8 th Grade 11/8 Do Now: Calcium is in period 4. It’s atomic number is 20. Draw the Bohr diagram for Calcium.

In your copybook: What pattern do you notice with the Bohr diagrams for noble gases? How does this relate to the reactivity of noble gases? What pattern do you notice with the Bohr diagrams for halogens? How does this relate to the reactivity of noble halogens? What pattern do you notice with the Bohr diagrams for alkali metals? How does this relate to the reactivity of alkali metals?

Noble Gases Do not combine with other elements All have stable outer level 8 electrons in outer level = stable for levels electrons = stable in first level

Halogens: Need 1 electron to have a stable outer energy level Flourine is the most reactive because it s outer level is closest to the nucleus Reactivity decreases down the group

Alkali Metals 1 electron in outer energy level This electron is removed during reactions Less energy is needed to remove an electron from an energy level that is farther from the nucleus Reactivity increases down the group

Electron Dot Diagrams: Symbol for the element surrounded by as many electrons as there are electrons in the outer energy level (valence electrons) Also known as Lewis Structures

The dots are written in pairs on four sides of the element symbol. How to Write Them Why do atoms combine? 1 1 Start by writing one dot on the top of the element symbol, then work your way around adding dots to the right, bottom, and left.

How to Write Them Why do atoms combine? 1 1 Add a fifth dot to the top to make a pair. For elements with more than 5 valence electrons, continue drawing dots as pairs, moving clockwise.