Periodic Table and Chemical Bonds Review Periodic Table

Periodic Table and Chemical Bonds Review

Periodic Table • Organized by increasing atomic number (number of protons) • Groups (columns) – shared properties and electrons in the outer shell • Periods (rows) – represent a new electron shell (layers, like an onion) • Remember that atoms are made of: • • • Protons (positively charged particle, in the nucleus, adds mass) Neutrons (neutral particle, in the nucleus, adds mass) Electrons (negatively charged particle, outside the nucleus) Protons and electrons usually balance each other’s charge If an atom has gained or lost electrons, the balance is lost and it becomes an ion

Metals vs. Non-metals • Properties of metals (including alkali, alkaline earth, and transition metals): • • Luster (shiny) Ductility (stretchy) Malleability (bendy) Conductivity • Properties of non-metals: • Opposites of metals

More on non-metals and metalloids • Metalloids: • have properties of both metals AND non-metals • Can act as semiconductors at high temperatures • Non-metals • Include elements in the upper right corner of the periodic table (carbon, sulfur, phosphorus) • Halogens – highly reactive gases next to noble gases • Noble gases – unreactive gases on the right side of the periodic table

Electrons and Energy Levels • Each period represents a new shell (layer) of electrons • The outermost layer is called the valence shell • Valence electrons have higher energy than previous layers • Valence electrons are what interact to form bonds between atoms

Bonds • Covalent bonds are like a handshake between two atoms, where each atoms shares an electron with the other. • Sometimes one of the atoms pulls the electrons closer to itself (it doesn’t share the electrons equally) causing one side of the molecule to have a charge. This molecule is now a polar molecule – it has a positive (+) and a negative (-) pole. Water is polar and water molecules stick to each other • Ionic bonds are when atoms “trade” electrons and become ions (atoms that have charge) and because they have positive (+) and negative (-) charge they stick to each other