1. Periodic trends 10/23/15

2. Atomic mass Atomic Mass: the average mass of one atom of an element measured in amu Generally the atomic mass increases down a group and from left to right As the amount of protons and neutrons increase, so does the mass

3. Atomic radius Atomic radius: the distance from the center of the atom to the outer edge measured in Å Radius increases down the group – More energy levels causes volume to increase Decreases across the period – Same energy level but more protons pull electrons closer and decrease the volume

4. Ionic radius When an atom looses an electron to become positively charged, its radius decreases – More protons than electrons so strong attraction to the nucleus When an atom gains an electron to become negatively charged, its radius increases – More electrons than protons so less attraction to the nucleus

5. Ionization energy Ionization energy: the amount of energy it takes to remove an electron measured in V Decreases down a group – Bigger size atom makes it easier to remove electrons Increases across a period – Smaller size atom makes it harder to remove electrons

6. Electronegativity Electronegativity: within a covalent compound the pull an element has for the bonded electrons Generally decreases down a group – Attraction for electrons in a bond is difficult because of larger size Increases across period – Smaller size makes easier to attract electrons Noble gases don’t have electronegativity values because they don’t form compounds

7. Density Density: the mass per volume measured in g/mL Doesn’t have as nice of a pattern Mostly increases down group Varies because of differences in mass and volume trends. D=m/V

8. Melting point Melting point: the temperature the element goes from a solid to a liquid in K Mostly decreases down a group Increases across metals and decreases across nonmetals Many different factors affect melting point mostly related to the attraction between particles of the substance