradual wearing away of a metal due to interaction with other substances is called CORROSION.
15. REACTIVITY • Metallic character increases from top to bottom and decreases from left to right; • nonmetallic character decreases from top to bottom and increases from left to right, as seen in the figure on the right.
16. LOSE AND GAIN OF ELECTRON • Metallic property relates to how easy it is for an atom to lose an electron. • nonmetallic property relates to how easy it is for an atom to gain an electron. ** when an atom loses electrons, a cation is formed. **some nonmetals, tend to gain electrons thus forming anions. **The formation of ions among the elements results in the formation of many different compounds.
17. ELECTRON SHELLS where electrons occupy regions around the nucleus called electron shells. These are also called energy levels because each electron shell corresponds to a particular energy. Each electron shell can hold only a certain number of electrons. The way the electrons of an atom are distributed in the various energy levels or electron shells is called ELECTRONIC CONFIGURATION.
18. VALENCE SHELL • The highest energy level that an electron occupies is referred to as the outermost shell or VALENCE SHELL. • The electrons in the valence shells are called VALENCE ELECTRONS. These electrons are the ones involved in chemical reactions. The chemical properties of an element depend on the number of valence electrons
19. FAMILIES OF ELEMENTS
20. Alkali Metals: Group 1 (1a) • Silvery solid; soft compared to other metals • Low density and low melting point • Extremely reactive; especially in water • 1 valence electron • Very easy to lose 1 electron • Reactivity INCREASES as you go down the family. • Francium is much more reactive than Lithium. • Hydrogen is not a metal but is grouped here because of its number of valence electrons.
21. Alkaline Earth Metals: Group 2 (2a) • Denser, harder, higher melting point than group 1 • Conducts electricity well • Very reactive but not as much as group 1 • 2 valence electrons – Easy to lose 2 electrons • Reactivity INCREASES as you go down the family. • Radium is much more reactive than Beryllium.
22. Boron Family: Group 13 (3a) • Metals except for Boron, which is a metalloid • These elements are used in a variety of products • Reactive; Bonds with other elements by sharing electrons. • 3 valence electrons – Needs to lose 3 electrons • Reactivity INCREASES as you go down the family. - Thallium is more reactive than Boron.
23. Carbon Family: Group 14 (4a) • Metals, nonmetals, and metalloids • Bond with many elements by sharing electrons • Silicon is a semiconductor: – Extremely abundant metalloid – Used in computer chip manufacturing – “Silicon Valley” • 4 valence electrons -Lose 4 or gain 4; same difference
24. Nitrogen Family: Group 15 (5a) • Metals, Nonmetals, and Metalloids • Reactive: Bonds with other elements by sharing electrons • Useful to living things in small amounts; deadly in large amounts • 5 valence electrons – Needs to gain 3 electrons • Reactivity DECREASES as you go down the family. – Nitrogen is more reactive than Bismuth.
25. Oxygen Family: Group 16 (6a) • Nonmetals and Metalloids • Oxygen & Sulfur are essential for life; Selenium conducts electricity when exposed to light • Very reactive • 6 valence electrons – Easy to gain 2 electrons • Reactivity DECREASES as you go down the family. • Oxygen is more reactive than Polonium.
26. Halogens: Group 17 (7a) • Nonmetals, except Astatine (radioactive metalloid) • Halogen means “salt-former” • Highly reactive • 7 valence electrons – Very easy to gain 1 electron to fill shell • Reactivity DECREASES as you go down the family. 1. Fluorine is extremely reactive, whereas Iodine is the least reactive.
27. Noble Gases: Group 18 (8a) • Nonmetals • Inert; they do not react with other elements • Used in various types of lighting • 8 valence electrons (orbital is full) • Helium is less dense than air and is used in all types of balloons. • Helium is safer than hydrogen, because Hydrogen catches fire.
28. Transition Elements: Groups 3 – 12 • All are metals; shiny, hard, lustrous • Most are found combined with other elements in ores • Most have higher melting pts than Representative E • Mercury is the only liquid at room temperature Transition Elements (in yellow) • Special groups: (‘group’ does not refer to a column.) 1. Iron Triad: Iron, Cobalt, Nickel 2. Platinum Group: Ruthenium, Rhodium, Palladium, Osmium, Iridium, Platinum
29. Inner Transition Elements A. Found below the main table. B. Lanthanides: naturally occurring except Promethium 1. Soft metals; can be cut w/a knife 2. Very similar; hard to separate when together as an ore C. Actinides: synthetic (except Thorium, Protactinium, Uranium) 1. Radioactive 2. Unstable nuclei; decay to form other elements