Atoms, Elements and the Periodic Table By: Mrs. Herman 2013
Made of A t o m s Protons (positive charge) Neutrons (neutral charge) Electrons (negative charge) Each atom contains a specific number of protons in its nucleus. https://io9.gizmodo.com/the-first-image-ever-of-a-hydrogen-atoms-orbital-struc-509684901
Atoms with different numbers of protons, neutrons and electrons have different properties. Gold, AU
Modern Atomic Theory
Democritus Democritus proposed that matter cannot be broken down indefinitely. At some point you end up with a piece that can t be divided. That smallest piece he called an atom, from the Greek word atomos, which means indivisible. 470-380 B.C.
John Dalton John Dalton was a British chemist. He was the first modern scientist to propose the existence of atoms. He described an atom as an invisible indestructible, solid sphere, like a billiard ball. The Indivisible Sphere 1766-1844
Sir Joseph J.J. Thomson 1856-1940 J.J. Thomson was a British physicist who was the first scientist to propose the plum pudding model. He was also the first to propose the theory of the negatively charged electron. He was credited for the discovery. He also proposed the isotope.
Ernest Rutherford Ernest Rutherford experiments proved that atoms are mostly empty space Discovered the nucleus, which contains positively charged particles. He was the first to suggest that electrons circle the dense nucleus. 1871-1937
Niels Bohr Niels Bohr stated that electrons move in different orbits, or energy levels, around the nucleus like planets orbit the sun. Each energy level is located a specific distance from the nucleus and contains a certain number of electrons. 1885-1962
Current Atomic Model Electron Clouds This model is based upon Bohr s model, except that electrons orbit the nucleus in random patterns. The region where these particles are found is referred to as the electron cloud. Nucleus
What is an element? A substance that consists of just one type of atom
Elements 115 different types of atoms 115 different types of elements
Demitri Mendeleev Demitri Mendeleev was a Russian scientist. He was the first person to make the periodic table.
Mendeleev s Table
The periodic table is a chart of the elements arranged into rows and columns according to their physical and chemical properties.
How to Read the Table Atomic Number = number of protons in the atom Chemical Symbol 6 C carbon Element Name 12.01115 Average Atomic Mass
The Periodic Table A group a column on the table A period a row on the table Metal ¾ of all elements are metals, all are shiny and conduct thermal energy and electricity. Metalloid have properties of both metals and nonmetals Non-metal many are gases and except for hydrogen are on the right of the table Nobel gases element in group18 on the table (stable). Synthetic created by man
Substance Always made of the same combination of atoms Elements A substance made up of just 1 type of atom Compounds A substance containing atoms of 2 or more different elements chemically bonded together
Molecules vs. Compounds A molecule is formed when two or more atoms join together chemically. (Examples = H 2 O, O 2, O 3 ) A compound is a molecule that contains at least two different elements. (Examples = NaCl, H 2 O) All compounds are molecules but not all molecules are compounds.
Mixture Two or more substances that are physically blended but not chemically bonded. Heterogeneous A mixture in which substances are not evenly mixed. Homogeneous A mixture in which two or more substances are evenly mixed. Also called a solution.
What is ph? The ph is an inverse measure of the concentration of hydronium ions (H₃Oᶧ) in a solution.
Acids An acid is a substance that produces a hydronium ion (H₃Oᶧ) when dissolved in water. Examples of acids include milk, vinegar, OJ, and battery acid Properties of acids include; Providing a sour taste Many can damage skin or eyes React with metals
Bases A base is a substance that produces hydroxide ions (OH ) when dissolved in water. Some examples include detergents, antacids, baking soda, shampoo, window cleaner. Some properties of bases are; Provide a bitter taste Most damage skin or eyes Bases are slippery when mixed with water
The ph Scale The ph scale is used to indicate how acidic or basic a substance is. It ranges from 0 to 14 with neutral substances at a ph of 7.
The ph Scale
Salt Most of the salts are crystalline solid Salts may be transparent or opaque, colorless or colored Most of the salts are soluble in water Solutions of salts conduct electricity The salt may be salty, sour, sweet, or bitter