Atoms and Bonding

1. Atoms and Bonding What determines an element’s chemistry

2. When atoms combine they form compounds. • Electrons of an atom are found in different energy levels. • Valence electrons are the outermost electrons in an atom .They have higher amounts of energy • Valence electrons in an atom determine the element’s chemical properties. • The term “valence” comes from the Latin word valentia, meaning power.

3. How many electrons are in a neutral atom? The same number as the number of protons. • How are an atom’s valence electrons different from the rest of the atom’s electrons? The valence electrons have the highest energy. • Why are valance electrons important? They are involved in forming chemical bonds • What is a chemical bond? The force of attraction that holds two atoms together as a result of the arrangement of electrons between them. • Valence electrons in an atom. The outermost electrons, are represented by an electron dot diagram. See figure 1 ,page 359. How many valence electron Hydrogen has? Carbon? Oxygen?

4. Applying the periodic table • The elements in the periodic table are in order by increasing atomic number • The number of valence electrons increases from left to right across each period. • Each period begins with an element that has 1 valence electron and ends with an element that has 8 valence electrons.(Period 1 is the exception ending with Helium which has 2 valence electrons). • Thus, group 1 elements ( alkali metals) have 1 valence electron. Group 2 elements ( alkaline earth metals) have 2 valence electrons. Group 3 –group 12 (transition metals) is an exception to the rule and uses the “d electron count method” an electronic configuration. Group 13 elements have 3 valence electrons. Group 14 elements (Carbon family) have 4 valence electrons; Group 15 elements (nitrogen family) have five valence electrons; Group 16 elements (oxygen family ) have six valence electrons. Group 17 elements (halogens) have 7 valence electrons. Group 18 elements(noble gases) have 8 valence electrons. • Look figure 2,page 360 periodic table of elements.

5. An important distinction between metals and non metals is how their valence electrons form bonds. • Metals lose electrons when they bond with other atoms. The reactivity of a metal depends on how easily its atoms lose valence electrons. • Nonmetals become stable when they gain or share enough electrons to have 8 valence electrons.

6. Metalloids have some properties of metals and some properties of nonmetals. • When metalloids combine with other elements what happens to their valence electrons? They either lose or share them • How is this similar to metals? Metals lose electrons when they combine with other elements. • How is this different from metals? Metals do not share electrons.